Greywater Drywell

Drywell

I finished building my drywell last weekend with the help of my neighbor – the one with the earth moving equipment.  Two weeks earlier my oldest son (21) dug the 2′ deep by 17′ long trench for the drainage pipe.  The trench took him about eight hours to dig, with a fair number of texting breaks mixed in.  In all fairness to him though, the ground is pretty rocky around here, and it’s also kind of hard to dig while on your hands and knees under the cabin.  The drywell pit, on the other hand, only took my neighbor about 10 minutes to dig with his excavator.  I can’t even imagine trying to dig a hole that large by hand in this soil.

The drywell is strictly for disposal of the greywater generated in the kitchen and bathroom.  Since there’s no toilet in the cabin, I don’t have to worry about any blackwater disposal.  The drywell itself is fairly simple, and I got the plans for it in the eHow article Make Your Own Gray Water Dry Well 55-Gallon Drum.  The entire drywell cost less than $150, which included all the materials and my neighbors time and equipment.

Wanting to do the right thing, I had originally contacted a local septic company last year to ask if they installed drywells for greywater.  They told me they couldn’t install a greywater system and that I would need to have a septic system.  It just so happens that septic systems around here are usually mound systems that run anywhere from 10-15K.  When I gagged at the price they said they could install a holding tank instead for 7.  When I asked if they meant $700, they corrected me and said $7,000.  For 7K I’d keep using a bucket under my sink for a long time.

Here’s some more pics of the drywell construction.

28 thoughts on “Greywater Drywell

    1. Steve Post author

      I’ve read that exact link before, but I doubt it would ever get approved by the county. I’ve bent the rules on a lot of things in building my cabin, but installing an illegal septic system for blackwater is something I would never do. This is all a moot point anyway as I have a great outhouse that works in all weather conditions with no winterizing/dewinterizing necessary.

      Reply
      1. jbmckim

        Oh, of course. Jurisdictions are everything. It’s a bit more restrictive now but when my inlaws built a cabin in Wyo about 25 yrs ago, they had one inspection…for septic percolation. That was purely to determine the leach field size. It was one guy with a bucket of water, a hole and a stopwatch.

        Just found your site and I have to say I think you’ve found about the perfect tight rope between the various competing requirements.

        Reply
  1. Brandy

    I live near you and am thinking of a similar project. I’m thinking I may work in modules to make it more affordable. Build on container then add on down the road. What do you think? How hard do you think it is to add on to these?

    Reply
    1. Steve Post author

      Brandy:

      I personally would not consider building piece by piece with containers. One problem would be when adding a new container, you would then need to cut the adjoining walls out. This would also entail removing the stud walls in addition to the spray foam insulation. I definitely wouldn’t want to use a cutting torch anywhere near spray foam insulation. With containers I feel it’s best to do it all at once.

      Steve

      Reply
    2. Old MSgt

      Modular construction is quite possible with pre-planning. Study industrial and military ISO container websites. such as the Sea Box site. You either need to learn basic welding or hire a welder. I suggest learning to weld as that’ a hugely useful skill and you can buy good equipment reasonably. You don’t need to use a torch to cut the sheet metal. Sawzalls are loud (solved by wearing ear plugs) and get the job done. With the project being a work in progress you could use removable insulation on the outer wall you plan to modify. You could, for example, do a “two ISO” open floor plan in the manner shown on this site, then leave some outer walls intact and cut lesser sections out to join your “additions”.

      I have two 40-foot High Cubes (if at all possible get the 9’6″ high High Cube ISOs, you’ll greatly enjoy the headroom) I’ve welded to a couple of long I-beams (make friends with a scrap metal dealer or similar) and I’ll be framing the internal wall sections I remove with square tubing. The roof joint can be spanned by ordering two 20-foot nominal lengths of 2″ wide x 1/8″ thick steel. I’ll MIG weld all the way down the joint using E71T flux core wire. I’m using a “suitcase feeder” run off a DC welder. You can rent gasoline-driven welders etc from local welding supply companies, or if you want an outstanding generator with better parts support than most genset companies, order a Miller welder/generator. BTW Great Stuff black “Pond and Stone” foam survives outdoors and is what I use in preference to yellow. Hang out on welding forums such as weldingweb.com and you can read tips from pros who mod ISOs for a living.

      Also note that steel building companies offer roofs and buildings designed to incorporate ISO containers so you can have many choices for your space, such as ISO “wings” with an open and tall center area. Steelmaster and American Steel Buildings etc have kits which are easy to erect. (Use anti-seize on the bolts in case you decide to change some out to hang items from the roof.)

      Reply
      1. Steve Post author

        The one thing I will have to strongly disagree with you on is in using removable insulation on an outer wall. Closed cell spray foam is the ONLY insulation I will recommend at this time. Any other type of batt, loose fill, or panel insulation will eventually allow moisture laden air to reach the outer walls and condense. And while it’s possible to add on to any type of building, why go through the hassle when you should just plan ahead properly and avoid the headaches.

        BTW, I originally looked into the SteelMaster container cover system for my cabin, but the cost was almost an order of magnitude higher than my DIY wood frame and steel panel roof.

        Reply
  2. ken

    Is 2 feet deep enough for your drain pipe? I am in NH and I would think it would need to be 4 feet down to be below the frost line. Have you had any trouble with anything freezing? thanks.

    Reply
    1. Steve Post author

      Ken:

      Since these are only drain lines, have an adequate slope of 1/4″ per foot, and are >18″ underground, they really shouldn’t freeze. I was also worried about this when I built it, but everything I read said it wouldn’t be a problem. On the other hand, if these were supply lines, they would freeze.

      Steve

      Reply
      1. Sarah

        Am also looking to build grey water system on tiny house in NH, curious if you found predictions as far as freezing correct? How has the system worked out for you overall? Did you ever run into problems with permitting? So little cold climate information on grey water, would love to hear about your experiences.

        Reply
        1. Steve Post author

          Sarah:

          I have not had my system freeze up, but I also don’t run a lot of water through it in the winter. The most I have run through it in a weekend visit in the winter is about 10 gallons or so into the sink. The coldest it ever got on a visit was -10F at night, and I didn’t have any problems. Since everything is underground it’s kind of hard to know what’s really going on in the pipes and drywell.

          Steve

          Reply
  3. Sandy

    Trail cameras can be bought at the “W” mart for about $50. My first one was tampered with and rendered useless. Now I have two more that work very well. They are aimed to watch each other as well as the area of interest. Any one nearing one is captured by the other.

    Reply
  4. Bob Rogers

    Hi. Don’t know if you’re still following comments on this post. I’m looking into creating a similar system. Can you tell me how yours has been holding up, a couple years in? Also, what about stuff like grease, food bits, etc. that get washed down the sink? And soap and what-not from the shower? How are those dealt with? Thanks for the thorough write up and good pics.

    Reply
    1. Steve Post author

      Hi Bob:

      It seems to be holding up just fine, but there’s been very little strain on it so far. I don’t use a lot of water when I’m at the cabin, and what’s used is pretty clean. I’m also careful to keep the sink drain strainer in place to keep food particles out. From what I’ve read, one of the worst things to go into the system is grease, and I try to drain any that I generate into the garbage rather than have it go down the drain.

      I know that there is a finite lifespan for my drywell, just as there would be for a septic system. If I can get even 10 years use out of it, which I’m pretty sure I will, it will be well worth the $150 I spent on it. Definitely much better than 10-15K for a septic.

      Steve

      Reply
  5. Ryan

    I am constructing one of these for my kitchen sink and washer. I was wondering what the dimensions were for your hole? Also, roughly how many holes did you drill into your drum?

    Reply
    1. Steve Post author

      Ryan:

      I didn’t have a set size for the hole, but my best guess is that it was around 6ft x 6ft. As for holes there were probably 16 one inch holes or so. Just make sure the holes are sized appropriately so the gravel doesn’t pour into them.

      Steve

      Reply
  6. TIna

    Hi Steve, I have read many of your ‘tin can cabin’ posts over the last several years learning as much as I could about building a diy container house which has been a big help, as my family were building a shipping container house in Australia. The containers were prefabbed at home on our farm for 12 months and then relocated 3 hours drive away to be a vacation house.
    We rebuilt the prefabbed containers on stumps and then added roofing iron, wall cladding, verandah etc and the work continues…
    I have made a website which is not quite finished but there is plenty to see, this maybe quite different to what you have seen before, I have found it amazing that every diy shipping container house is different and love discovering new and different designs.

    Reply
    1. Steve Post author

      Hi Tina:

      Love your house, and especially your property by a river in Australia. Your country is definitely on my bucket list for a visit when I retire. I also like your 360 degree wraparound porch – probably a requirement in your climate.

      Thanks for sharing.

      Steve

      Reply
    1. Steve Post author

      Jeff:

      Yes, the blue barrel is empty and it has not caved in. Keep in mind that full 55 gallon plastic drums can safely be stacked three high. This means that a single drum can withstand having greater than 900 pounds stacked on top of it. The amount of dirt covering my drum is nowhere near that, so I feel pretty confident that it will hold up. I would however not recommend driving over it with heavy equipment.

      Steve

      Reply
  7. Stephanie

    We have had a pipe in the ground for th last year but have been trying to come up with the simplest finished system. I like this design and wonder if just making a top hatch for periodic clean out would make this system last longer. It’s just my husband and I in our tiny home. Showers are taken together, HE washer and the sink would be the only contributors.

    Reply
    1. Steve Post author

      Stephanie:

      Having a method clean out the system seems like it would be a good idea for you. I feel that my system gets so little use, that by the time it needs to be cleaned out I’ll just dig it up and start over again. And if I’m really lucky, it’ll last just long enough that it’ll be my kids problem. :)

      Steve

      Reply
  8. Alleah

    Hi Steve,

    Wow great content and cheers for keeping up on the comments! Amazing!

    I’m thinking of putting a few campsites on some property and like this system but am curious at how much water usage 55 gallons could handle.

    Do you have any guess on how long it takes to drain? It looks like an average 8 minute shower uses about 17 gallons. So in theory the tank could only hold a few showers before filling. I know you have light usage, but perhaps you have some idea?

    Best,
    Alleah

    Reply
    1. Steve Post author

      Alleah,

      So much depends on how permeable your soil is, the makeup of the wastewater, and how much water you plan on running through it, that there is no easy answer. The only reason that this works so well for me is that I rarely go through more than 20 gallons in an entire weekend, and it’s usually more like 10 gallons. There is also very little in the way of organic compounds in my wastewater that would cause it to clog up the soil.

      Steve

      Reply
  9. Andrew

    Hi,

    Loved reading through your insights – we are currently planning out an off-grid container house in a very rural location – in a developing country at that – where town utilities don’t exist. However the upside being that council regulations and the like don’t exist either.

    Would your system still work if I were to scale the size up, as long as the ratio between drum volume and hole volume remained constant? Looking at something to handle a 1000L tank or thereabouts.

    PS. Has anyone tried using incinerating toilets as an alternative to blackwater systems? If anyone has used those, please share?

    Cheers,
    Andrew.

    Reply
    1. Steve Post author

      Andrew,

      You are dealing with a size (1000L) I have no experience with. I would recommend contacting a qualified wastewater professional for this type of advice. In regards to an incinerating toilet, I have known people that use them and like them. The biggest issue with them is the amount of either electricity or propane that they require. I would recommend looking at composting toilets as they are much less expensive both in initial and operating costs.

      Steve

      Reply
  10. Jeff

    How do you size your grey water system? How big of a barrel is needed for lets say, up to 8 people but mostly 3-4 people. Summer & winter use about every 3 to 4 weeks. We stay up to a week at a time. Shower, kitchen sink & bathroom sink.

    Thanks
    Jeff

    Reply
    1. Steve Post author

      Jeff:

      I didn’t really give much thought to the size when I built my drywell since the cost was so low ($150), and I knew I wouldn’t be taxing it with very much water (about 10 gallons per weekend visit). If I did need to size it, for let’s say a full-time residence, I would take into consideration the number of people, estimated water usage per day, high flow events like showering and clothes washing, and absorption rate of the soil. The last consideration, absorption rate of the soil, is critical in how fast the drywell will lose its water. A higher absorption rate would allow for a smaller drywell while a lower rate would require a larger one. The absorption rate can be determined through a percolation test which isn’t too hard to do.

      My system also has a bypass in case the drywell would ever fill up – which I can’t ever imagine happening. Underneath my cabin I included a screened Wye fitting (angled upward) to the drain line that would discharge excess water under the cabin in a worst case scenario, instead of backing up into the cabin. The Wye fitting was mainly added to equalize pressure in the drain lines since I have waterless traps with elastomer seals that could be damaged by a pressure buildup in the drywell from bacterial action.

      Hope this helps.

      Steve

      Reply

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