Ann Baker

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

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!

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!