Mains contaminated water supply

[rov1100]

If the bathroom toilet and kitchen sink and on the ground floor, both run off the cold water mains supply, can the drinking water or washing machine fill be contaminated from flushing the toilet? If so what would prevent this?

[Old_Geezer]

I believe it illegal to allow water to flow back into the mains supply. No expert but the pressure of the mains wuld probably mean you were forcing it back, so it doesn't happen.

Anyway, the water flows into a cistern before passing on to the toilet so how could it possibly flow back through that lot ?

[Buenchico]

Only the cistern for the WC is fed from mains supply. That's completely separate from the toilet bowl itself, so no contamination can occur.

Further, the flow of water is in one direction only. The pipe leading into the WC cistern is akin to a hose pipe being used to pour water into a bucket. It wouldn't matter how filthy the bucket was, it couldn't contaminate the water in the hosepipe (or in anything else fed by the same water supply).

Chris

[boxtops]

No, the flushed water from the toilet should go straight into the downpipe, into the drains and ultimately to the main sewer - it shouldn't be going anywhere near your fresh water intake.

[rov1100]

I believe there is a law that states you must have a non return valve on your water supply but where it is placed and why I haven't the foggiest. I believe its to stop back siphonage of contaminated water.

[AlBags]

Covered by Byelaw.
For instance .. Storage tank fly screen and covers are byelaw 30.

[tezestwing]

If the over flow is at the same level as the ball valve, then contamination can certainly occur if the ball valve becomes submerged,so not complying with bylaw 30.
Best to ajust the valve float arm,to prevent this unhealthy situation.
HTH Tez

[rov1100]

From what I have understood about bylaw 30 it concerns stagnant water in the loft space. My problem though is that the downstairs loo, bath and kitchen cold water tap all operate directly from the mains. Sometimes the shut off valve in the loo fails to operate (I'm not sure why) and clothes in the washing machine have a brown mark over them and the tap water is cloudy and tastes funny. Seems like I need to call in a decent plumber.

[Old_Geezer]

I'd have thought it strange for even back contamination to cause that. Not that I can claim expertise.

Perhaps run the tap and see if it clears? It's not unknown for the supply company to not get their chemicals exactly right. And check for washing machine problems causing the dirty marks?