Conventional Leachfield OK for Greywater?

Subject: Greywater in a conventional leachfield
Date: Thu, 13 Jul 2000
From: Art Ludwig <Oasis Design>
To: "Gene A. Johnson" <gene.johnson©>

[Gene Johnson of Livermore Colorado writes about using greywater in
a conventional leachfield. The environment is very dry Rocky Mountain
foothills, 15" annual rainfall (including snowpack water content),
elevation of 7500 ft. The soil perk rate is high (above 40 in./hour).]
> Goals: I live in a mountain subdivision. Due to high cost of installing a well
> ($15,000-$25,000) and close location to a community well, we installed a
> cistern system and haul water for our house. One goal was to minimize the
> amount of water I'd have to haul (family of four) and look at low environmental
> impact on our 3 1/2 acres. We have a spring we didn't want to over pollute. A third,
> but yet to be implemented was the possibility of subsurface irrigation for landscaping.
> We are not allowed to use well water for outside use due to Colorado water law.
> Background: I used both your greywater books to design my system and get health
> department approval (1996-1997). To lower my water consumption we did the
> following: Installed a Clivus M2 composter in the basement with a sealand low flush
> toilet in the second floor bathroom. We use a front load washing machine and picked
> a GE dishwasher with low water use features. I have separate greywater plumbing as
> the toilet goes straight to the composter. The greywater goes through a clivus greywater
> filter with sock filters and then straight to a standard leach field with infiltrators. My
> leach field is sized per my health department criteria. They require 100 gallon per person
> per day, but allow 25% reduction in size. SO I have a standard field to handle 4 people
> (100 gallons X 4 X 75% = 300 gallon per day capacity). Since I use a cistern, I'm required
> to have a water meter so the % of water shares I use can be monitored by the water
> district. I have used 106,000 gallons since building and occupying in November 1997.
> That's 108 gallons/day total or 27 gallons per person/day, 1/3 of the design capacity.
> In use the system is pretty transparent. We do keep the tap from running, etc., but
> overall it feel like a "normal" house.
> We do a lot of clothes washing, likely our biggest water use. With two kids and one of
> them a teenager there's always a pile of washing. Likely tied is shower/baths. I
> consciously take short showers and shallow baths but occasionally indulge. Everyone
> else ignores it and lingers. Problems I've had: Keeping up with cleaning the greywater
> filters. I'd like to modify and upgrade at some point. The washing machine tends to
> plug things up too fast. I should put a filter on the washer discharge to prefilter it.
> Sometimes I get behind with the Clivus and need to work the top layer some (yuk!).
> Sometimes I wish I'd installed the big Sunmar unit. I had a breach on my leach field.
> It sits on a mild slope. The excavator who backfilled it made the covering
> on the end too shallow and water found a way out. Boy does it get septic in there!
> Overall I'd do it again but with more knowledge and small changes.
> I've enjoyed your site, a lot of good input and info. I'm glad I avoided pumps etc, mine
> is all gravity. I still hesitate at reuse and plant xeriscape plants, but then our goal was
> not to use a septic tank since we used the composter. It was less costly to do it this
> way. I figure the system cost for composter/greywater was about $4000. That's about
> equal to having a basic septic system installed here.
> Do you know of long-term concerns of doing the greywater like I have? Any leach
> field issues?
> Thanks!
> Gene J.

Yes, you're likely to clog the leachfield someday. This problem could take years or
decades to develop, if indeed it ever does. The clivus sock probably doesn't get the
fine suspended solids out the way a septic tank does, and conventional leachfields are
designed to receive clarified septic effluent only, i.e. water with far lower suspended
solids. The more effective the filtration the longer it will take for the leachfield to clog.
This problem is described in Common greywater mistakes (see Error-Perforated
pipe for greywater distribution, Error-Blackwater designs used for greywater, and Error-
Reliance on government agencies for info on or construction of greywater systems)
and in the books. The local authorities have proven that they don't understand greywater
by permitting it the way they did.
In our latest edition of Create an Oasis we removed the "leachfield" design option. You'll
note that the older books which include it have cautions which describe the limitation of
the system, but we found these were widely disregarded and the design applied
inappropriately—sorry if this is what happened to you.
The fact the there was a breach in the leachfield suggests it may be on the way to failure;
the wastewater was apparently trapped in the lines under pressure, instead of seeping out
at zero pressure the way it is supposed to.
You could:
1) keep things the way they are and hope for the best, then abandon the current system
and do a different greywater system if you have to
2) proactively add a septic tank as a filter for the greywater while the leachfield is still
functional, to protect your investment in the leachfield, and/or
3) go to a different type of greywater system, especially for the laundry, as it is by far
the worst fixture for leachfields.
You mentioned getting tired of filter cleaning—I'm with you there. Options 2 and 3 could
get you out from under the filter cleaning. My favorite system these days is the branched
drain system; we just finished Branched drain greywater systems, which you might
consider getting in your research on option 3.

Sorry to not be the bearer of better news, & best of luck,

Full greywater how-to details from our store