Choice of pipe for hot water secondary/recirculating system

[Failte]

What plastic based / barrier pipe can you use in a hot water secondary/recirculating system. I note Hep20 and Polypipe make it clear in their specs it must not be used. Other than copper what do you use.

 

[ShaunCorbs]

Mlcp

 

[Failte]

thanks very much

 

[windyboy]

Also can't use JG Speedfit.:

1

What can happen if you do use (some type of) plastic pipe on a recirculating system:

 

[RBG]

Is that due to the constant high temp?

 

[Failte]

I have spoken to the manufacturers polypipe etc and it is because of the higher content of oxygen in the water, it wears the joint connections away and it can short time or a longtime so they say. I wondered if it is like cavitation your get with ship propellors?

 

[windyboy]

My understanding is that it's the combination of of high temp plus regular replenishment of water (when hot water is drawn from the system). That means that the circulating water is well oxygenated, which can cause degradation of the plastic. So JG Speedfit (for example) is ok on closed central heating circuits but not recirculating HW.

 

[windyboy]

Sorry to repeat. Was typing when Failte posted.

 

[poorman]

How easy is it to retrofit a hot water circulation pipe on an unvented ASHP, would it need a pump, the tank is upstairs

 

[ShaunCorbs]

How easy is it to retrofit a hot water circulation pipe on an unvented ASHP, would it need a pump, the tank is upstairs

Not easy what’s the issue ?

 

[poorman]

W

Not easy what’s the issue ?

We have to run nearly 5 litres of cold water in the bathroom wash hand basin before we get any hot water, that's 5 litres of cold water dumped into the hot water tank which isn't very economical.