i need help identifying a pipe!

ive got a tank in the loft which has 2 outlets at the bottom. One is a copper pipe which fills the hot water cylinder, and the other is a grey flexibible pipe with a red stopcock on. Inlet and overflow are obviously at the top of the tank.

My cold water is all mains fed, as if i turn off the main cold stopcock in the kitchen none of the cold taps work.

i cant work out exactly where this grey plastic pipe goes as it vanishes down into the walls.

If i turn the stopcock off on this grey pipe (its normally open) it doesnt seem to affect anything, all the cold taps still work and hot water tank still fills up.

Theres a seperate expansion tank for the heating system which has a mains water fill via a ballcock and this all works fine regardless of whether the grey pipe is on or off.

any ideas? It could be to drain the tank, but i cant work out where it would drain to (and the stopcock on this pipe is normally open).

reason for asking is the house is empty and i had a some frozen pipes last weekend when i was over. Mains water was off, and doesnt appear to be any leaks, but to be extra safe i decided to turn this tank stopcock off in case the grey pipe had also frozen and developed leak which would potentially drain the tank while i was away from the house for the week.

Shower feed?

hmmm could be. i know the shower has its own hot feed from the hot water tank so it may have a separate cold one from the cold tank rather than a mains water feed. I guess this could be so its less likely to suffer temp fluctuations depending on demand from other taps?

I'm back there tomorrow so i'll check it then.

It could well be a cold shower feed, they're commonly fed from the header tank to equalise the pressure between hot and cold.

go with a shower supply to ensure balanced pressure at the shower outlets, turn it off and check if you have cold to the shower?

could be to a pump also, if you have one as it is illegal to connect the water main to a pump.

It's not 'illegal', it is 'against the regulations'. Don't worry the police won't turn up and arrest you!

C

they should though

it is illegal. that is the main change from the alteration from water by laws to regulations which happened about 10 years ago. It is now a criminal offence, similar to breaking the gas safety installation and use regulations, granted you may not be arrested but the potential fines are quite large.