Greywater without land. A five stage, activated sludge greywater system in drums.

Greywater treatment system made from 55 gallon drums. This is, essentially, a five stage, activated sludge greywater system. The greywater is biologically processed to be recycled for decorative landscaping.

Rather than writing a general "how-to" for this type of greywater system, I'll start with a "this is what I did" type of article.

Assess the clients needs[edit | edit source]

This client lives in a high drought area of Northern California whose well runs dry during the summer months of the year. Large storage tanks buffer the year round water requirement of the property. However, water still has to be trucked in several times during the dry season. The purpose of this greywater system is to minimize the impact of irrigating a half acre of decorative landscaping surrounding the house by recycling the used water. Depending on the weather, an estimated 100-200 gallons per week is needed for landscaping. The system needs to be low maintenance, easy to use and have enough storage for regular waterings. And supply 100% of the landscaping hydration needs during the drought season.

Topographical Study[edit | edit source]

The house is two stories. Greywater produced on the second floor has enough head to gravity feed the complete treatment process of the planed system. The first floor drains are too low for a gravity feed greywater system and will not be part of the this treatment plan. The second floor has a large kitchen with a dishwasher, a clothes washer, and two bathrooms. The first floor has a small kitchen and one bathroom. Most of the greywater potential is produced on the second floor.

Diverting the Greywater[edit | edit source]

All the second story greywater drains were replumbed into a common pipe. A wye valve was installed to direct the greywater to either the greywater treatment system or the septic system. In the picture below, the two valves determine where the water flows. The left valve (at the center of the picture) drops down into the septic. The right valve directs to the greywater treatment system. Any greywater retrofit should maintain the option to revert to the original system.

If the residents have a need to use chemical cleaners that will go down the drain, having the option to switch to septic will save the health of a biological greywater treatment system. Also, if the greywater system requires maintenance, it's really nice to not have second hand water flowing at you. This greywater system is turned off during the rainy months. When installing any plumbing, follow the local codes. Most of them are there for really good reasons. This retrofit maintains all the required pipe ventilation and meets or exceeds the minimum pipe slope requirements. Somewhere online I researched the California Residential and Commercial Standards. These standards require that any pipe diameter less than or equal to 2" have a slope of 1/4" fall/foot. And any pipe diameter greater than or equal to 3" have a slope of 1/8" fall/foot.

OccGW UnderHouse.jpg

From the wye valve the greywater travels down a 4" pipe to the processing chambers (45-gallon drums) in a retired chicken coop.

To allow for the cap of the first drum to open, the downspout rotates upward and out of the way via a set of mated male and female threaded pipe adapters incline on the 4" pipe. They're threaded loose enough to rotate easily and tight enough so that its friction keeps the downspout in the desired position.

The downspout is designed to create a fairly tight seal with the drum's lid. I wanted to minimize the potential for unforeseen outside influences that could foul the system.

Greywater Treatement[edit | edit source]

OccGW CentralSystem.jpg

This is the heart of the greywater treatment system. Greywater enters from the downspout on the left and gets progressively cleaner as it's pushed through each drum from left to right.

For the most part, a healthy flora of aerobic bacteria is what does the cleaning. After an initial seeding of beneficial bacteria, heavy aeration is required to keep the system functioning well. The first drum, containing the dirtiest water gets the heaviest aeration. My target rate for the first two drums is 300 Liters per hour (Lph). That is about 7.5-Lph per gallon of water, which is close to the target aeration rate for municipal activated sludge sewage treatment systems. The next two drums are receiving about 240-Lph, or 6-Lph/gal.

One way that this system differs from a typical activated sludge system is that there is no separate settling period. Debris from the house drains and large flocs settle to the bottom of each drum. Part of the regular maintenance is to drain the sludge that collects at the bottom of each drum two or three times a summer. In the picture below, the 2" plumbing and valves make this maintenance easy. One at a time, open each valve for about 10-15 seconds. At the bottom of each drum, an industrial sized floor drain has been installed. A few feet of water pressure, large drains and drain pipes creates decent suction and the sediment gets sucked away. The drains lead to an old oak tree nearby.

OccGW Last3Drums.jpg

Side Note

In writing this, I have thought of an improvement to this combined aeration/settling system. As it is, water on the out of this system is fairly clear. But to improve it further, when I get a chance, I'm going to lift the air stone from the bottom, progressively higher in each drum. The aeration from the air stones create considerable turbulence (check picture below) at their flow rates so only the largest flocs and debris settle to the bottom. A non turbulent region below the air stones would allow for more settling and cleaner water on the out. In the first drum, I'll lift the stone only a few inches. The deeper the aeration, the greater dissolved oxygen concentration because of increased water pressure and the contact time the bubbles have with the water before reaching the surface. I'll raise the air stone about 6-inches in the second drum and about 12-inches in the last two drums. I haven't calculated it, but I'm guessing that the high O2 flow rate in these drums will make the difference in height fairly negligible. The upward motion of the air bubbles will maintain a water flow cycle through the drum that will continuously carry oxygenated water from the top down below the aerator. So below the aerators water will continuously flow but the turbulence above wont keep the larger flocs from settling. ADDENDUM: Raising the air stones as described improved the clarity of the water output, and doesn't seem to have any drawbacks.

OccGW OpenDrum12.jpg


Water transfer from drum to drum through 1-inch irrigation pipe pushed through a 15/16-inch hole and an 90-degree elbow (see the elbow between the two drums below). It takes some force to get the irrigation pipe through but the seal is water tight and it saves the cost of expensive bulkhead fittings, which are typically used to tap a hole in a tank. Additionally, these holes are drilled on the curve where the drum starts tapering to the lid. Being on the curve forces the irrigation pipe to slant downward into the water, minimizing the chance for oils and surface scum to transfer from drum to drum. And since flocs tend to sink rather than float, there's less chance that they will flow up the irrigation pipe into the next drum.

OccGW FirstDrum.jpg

In the last drum, the water exits into another irrigation pipe, this one slanting upward (see in picture below at right). It leads to the 500-gallon storage tank. The opening at this pipe is set higher than all the other drum-to-drum pipes and sets the water level in all the drums. As greywater flows into the system from the house, water is pushed progressively through the system and exits at the surface of the final drum. Currently this pipe is skimming the surface of the last drum, which is fairly processed and clean, but I think I'll put an elbow on this pipe to pull water from an inch or two below the surface instead.

OccGW AirTubes.jpg

The water flows out of the chicken coop to the 500-gallon storage tank about 30-feet down the hill. Here you can see the drum to storage tank pipe, the maintenance drain, the return pipe for pressurized, treated greywater leading back to the house and the aeration hose coming to the drums.

Greywater Storage[edit | edit source]

Here's where the water from the drums enter the storage tank. The other pipe is the overflow drain, currently leading to the old oak tree as well. But, since the overflow is treated, I'm thinking about plans to direct it to a series of currently unused garden ponds nearby. The first small pond will serve as an ornamental wetland treatment for the water before flowing into a larger pond nearby.

Hardware[edit | edit source]

The Storage tank is also oxygenated to maintain aerobic conditions, keeping the water 'healthy' until used for landscape irrigation. The storage tank is being aerated at a rate somewhere around 2300 Lph. About 4.5-Lph/gal. It has been over a year since the current system has been built and I'm very happy with the performance of the air pump. It's an Airtech 40 Pond Aeration pump. They claim that they make the most efficient air pumps on the market and it's the only company I could find that openly publishes their performance curves. You can see it mounted to the top of the flotec well pressure tank. Coincidentally they match. The Airtec isn't UL approved for outdoor use so you see it with my makeshift pump housing which protects it from any water that might leak from the roof of the aviary and doubles as a baffle to keep dust from entering the pump's air filter. Hopefully the air filter will last longer because of it. The housing is a cut down 5-gallon bucket mounted on lamp hardware which keeps it from touching the vibrating pump. The pump is fairly quiet unless there is something to vibrate against.

OccGW StoragePumps.jpg

The system shown here at the storage tank out flow is a Flotec ¾-hp jet pump, a Flotec 40-gal pressure tank providing continuous 30-50 psi water pressure to a couple greywater designated spigots back up at the house for irrigation.

OccGW JetPump.jpg

I have recently added a float switch and a separate cut-off switch to the jet pump. The float switch is shown in only about 10-inches of water. It's tethered to open the circuit when the water level goes down to about 4-inches. It doesn't close the circuit until the water level fills back up to about 10-inches.

Repairs[edit | edit source]

Recently, the greywater flow got switched to the septic system for some maintenance, but wasn't switched back after the maintenance finished. Irrigation continued as normal, draining the storage tank and the jet pump ran for two days without water. It got hot and melted the PVC adapters going in and out of the pump. Fortunately, the pump didn't need to be replaced because it has a built-in temperature switch that shuts off before it's own components melt or burn out. Only the plumbing surrounding the pump had to be replaced. The float switch simply cuts the power to the pump if the tank gets too low, preventing this type of problem in the future. I installed the manual cut-off switch to the jet pump as well after realizing that any maintenance required for the jet pump meant turning off the power to the air pump as well. Now aeration of all the drums and storage tank doesn't have to be interrupted if any work is required on the jet pump. The picture (above right) shows the master switch and outlet powering the air pump above and jet pump switch box below. The float switch is wired in line at this lower switch box. The manuals for all the equipment are zip lock bagged and stapled to the wall in for convenience in case anyone less familiar with the system needs to work on it in the future.

Replacing the plumbing for this problem was a fairly simple task, thanks to some preplanning when the system was built. Looking back at the jet pump detail picture, the red valve at the tank out-flow allowed me to work on the plumbing without losing any more water from the tank. And, the quick connect adapters (grey, larger diameter) before and after the pump allowed for replacement of only the sections damaged by overheating. Also, the coupled male-female threaded pipe adapters before the pressure gauge kept me from having to replace the whole gauge assembly. Coming back to the air pump, when designing the pneumatic plumbing to the air stones, using irrigation pipe seemed to be the most cost effective way to cover the, close to 50-foot, distance. In the picture below the irrigation tubing (in need of a pipe clamp) is pushed onto the air pump nozzle.

OccGW AirPumpOut.jpg

Air Distribution[edit | edit source]

From the irrigation tubing, I used a barb hole punch and standard 1/8" drip irrigation barbs to tap into the tubing. From there I used the more expensive vinyl tubing typically used for airstones. Most of the airstones have 1/4" nipples. I saved on adapters by just pushing the 1/8" vinyl tubing into 1/4" vinyl tubes as you can see in the picture below. The first airstone is larger with a 3/8" nipple.

OccGW Pneumatics.jpg

It is certainly not the most elligant and likely has some minor leaks but it works.

Maintenance Schedule[edit | edit source]

Monthly[edit | edit source]

Once a month open the first two drums and scoop out any oils that have collected with a pool skimmer. Most of it is in the first drum and the second drum usually just has a couple traces.

Every other month[edit | edit source]

As mentioned prior, suck out the sediment at the bottom of the drums. Open each valve, one at a time, for 5-10 seconds. Clean the airstones. Turn off the air pump. Pull the airstones up and out of the drums and tanks. Soak each airstone for a minute or two in muriatic acid (pool filter cleaner) using a plastic container (it etches glass). Eye and skin protection required. Read the label.

Beginning of season[edit | edit source]

Visually inspect all plumbing, electrical wires and the jet pump. Clean or replace the air filter on the air pump. Switch drain valves from the septic to the greywater system.

Turn the power on to the system.

Seed the system with beneficial aerobic bacteria. One bottle of K-87 is enough (see below). When the first drum is at least half full, pour a few tablespoons in. Seed the system again when water reaches the storage tank by pouring the bottle evenly between the four drums. I have been using Roebic Laboratories K-87 soap digester. The local hardware store stocks several Roebic products. When I first started building this system, I called the company up and asked which of their products contain the most aerobic digestive bacteria. K-87 was their answer. Looking at their website now, it looks like they may have added the perfect product to their line, Air-O-Pak.

At the end of the season[edit | edit source]

Switch drain valves to the septic system.

Clean the airstones.

Scrub down the walls of each drum and storage tank with a long-handled brush. Drain drums and storage tank completely. Leave them open until completely dry, then close it all up until next drought season. Shut the power to the system.

Potential Improvements[edit | edit source]

I'm considering adding some bacterial media to the last two drums, creating significantly more surface area for the bacteria to adhere to. Low operation cost and easy maintenance are the requirements for this system. One idea I heard about, that I like and am considering, is to reuse old plastic drink bottles. The bottoms need to be cut off so that the flow of aerated water can pass through. Smaller bottles have more surface are to volume than larger bottles. Throwing the bottles directly in the tanks would make cleaning and maintenance a hassle. I'm wondering if large (around 10-gallon) plastic mesh bags are available, like a larger version of what onions are often sold in at the supermarket. Filling one of those with bottomless plastic bottles and hanging them in the drum from a hook fastened to the lid might work well. It would be easy to remove and easy to replace. And the empty bottles cost nothing.

Water Quality Test[edit | edit source]

I finally got around to having the greywater effluent laboratory tested. I sampled the greywater from the hose that is used to water the landscaping after letting it run for about 5 minutes. I let the water run in order to clear out any stagnant water that may have been sitting in the hose and plumbing.

I chose three tests that would give a pretty good idea of the overall water quality, Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), and a Fecal Coliform count. I would like to have had a Total Coliform count, as well as conducting all four tests on the greywater before it went through the system for comparison. But the three tests alone cost $150US, so I compromised. The tests were taken on September 5th, 2007; The end of summer. The well at this property had been dry for a couple of months and potable water was being purchased. So the household was being very conservative with their water use. Generally, being conservative means less dilution of the dirts and soaps going down the drain into the greywater system. So we can assume the water being treated was dirty. I don't know how dirty because I have never tested it; It was probably worse than normal and much worse than what the result show here for the treated water.

Laboratory Results[edit | edit source]

Analysis Results
BOD5 @ 20 degrees C mg/L (Std. Mthds. 20th ed. 5210) < 5.0
COD mg/L (HACH 8000) 32
Fecal Colifom MPN/100ml 23

I apologize for not having done the research to tell you what these numbers mean. If any of you reading this are familiar with water quality testing and could offer your expertise, it would be appreciated.

Discussion[View | Edit]

Welcome[edit source]

I get notified whenever this page is edited. I encourage you to post your ideas, comments and criticisms here; If something has caught your interest, it's likely that others would benefit from the resulting post/discussion.

If you feel the need to contact me personally about this project, use this email: goodsignal at appropedia dot org

Regards, Gabe. -GoodSignal 13:21, 16 June 2007 (PDT)

Initial comments[edit source]

This is great! I am so excited to see the details that go with this awesome outline. I wikified the outline (to the 4th level deep), although maybe it should be wikified deeper (just keep adding ='s). What do you think? Maybe it is easier for you to work the other way, so the text outline is still at the bottom, and you can always just revert to your last save.

Thank you for getting this going, it is a great addition to the knowledge base on home greywater systems. --Lonny 11:58, 14 June 2006 (PDT)

who is the contact[edit source]

I am interested in finding out more about this project. I live in santa rosa, not far from occidental. I would like to talk to the person, or group, who did this project.

thanks Mandeep

power consumption of the air pump[edit source]

I called airtech and gathered some info about the air pump. I am assuming you used the JP40C. Its rated at 300 watts. Assuming that this is the only air pump used to supply all the aeration needs (both the drums and storage tank) and that it runs 24/7, it comes to about (300 x 24 x 30 ) 216Kwh per month. Lowest rate for 1kwh in our area is about 11 c. So it costs about $23.76 per month to run this pump. Could be more if you cross into higher tiers.

I am interested in recycling grey water but storing it in a pond. Any idea what type of aeration pump will do for just the 4 drums.


Does the pump HAVE to run 24/7? Seems like overkill, and a huge energy user (couldn't be practically used on off-grid alternative energy systems, it would need at least a 1000 watts worth of solar panel. not cheap.) --Naught101 17:30, 12 January 2008 (PST)
I think this calls for a page on non-mechanical methods of aerating water - e.g. allowing the water to run over gravel, or a tiered waterfall (making sure there's proper spacing to allow splashing). Don't know how effective it would be, and of course it depends on how much height difference is availablebut it shou ld at least reduce the need for pumping. --Chriswaterguy · talk 18:12, 12 January 2008 (PST)

No, I believe the air pump installed on this system only uses about 50 Watts. Here's a link to its specifications: Airtech 40. It's more than sufficiently aerating 700 gallons. GoodSignal 20:59, 12 January 2008 (PST)

Airtech40 Spec

Some Questions for cleaner water[edit source]

Great project here.

I have some questions. How do you initially seed the bacteria when starting a new cycle every season?

I just buy a bottle of Roebic Laboratories K-87 soap digester and split the bottle between the drums and reservoir. Look over the section, Beginning of season, one more time. --GoodSignal 08:52, 19 November 2008 (UTC)

Will adding some ceramic noodles such as the ones used in an aquariums help to sustain the bacterial colony?

I'm not familiar with the ceramic noodles you are referring too. Maybe you could provide a link or describe them further. If it's media designed to create more surface area for bacteria to adhere to, then I would recommend it. Otherwise, I would go with one of the types of media available for sale (a couple of links provided below). Providing surface area significantly increases the number of thriving beneficial bacteria, allowing for more efficient system. --GoodSignal 08:52, 19 November 2008 (UTC)
One method that I haven't tried yet, but would be thrilled if someone ventured to experiment with is: Using the plastic in your recycle bin as a bio-media. I would cut of the bottoms of a bunch of plastic bottles and stuff all the pieces in a few mesh bags -- like the ones that onions and potatoes come in when you buy them in larger quantities. Then hang the mesh bags full of plastic cuttings in the drums (maybe not the first drum though). Cutting the bottoms off the bottles is essential because we don't want to create any water pockets where oxygen from the aeration can't flow freely -- any pockets that aren't sufficiently aerated have the risk of becoming an anaerobic environment. Using the mesh bags makes periodic cleanings so much easier -- just hoist the bags out, spray them down, clean out the drums, then drop the bags back in when finished. I would like to see this work because all the material is free, and most of us have access to a relatively endless supply of empty plastic bottles. --GoodSignal 08:52, 19 November 2008 (UTC)
If you have some money and want to go with a product designed for this purpose, consider the following products:

With just aeration for the bacteria to feed on, will this be enough to produce a non hazardous water for flushing toilets?

I believe that depends on the biological oxygen demand (BOD) of the reclaimed water coming out of the system. If the BOD is low (I'm sorry I can't tell you how low it should be) then I think it would be a great use for the reclaimed water. But if the BOD levels are high, then you risk creating an anaerobic environment because water sitting in the toilet's tank and bowl is stagnant between flushes. An anaerobic aquatic environment will introduce very unpleasant odors. --GoodSignal 08:52, 19 November 2008 (UTC)

When it comes directly from the reservoir If I add a UV sterilizer, similar to the aquariums to the water exiting the last drum and before being stored. Will this help to kill any remaining hazardous bacteria?

Very likely. The effluent from the system I built is, optically, very clear; So, I think UV treatment would be effective at sterilizing the water. However, keep in mind that whatever dead bacteria that are left in the water are essentially nutrients that new bacteria (if introduced) would likely feed on. A COD (chemical oxygen demand) test would give an idea about how much nutrient is present.
I'm sure any manufacturer of these UV treatment systems would be glad to give you vast quantities of literature to tell you all about it. --GoodSignal 08:52, 19 November 2008 (UTC)

Thanks for all the details.


Is chloritnated tap water a concern?[edit source]

Thank you for your feedback.

The ceramic noodles I mentioned are the same as Bio-glass filter media. However, I think I will use many cut pieces of pvc piping glued together to form a mesh, since the amount of the bio-glass media required for 3 large barrels would make it too expensive.

With several layers of this pvc mesh, it should create enough surface area without creating any anaerobic pockets since the water and air bubble can freely rise from the bottom to the surface while passing through the mesh. Also, these layers could be easily removed for cleaning and re-inserted.

That sounds great! Please take photos and document your pvc mesh creation (along with the rest of your system) and post it on appropedia. I would certainly like to see the mesh, along with the rest of your project; and I know others would benefit too. --GoodSignal 15:25, 20 November 2008 (UTC)

I was also thinking of using one of these automatic aquarium feeders, filled with powdered benign bacteria (not fish food), to top up the bacteria automatically on a weekly basis. This should ensure that the bacteria colony is thriving.

The only times I have had to reseed the beneficial bacteria was after system cleanings and after heavy duty cleaners were used and rinsed down the drain without remembering to switch the drains to the septic lines first.
Using an automatic feeder would certainly ensure that the beneficial bacteria is present. I don't discourage it at all. I have found however, that as long as the environment is favorable for the beneficial bacteria (aeration, nutrient rich water, and surface area), they tend to stick around and thrive. Re-seeding only seems necessary occasionally. Additionally, bacterial cultures tend to specialize to their particular environment. I wouldn't doubt that specialization happens in these gray water reclamation systems too -- even specialization from drum to drum within the same system as the nutrient levels and particulate matter change along the way. To encourage this specialization, I would even suggest pulling a court or two of water from the drums prior to system cleaning, then reintroduce them after the cleaning is finished. --GoodSignal 15:25, 20 November 2008 (UTC)

My last concern is, since the tap water we use is slightly chlorinated by the water company, do you think this will have an negative effect on the bacteria colonies? The water supply for the shower and sinks which will be my main source of Greywater is stored in a classic roof tank, so I guess the chlorine would have degraded by then. What do you think?

I don't think you have anything to worry about regarding tap water chlorination. Even if you didn't have the roof tank (where the chlorine has a chance to off-gas), there is so much aeration in this system that any residual chlorine would quickly dissipate to the atmosphere. --GoodSignal 15:25, 20 November 2008 (UTC)

Thanks once again.

Keep up the good work.

Rgs Etienne

UPDATE[edit source]

You may find some initial details of the project over here:

The site will be updated when I have some more free time.

Rgs Etienne

Question about the barrel[edit source]

A question was asked about the barrel here: User talk:Triwalla. The user hasn't registered their email (no "E-mail this user" link) so I don't know that they'll see an answer, though. --Chriswaterguy 10:13, 20 March 2012 (PDT)

I got the barrels for the Occidental_Greywater system from a local cannery. I think the particular barrels I used originally contained vinegar. The barrels are a waste product for the cannery, but there is enough reuse demand that they usually sell them. GoodSignal 19:48, 30 March 2012 (PDT)

Additional Questions[edit source]

Asked on 2015-06-09
1) Why did you choose the system you have now?
2) Did you do any experimenting with a sand/charcoal filtration system. Would you consider adding this in addition to your current system?
3) Would adding or subtracting barrels/chambers to the system improve/or hinder the system? How did you decided to use 4 barrels? I have seen several other systems with less.
4) Does the system emit any odors?

1) I chose this system based on the two major criteria points. Water storage was necessary and it had to be very easy to maintain.
2) There are several reasons that I wouldn't use a sand/charcoal filter.

  • Charcoal is out of the question because its purposes is for removing chlorine and Volatile Organic Compounds, which is generally done for drinking water. Converting greywater to drinking water without a government certified facility is illegal, and for good reason. And since we're just watering decorative plants, that would be an unnecessary expense.
  • Sand filters are messy and require frequent cleaning. Cleaning sand can be a significant maintenance issue.
  • Cleaning generally requires clean water for back flushing which is can be expensive when water is in short supply.
  • Without frequent cleaning, it's liable to smell bad.
  • The bio-film that develops in sand filters only stay effective if there is a constant supply of water passing through. It can't dry up or the bio-film dies and has to be rebuilt. Household water use patterns are anything but constant.

3) Each additional barrel is progressively cleaner than the last. At a certain point however, the benefits diminish. Water coming out of the second barrel is still rather dirty. By the fourth barrel, the difference in clarity is remarkable. This system could probably get away with three barrels. My preference would be to add some form of easily cleanable biological media for the ecosystem to adhere to in the fourth barrel. I think this would have a greater affect than any additional barrels.
4) It smells mildly sweet. This is typical of a well aerated system. If it ever smells foul, that's a sure indication that pathogens are rampant and something needs to be fixed right away. Bad smell means the grey water has turned to black water. This can happen if the flora of beneficial bacteria gets compromised by excessive chemicals poured down the household drains that kill them off. The flora can be re-seeded with off the shelf products. Bad smells will definitely happen if there's not enough aeration. Good aeration is a key ingredient for the success of this system.
--GoodSignal (talk) 10:27, 9 June 2015 (PDT)

Short Link[edit source]

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