Expansion for Undersink Heater

bette

Morning peeps

I'm looking to install an undersink water heater. They specify that the feed pipe can be used to accommodate expansion: To achieve this the pipe work between the nearest cold water draw off and the water heater must be of sufficient volume to accommodate the expansion.

So for a 10 litre heater they recommend approx. 3 metres of ½" pipe. Now my question is; can I double up the pipe with a "U" bend due to lack of space?

Thanks in advance

Buford T Justice

What sort of a water heater is that? Not heard of having to run 3m of pipe before

Pete67

As long as there is 3m of half inch pipe or equivalent volume between the water heater and the closest isolating valve upstream then you will be fine. If the only isolating valve is the mains stopcock coming into the house then you will be fine too as the rising main will also be available to accomodate expansion.

bette

Pete67 wrote: »

As long as there is 3m of half inch pipe or equivalent volume between the water heater and the closest isolating valve upstream then you will be fine. If the only isolating valve is the mains stopcock coming into the house then you will be fine too as the rising main will also be available to accomodate expansion.

Just looking at the manual. It says that there should be approx 3 meters between the nearest cold water draw off (the cold tap?).

Billy Bunting

I've fitted quite a few of these electric hot water storage units some just feet from the tap, i have always relied on the pipe from my tee on the supply back to the stopcock for expansion, never had a problem.
Be sure to fit the PRV that comes with the heater though.

bette

Billy Bunting wrote: »

I've fitted quite a few of these electric hot water storage units some just feet from the tap, i have always relied on the pipe from my tee on the supply back to the stopcock for expansion, never had a problem.
Be sure to fit the PRV that comes with the heater though.

Thanks guys. I think the expansion recommendation must apply to the UK, maybe they have a stronger mains pressure.

I'll go with that then!

bette

bette wrote: »

Thanks guys. I think the expansion recommendation must apply to the UK, maybe they have a stronger mains pressure.

No, the physics are the same but in Ireland there is no regs for fitting them. If it were my house i would fit it to UK regs/standard, this will deal with expansion and there is a 6 bar pressure relief valve with a 1/2" connection so the pipework can terminate to a safe place.

You can get a small expansion vessel, some manufactures supply them when you can't get the length on the cold side.

Sparkpea

sounds like the redring manual but to answer your question yes its ok to double the pipe back to get the correct length they specify. I try to use the ones with a expansion vessel now though.

A lot of the units i look at have the chrome discharge valve(8bar) fitted to the cold water inlet on the heater, because it's a checkvalve as well they stop any expansion and push out the front gasket causing wet mayhem.