Upgrading pipe between stopcock and thermal store

[Winty]

I have had a Gledhill Torrent thermal store installed, providing hot and cold at mains pressure at all outlets. My incoming supply is a black alkathene pipe, installed in the 1960s when the house was built. From there, a 15mm pipe runs to the thermal store, with a branch to the kitchen cold tap. The pressure is quite high (over 3 bar).

I have two thermostatic mixer showers, to which I have fitted Mira Eco shower heads, which provides an excellent shower (flow rate of 7-8 litres per minute) when only one of the showers is used and no other water is being drawn off.

I have reduced the impact on flow to the shower of other draw offs by fitting flow regulators to the basin taps and toilet cisterns (all capped at 4 litres per minute).

I now wish to make further adjustments to enable two people to take showers at the same time without a significant drop in flow. I realise that the best solution would be to have a new water supply pipe installed from the meter to the stopcock, together with upgrading pipes internally, but the cost and disruption would be too great.

I am wondering whether there would be any benefit in replacing the 15mm pipe between the stopcock and the Gledhill Torrent with a 22mm pipe which would then branch into two 15mm pipes, for hot and cold supply, at the inlet to the Gledhill Torrent. Would this improve the flow rate, or would it have no effect at all?

 

[Agile]

Its normal to supply a store or U/V cylinder with 22 mm.

How much difference it will make will depend on where the greatest restriction is occuring.

But at least it will do no harm.

Tony

 

[MIGEM]

The hot and cold connections should be 22mm anyway.
A direct will give up to 15 litres a minute and an indirect will give up to 18 litres with 22mm. The standing water pressure should be set at 3.5bar on a prv, and best with a minimum dynamic pressure of 1.5bar.

 

[Winty]

Thanks for the advice.

Do I need to replace the 15mm mains stopcock with a 22mm one?

As the internal diameter of the alkathene supply pipe will be about the same as that of a 15mm copper pipe, I cannot see the point, but perhaps I have missed something.

 

[powell30]

As has been said.....your flow rate is defined by the smallest bore of your run.....i doubt you will see any significant impovement by upgrading the internal 15mm.

You ned a 25mm mdpe run then 22mm from stoptap

 

[Winty]

I realise that the 15mm diameter of the pipes is a limiting factor. However, I also understand that there is an issue of flow resistance in the pipes and particularly at bends. There are at least four 90 degree bends in the 15mm pipe going from the stopcock to the thermal store. I was hoping that the replacement of this pipe with a 22mm pipe with three 90 degree bends would reduce the flow resistance somewhat, and therefore improve the flow rate. I would appreciate comments.

I have had quotes for 25mm mains supply, but they are quite high, because of the distance involved. If necessary, I was thinking of installing a cold water accumulator instread, which would be a cheaper option. I would be grateful for any advice about this.

 

[Agile]

I realise that the 15mm diameter of the pipes is a limiting factor.

Its not a "limiting factor".

A narrow pipe causes a high flow resistance. That required a high pressure to overcone the loss.

The lower the total resistance the more flow for a fixed supply pressure.

Upgrading any part of the pipe will help but any length of 15 mm will have the most effect on slowing the flow rate.

Irs usually £500-£1500 to upgrade a supply pipe.

Tony

Tony