Hello plumbing experts

[pontiff]

Hi there,

My plumbing skills are pretty basic so apologies for all the future daft questions.

I'm researching into replacing water supply to downstairs toilet with a rainwater feed from an outside tank.

I was wondering if I can simply cap off the cold mains supply as it comes out of the wall or do I need to cut into the walls to find where it tees off.

I think it might be treferred to as a dead leg? Is there a minimum safe length or is it simply a no no?

Thanks in advance,
Phil

 

[Dan]

Welcome to Plumbing Forum | Plumbing Advice | Plumbers Forums | A forum for plumbers advice in the UK!

Hi pontiff and welcome to UKPlumbersForums.co.uk!

 

[JPlumbUK]

Cap it off, will be fine.

 

[john.bell55]

Before doing so refer to the Water Regs. Rainwater is not water supplied by The Water Undertaker so suitable back flow prevention would have to be installed as the tank is topped up from the mains.

Considerations for fitting a rainwater collection system to an existing property.

• The external drainage from the roof needs to be modified to bring the water to a central point.
• Access for the tank and excavation is required.
• Internal plumbing is usually required to be seperate out the drinking (incl. bathing) water from the non-drinking water (WC, washing machine & outside tap.

Depending on how the water is to be used it may be required to be upgraded to fully drinkable standard (potable), by using non-chemical ultra-violet sterilisation.

 

[pontiff]

Thanks for the replies, I'm only doing it for the toilets so as not to make it too complicated.
The mains backup is an issue I've been considering. Rather than installing a header tank in the attic with a mains backup, I was thinking of a pumped direct rainwater feed to the toilet cistern through one inlet valve, a mains feed backup ( with shut off valve) through a second inlet valve ( where the old cistern overflow pipe was- now using a syphon with an internal overflow). This would give about a 15cm air gap and the only way contamination could take place is if the valve and the overflow both failed. Even then it would have to get through a closed valve and a double check valve.

Just thinking out loud really, the most likely approach will be to cap it off and reconnect if the rainwater fails.