Increasing cold pressure to a shower mixer

[u38cg]

Hi folks,

I have a shower mixer fed off a combi and a cold tank. Hot pressure and flow is excellent; cold is more problematic.

At tap height, flow and pressure are fine, and they mix no problem. However, the tank is only about 2.2m (roughly) above tap height and doesn't provide enough pressure to provide an adequate flow to the shower head. In fact, the hot water actually starts pushing its way back up the cold feed.

What are my options here? I have insane mains water pressure (ground floor of a four floor tenement), and it looks like it would be simple enough to reroute the bathroom cold supply onto the mains through a pressure reduction valve. This would also presumably be cheapest, and easiest for a fool like me to not screw up.

Would a low pressure mixer work here with mis-balanced pressures ?

The other option seems to be a shower mixer pump, but (a) limited space, and (b) expensive.

As usual, all thoughts welcome!

 

[stem]

If you have a combi, it's normal to use the cold main supply to give a balanced feed for a shower. (The hot supply will have slightly less pressure due to the pressure drop across the boilers heat exchanger)

My guess is your shower was originally fed from a hot water cylinder, which also was supplied from said storage tank, and when the combi was installed, the cold water feed to the shower was left as it was.

I believe water utility companies have to supply water within certain pressure limits, so I can't imagine why you would need a pressure reducer. It's the same main that feeds your combi. Is that reduced?

 

[u38cg]

I am not sure exactly what is being fed into the combi, but certainly whatever is coming out is at nothing like the actual mains pressure - my kitchen cold is on the mains and if I turn it on full I can soak the entire kitchen in a matter of seconds. I can't see a reducer anywhere, but quite a lot of piping in this place is well hidden!

We have an electric shower fed off the tank, which is why the bathroom cold isn't mains fed - the flow is however miserable, and the combi is decent, so putting a mixer in seemed the sensible move.