Rainwater Storage and Reuse

One potential problem is achieving the correct minimum pressure and flow rate that washing machines need. Then there's the problem of the plumbing work needed to feeding the rainwater to the washing machine, toilet etc, in place of the rising-main pipework that is already there.

"grey water" is the keyword, but you may have to learn German as they are the ones for 3 water systems inside houses.

Interesting thought occurs: what's the ratio of water falling on roof to water consumption? For my little house, about 40 m^2 (horizontally-projected) area and average annual rainfall of 0.7 m, gives annual of 28 m^3. I use about 64 m^3 a year but could easily halve that. A lot closer than I'd expected. In a wetter area with a bigger house and some economy...

nib

Grey water storage systems and reuse were all the rage 10/20 ? years ago, now they hardly get mentioned. ISTR the big problem is odours from the stored water , is this the case or are there are other reasons why they have fallen out of fashion ?

You may also want to check out the legalities. Water companies will view it as stealing their water.

I am sure there is a lot more to worry about than the odd whiff.

The tiresome emergence of Legionaires disease springs to mind.

Yes, will do, don't want to steal from the fine upstanding and law abiding water cos.

Many examples exist - including new build.

Yep - bird poo and worse. That's why I asked . . .

I take the point. But I remember being warned off ages agoi when I was musing such an idea. From memory, they (legally) get to charge you more for your waste water processing as they will presume/assume that you are putting more down the drain than you are taking from their mains.

Remember the only reason they don't charge you for the air you breathe is nobody has yet devised how to make the poor pay the most for it.

Yes - I've been round some housing projects in Germany with that sort of setup. Just wondering how/if it works in the UK.

Citizen Bob strikes again!

I process my own waste and get 50% off water bill

I'm using about 30m3/year. Not done any calculations but guess 40m2 of guttered roof would cover the toilet at least (so to speak). Judging by the rate a 100l water butt fills from a small offshot . . .

Our bill is so low that any work to reduce it will never pay off.

Now balcony solar on the other hand :)

And whatever else is in the guano on the roof. Would UV sterilization be practical?

Dunno. But home grown solar seems an ideal way to power equipment to pump and sterilise ....

What is the rainfall in your area? Here in SE Essex we go weeks/months without enough rain to fill a single water butt from half of the roof.

How clean is your roof. I find that I have around an inch of thick sludge/mud in the bottom of my water butt per/year. Consider how dirty a car cn get after certain rain periods. The same dirt will be in the water you collect. Make sure the system you install is easy to clean out and make sure that the outlet from the tank is well above any sludge level.

If you tank is outside make sure that it is sealed or you may find that mosquitoes will find that it's an ideal breading ground.

About 10 years ago I viewed a house on a new build estate. The first phase had used rainwater harvesting and the second phase hadn't. The developer said keeping the system working turned out to be unreliable - something about problems with filters. (it may also have been that the got planning permission based on the sustainability claims of the first phase and then walked them back later... wouldn't be the first time)

I think it could work in a building like an office block or a school where you have a predictable water demand and space for large holding tanks, like those digester tanks on farms, and plantrooms with maintenance staff. For a single family home it doesn't seem worth the effort maintaining the filtering equipment.

OTOH, if you're off the water mains then that tips the balance somewhat.

Theo

Like you - fits and starts. But the storage doesn't 'run dry' (of course) - when it gets too low it's topped up from the mains. Like a toilet cistern.

I'd think a 200L tank would last about a week. 200L is small but might overcome a number of potential problems by having a decent turnover. I'd guess that most of the time it'd be full - guess based on a 100l water butt in the garden fed from a small roof.

Well, it's a new roof - but that's not the thing. It does after all get washed every time it rains. The water butt is fed from a cleanish roof but still lends up with (like you) a good couple of inches of mud in the bottom. That's why I asked about filters.

In my case a cellar. So rarely if ever above 15C. Mostly 8-12C. Too cold for mosquitos but maybe ideal for something else - hence the question.