Replumbing cold water supply to use rising main

[markp]

Hi
The house we moved to last year has the rising main feeding a cold water tank in the loft. The loft tank has 1 feed for upstairs cold taps and 1 feed from the same tank for the downstairs cold taps. I am not happy about the cold drinking water coming from the tank instead of the rising main so am changing the setup. The airing cupboard contains the rising main and pipework back down from the loft to the cold supply downstairs. I have teed off the rising main in the airing cupboard just before it goes into the loft space so I can then direct this pipe back downstairs to the cold supply pipework (I can't branch off the rising main near to the downstairs taps without a lot of mess). I have an isolator on the new branch and have tested the water quality from there before connecting back to the cold water pipework. The water from this new feed is quite yellow and actually much more discoloured then the current feed from the loft tank. I have also compared it to a sample from the outside tap which is the only other branch off the rising main, and this is the clearest water, which I expected should be the same as the new branch I have made.

So my questions - if the outside tap water from the rising main is perfectly clear, is it possible in the 6m of pipework I have teed off from for it to discolour the water this much? If so, then what is the best way to clean the pipes, or is it some other problem?

For info: rising main 15mm copper into loft tank, loft tank both feeds 22mm copper reducing to 15mm for cold taps, my tee off is pushfit with plastic 15mm pipe and isolators.

Cheers
Mark

 

[mikegas]

just run the water off for a minute it should clear

 

[markp]

Thanks for the reply. I have had it running for 5 minutes into the bath and it is still just as yellow

 

[PlumbBobBob]

is it possible that you have a bit of iron pipe somewhere on your system?

 

[GasmanxxxR1]

I imagine it is the mains pressure water blasting the scale and muck off the old gravity pipe, it shouldclear after a while

 

[Guest123]

Run the taps until it clears, can take a while though. This sounds like the type of scale from an old hot water system, are you sure you've not accidentally teed into something other than the cold feed?

 

[PlumbBobBob]

that's a thought, could be heating system water (worst case scenario)

 

[markp]

Good suggestions - it's definitely the rising main I have teed off from, turned off the supply at the main stopcock to verify flow and also traced pipework to cold water cistern in loft.

Before I teed off the rising main used to go straight into the loft cistern so I would have though the dirty water would also have been in there which in turn would then come back down to the taps. Actually that's a good point, the system is old and there are actually 2 cold cisterns in the loft as well as the feed and expansion tank. The rising main feeds tank 1 and then tank 1 feeds tank 2 (tank 1 also feeds HWC and shower) which is where the cold water supplies for upstairs and downstairs feed from (tank 2). I wonder whether the sediment has always been in tank 1 but never transferred to tank 2 which is why the tank 2 cold feed to the taps has meant the water is clear.

I wonder whether the pipe between the stopcock and the new tee off I have made is actually quite dirty inside and needs cleaning. I guess the reason the hose pipe feed is so clean (branched off rising main) is because it is so early on in the run of pipework.

Do you think just running the system through for longer than 5 minutes will clear the pipes or will I need to do something else?

 

[Guest123]

I'd run it for a while until it shows signs of clearing. May take a good few hours.