Designing a filter for grey water.

[solar_cambridge]

Specifically only grey water from the washing machine as Im not interested in kitchen sink/dishwasher or shower. At over 65litres for a wash thats a lot of wasted water that could be used for toilet flushing or washing the car.
Now I am building my own filter setup for rainwater as I don't want to lay out over £100 for an inline filter. I'll be documenting that in a seperate thread.

I have found some very cheap stainless filter off ebay. Just passing the outlet from the washing over this has filtered a lot of fluff from a single wash.
This sort of thing http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=270701820972&ssPageName=STRK:MEWNX:IT Incidently thats proved very good for filtering rainwater as its caught a lot of grit in a single rainstorm yesterday

Now I see several websites sell 'grey water filters' which looking nothing more than some 110mm soil pipe. What Im thinking is a to use the filter in such a way that when its choked up with fluff(if I havent cleaned it), the water passes direct to the drain.  I have a couple of small water cisterns from old heating systems and lots of soil pipe and fittings. Just at the stage of wondering how to bodge something that works reliably and can be easily cleaned.

[tz0c0s]

You could use a large cistern (65L+) lined with sand, etc & a large bore overflow to waste in case of blockage.

H.T.H. Andy

[solar_cambridge]

You could use a large cistern (65L+) lined with sand, etc & a large bore overflow to waste in case of blockage.

H.T.H. Andy

Andy, I'm not sure how that would work and wouldn't I get sand flushed through into the storage tank? Do you mean pass the grey water through the filter with gravity to a lower storage tank?  I haven't given it much more thought as I've been rushing to connect up my two IBC's and up to the toilet in anticipation of heavy rain tonight and tomorrow. Rainwater is fed over the first stainless filter into IBC1. I've connected the lower outlets of the IBCs. Toilet is fed via a negative head pump which is sourced from floating inlet IBC2. So tank 2 should be pretty much clean water as any sediment should settle in the first tank.

[EccentricAnomaly]

http://en.wikipedia.org/wiki/Slow_sand_filter
http://www.ecohouseagent.com/hockerton-housing-project.html#image6

Also discussed in the The Water Book by Judith Thornton from CAT.

Two key points:

1) Sand doesn't come out the bottom because you have a layer of gravel with a layer of geotextile on top of it.

2) The sand doesn't just act as a particle filter. A fine mat of micro-organisms forms in the top few cm of the sand which eat nasties in the water on the way in.

[tz0c0s]

Hi Again,
  Some good links there. Yes, use any method you have to take the water, ex the washing machine into the cistern. I chose 65+L as the minimum cistern size as you say this is how much goes through the washing machine in one cycle. The grey water then passes through the home brew (but widely used) filter via gravity, in its own sweet time. Even if things are slow, you should not lose any. A large bore overflow 32mm+ to your houses drainage system should keep you from having any less than happy moments.

I would attempt to use the ex washing machine water as quickly as possible, not letting it hang around for extended periods, especially in summer. I would also keep both systems as cool & dark as possible.

I would not be making the sand bed 1M deep for your use. Slow sand filtration when used commercially is aiming to eventually supply the water to you & I.
I would make it a sensible depth & do some trials. The Hockerton people seem confident enough to bath in it, I wager there are more stages
I am unsure of the relative height of the washing machine in relation to the proposed filter or IBC but gravity would keep things cheep & reliable.

Have fun. Andy