Dead leg water pipes.

[pontiff]

As mentioned in a previous thread I'm looking into using rainwater to supply downstairs toilet. When I disconnect the mains cold water supply to the cistern can I just blank it off or do I need to rip open a few walls to find out where it tees off from and stop it there?

I think the term is dead leg but as Manuel in Fawlty Towers would say... " I know notheeng!! 

Cheers

[Iain]

Hi
I have just blanked mine off with a Hep reusable blank. If I have any problems in the future I can just connect back up again. Or when my rainwater pipe froze!

Iain

[pontiff]

Hi Iain,
That's exactly my plan, just wondering if any stagnant water remaining in the pipe could cause issues. Probably reading too many scare stories on t'interweb again. I might find the tee off relatively easily anyway when I redo the cloakroom so prob worrying too much.
 

[odbob]

I suppose that the official answer is yes, you should look for the originating connection and blank off there so as to prevent a build up of contamination, but I and many others I have no doubt, take the easy option and leave a dead leg when this is the practical solution, after-all in life there are many dead legs.
There are however other options :-
1; make a note so that later on when you are destroying another part of the house, you can attend to this work retrospectively
2; consider that to have a mains connection close by is not necessarily a bad thing, why not add a double non return valve and isolator and utilise this as a standby in the event of no rain water.
Both the options above, I have used in my rain water system, it works for me

[pontiff]

I also thought about having two inlet valves into the cistern, one for the mains, one for the rain, this would give a 15cm physical gap so no possibility of contamination ( unless the overflow failed  ). I could use the old overflow as the second inlet (the new syphon has an internal overflow into the bowl). Then if the water failed I could just open a valve and use mains.

Sure that would contravene a reg or two tho. Just a thought . 

[odbob]

Yes, I concern myself with regs, many of them are of absolute need, but then there are those which are questionable, and this one of preventing back contamination is just one example. In the instance you have described, where it is imposible for the cystern water to rise sufficiently to contamate the mains water, I see no need of special precautions, that said, it is just my opinion and I have no intention of selling my house and so as long as I ensure that no contamination will affect me and the gaffer, and obviously that no contamination leaves my house, I am happy.

It is for each and everyone of us to be responsible for our own actions