High watertable and clay soil

Greetings fellow permies!
We want to install a kitchen and bathroom in our barn.  The bathroom could see regular use for upto four people living in a finished apartment, potentially. We need an inexpensive greywater and blackwater treatment plan.  I've tried to research options but I'm having a hard time finding systems that can be designed to work for our particular situation of a high watertable and clay soil.  We live in a rural area outside of Seattle with an average rainfall of 24 inches.  Currently we do not have a rainwater collection system but, plan to install a cistern.
What I seem to understand about household water recycling in general is:
1. Laundry, shower, tub, and dishwasher(?) should be pretty easy by piping into an underground trench layered with gravel, (sand?), soil, wood chips and plants.
2. Kitchen and bathroom sinks are tricky due to higher contaminants and grease.  I'm not sure what the best system is for greywater coming from these, again especially considering our rainfall, watertable and clay soil.
3. Toilet blackwater needs a multi-chamber approach with an anaerobic component.  I think we're going to take the "easy" way out and get a composting toilet.  Either and incinerator type or perhaps a homebiogas. Incinerator is easiest for us as our year round temps aren't high enough to reliably run the system year round. We might consider putting the system in a greenhouse or heated space as a solution.

So, my big question is greywater treatment feasible with our circumstances?  I don't want the expense of a traditional septic system, I'm hoping for a well built, long lasting, diy option.

Please lend me your expertise, experience, and resources!

Tangentially, as a separate project, our home has a traditional 4 bedroom septic system and we are a family of 6.  If we divert greywater from the shower, tub and washer will that cause a problem in our septic system?  If I understand correctly the septic system needs enough water to function properly so, I'm worried about diverting too much water away from it.

Thank you for reading and replying!

There are a few questions that need to be asked.
- Are you in a low spot?
- How far to a watercourse or a drain which goes to a watercourse?
- are neighbours close?
-Have you tested the soil to see how absorbent it is?
- If the soil is not absorptive, where will the greywater go?
Some statements
I don't want the expense of a traditional septic system, I'm hoping for a well built, long lasting, diy option.
- I dont think this is possible foe 4 people
- You will need a grease trap for the kitchen waste water

For the black water/grey water solution consider having a pump-able tank if you cannot add to your septic system.

Ann said,  Toilet blackwater needs a multi-chamber approach with an anaerobic component.  

What are you state/country rules?  They probably will accept a pump-able tank otherwise a septic system.

Ann Baker wrote:

Tangentially, as a separate project, our home has a traditional 4 bedroom septic system and we are a family of 6.  If we divert greywater from the shower, tub and washer will that cause a problem in our septic system?  If I understand correctly the septic system needs enough water to function properly so, I'm worried about diverting too much water away from it.

Thank you for reading and replying!

We are a family of 8 and our toilet was the only thing connected to the septic and it was fine because we’re home all day long and even though we limited how often we flushed, it was often enough to have enough water in the system.

That said, our greywater system was condemned. Even though we use less water than the average 4 person family, it was still too much water to be absorbed by our clay soil with high water table (except in seasons of drought our ground is always soggy)  and would spill into our neighbor’s land. We didn’t really have the resources at the time to plant enough to reroute the water and public health stepped in and told us we needed to fix it immediately.

What ended up being approved by the powers that be was rerouting our old septic and the greywater into a Fuji Wastewater Treatment System and draining into an already swampy low lying area on our property.

I don't want to dissuade you, but a DIY option in King County will be a real trick.  The project is possible, but doing it legally and without heavy fines is not.  Any septic grey or otherwise will require a licensed engineer's plan submitted and approved.  If your are anywhere near what is regulated as a wet land, much of the foot hills on the eastern Cascades, it is a hard "no".  There are entire government agencies chartered to protect watershed in Snohomish and King counties.  If it is not a  "cookie cutter" solution that fits their paradigm, I doubt they will even listen much less consider.  Contaminate a wet land area and they will bankrupt you.  Please proceed with caution.  

We had exactly the same problem as you Ann.  After much research, our solution was to build a reed bed.  Our grey water is harvested off to an underground pipe system to keep the lawns green and the black water goes through the reed bed.  At the end, the local wildlife and our cats drink from it.  The reedbed outflow is into a large sump which is surrounded by water slurping trees (in our case, river sheoaks).
I think that this may be a useful site. https://www.waterandwastewater.com/reed-beds-in-wastewater-treatment-sustainable-purification-methods/

In my area, reed beds and cattail beds are used for grey water, but climate is as important as soil. We are sooo... wet in the winter, when the sun is low so the plants are largely dormant. My acquaintance who used that system summer and fall, shut it off and used the Municipal sewer system for the winter.

I do know there's been some major shift in leach field concepts in my region. They are using much more sand as the bottom layer in the trenches and done actual testing in real-life systems to confirm the new systems are working as predicted and not still allowing nasty stuff to permeate down to the water table.

From your description, you may have to start "above natural ground level" using raised beds (my acquaintance's system was small, so he upcycled 3 bath tubs for the purpose.)

I would do all the research into successful systems that you can, and be very aware of Jack Edmondson's concern above. You can pitch a "better system", but ultimately, you may need to convince others that this can be done safely and responsibly, and hope they will give it a try. Change is scary for petty much everyone - understanding and patience are key.

Jack, after reading your reply, I realized that you are 100% right in dissuading me.  King county would absolutely sue my pants off! I can get rather dreamy about sustainability and forget all about some very important matters pertaining to my daydreams.
So, perhaps someone can give me advice as to how big of a tank I would need if we were to route everything from the barn remodel which would include a kitchen and bathroom minus the toilet with regular use for a family of four and we'd also like a separate occasional use bare-bones kitchen for large gatherings.

A farm near us had an above ground holding tank that their farm store with full bathroom and wet bar went into and they would just have it pumped. But,  I have no idea how big a holding tank would be reasonable for our plans or how often I should expect to have it pumped.

Thanks for any input!

I have had a look at the Kings County Codes.  From my reading it seems to be that for rural areas, if there is no contamminant leakage, it is prety much OK to have a reed bed.  There are commercial plans available which contain the appropriate certifications.  I did not see anything in the codes which would raise a red flag.  We have had a lot of success by asking for help from the rule enforcers
- "I need to do XYZ and need somewhere to start.  What do you suggest?"

We used this approach for our house and have now done the same thing for our local Men's Shed.  Our local council has signed off on worm septic which produces worm castings,  worm wee, and pure water.  which can go into watering trees.  If you ask, the worst thing they can say is "No" - then you can ask what is their ideal solution.

Biogas generators can use a low temperature bacteria to get you over the winter.  Some in ground based units have a small heater using graphine which from my experience is quite robust.  Micropowergrids is my go to site for all things off grid and alternative. https://www.micropowergrids.com.au/_Bio-Gas/Punix1_Residential.html

  There is a 100% catchment and the outflow can be measured for potential polutants.
Hope this helps.  Good luck with your endeavours.

Paul Fookes! Amazing!
How much did your system cost?

Ann Baker wrote:Paul Fookes! Amazing!
How much did your system cost?

We have not installed this system.  We have a reed bed system which I built from scratch. ( see post above)
We purchased two dual axis solar trackers from Denis.  Some of our earthworks are shown in the installation section of the site.

This is an example and could provide a solution without risking polluting the surrounding area. I have not checked if there are local to you suppliers. I think that Denis ships world wide.
Best wishes.