Here’s our latest bit of technological fun. We have decided to try to engineer a rainwater recovery system into the house, despite our sedum roof, which will absorb a lot of the water unless we get heavy rain. The tank is oversized at 6,000 ltrs so that the reduced rainwater because of the sedum can be made up in period of heavy rain.
However, having made this bold decision we now find there are two issues we will have to contend with. Firstly running a bigger tank works against the principle that the tank should regularly rise and fall during wet and dry periods so that the water is regularly exchanged.
Secondly the fertilizer put on the sedum roof at installation could possibly wash into the tank, encouraging orgnic matter to bloom. This has been a problem on other installations so we will have to watch out for this. However our roof and the installation fertilizing was done some months ago so hopefully most of this has been adsorbed or washed through.
Certainly we are advised by the technical department of the tank suppliers not to use the system for the washing machine, only the toilets.
The tank and pump kit cost £2,600 (plus VAT) and the groundwork installation plus the additional “grey water” plumbing system in the house (with it’s own header tank) will probably double this cost. So another thing to play with but unless water prices soar over the next 10 years a doubtfull excercise in cost effectiveness.