Plumbing query

beyond the blue

beyond the blue

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Neil
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I've been fitting a new kitchen sink today and needed to turn the mains water off at the incoming mains stopcock and drain the cold water out of the pipes. We have a bathroom upstairs with a W/C, the W/C cistern has a 'quiet' cold water fill that fills the tank from the bottom ie. always below the level of the water in the cistern. When I drained the standing cold water from the pipes it started draining 'pink' water, so it was obviously syphoning water out of the W/C cistern that the wife puts these pink cleaning tablets in. Is this acceptable as these pipes have now been contaminated? I know that when the water has been turned back on the pressure would prevent it syphoning under normal use, but surely the W/C cistern filler should be fitted with a non return valve? What say you guys?
 
Time to call in a man who knows IMO.
 
Blame the missus, tell her the pink stinkers have corroded the pipes and get a plumber in.
 
beyond the blue said:
No non return valve? Failed non return valve? :thinking:
Click to expand...
all filling systems , work like a ball-cock, water comes in, fills system , water cannot go back on itself.
the water level drops, allows in water, until the desired level, until you pull the chain or otherwise then it starts all over again.
the only time that this would happen is on gate vales , when the pressure is greater on one side rather than other.
 
I take it there is a float valve of some sort to fill the W/C?

I can't see how water can get back into the system... weird.

Just run the water for a while to clear any residue- probably 5 minutes or so. You can test the water by having a cup of tea!
Any contaminant will make your tea taste off :)

In future, make sure the isolation valve (which should be fitted!) is turned off for the W/C.
It would probably be a good idea to get a non return valve fitted :)
 
mark richards said:
when you say that you need to empty the pipes, do you have a header tank in attic? because when you turn the water off it should stop instantly from mains, if you are getting coloured water it sounds like
its coming from a storage tank else- ware in house.
Click to expand...

No there's no header tank. The water that drains back after turning the stop cock off is just what is standing in the pipes going upstairs, but it is syphoning out of the WC cistern until that is empty as well. I wouldn't have known it was syphoning if it had it not been for the color of the last couple of litres.
 
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beyond the blue said:
No there's no header tank. The water that drains back after turning the stop cock off is just what is standing in the pipes going upstairs, but it is syphoning out of the WC cistern until that is empty as well. I wouldn't have known it was syphoning if it had it not been for the color of the last couple of litres.
Click to expand...
something wrong there mate, never heard of that before.
 
Siphoning is prevented by having an air gap... AFAIK there is no one-way check valve.
My guess is that the fill valve hose is positioned incorrectly/unsecured and is below the water line at max fill. This hose is not for filling the tank, it fills the bowl.
The other possible issue is that the water line/fill level is too high (filling the required air gap).
 
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sk66 said:
Siphoning is prevented by having an air gap... AFAIK there is no one-way check valve.
My guess is that the fill valve hose is positioned incorrectly/unsecured and is below the water line at max fill. This hose is not for filling the tank, it fills the bowl.
The other possible issue is that the water line/fill level is too high (filling the required air gap).
Click to expand...

The cistern is filled from below the water level by design "Quiet fill system" fills from the bottom up if you get my drift. That's why I think there should be a non return valve in there somewhere to prevent syphoning!
 
beyond the blue said:
The cistern is filled from below the water level by design "Quiet fill system" fills from the bottom up if you get my drift. That's why I think there should be a non return valve in there somewhere to prevent syphoning!
Click to expand...
Yes, but it still has an air gap... the basic design is like this.

Untitled-1.jpg

If the fill hose is in fluid it can siphon backwards, otherwise it can't. I don't know of any approved system that is entirely under water w/o an air gap (USA).

Edit: usually the supply inlet/outlet is an inner/outer tube design and it looks like a single stand tube.
 
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sk66 said:
Yes, but it still has an air gap... the basic design is like this.

View attachment 115865

If the fill hose is in fluid it can siphon backwards, otherwise it can't. I don't know of any approved system that is entirely under water w/o an air gap (USA).

Edit: usually the supply inlet/outlet is an inner/outer tube design and it looks like a single stand tube.
Click to expand...

Thanks Steven, I'll stick a photo of it up later, you might want to give me advice on the set up?
 
I wouldn't worry about it.
Just run all the taps for a while including hot.
At worst it sounds like bleach block and the dilution levels will be so low after flushing the system the risk to health will be miniscule.

Can I suggest you flush the loo next time after you have shut the water off and before you drain down.
 
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