Shower and combi advice

ants83 · 15 Sep 2017 at 15:00

Hi. Moved into a house with a digital mixer shower. This pumped water from a tank to the shower.
I have since upgraded and now have a combi.
The digital pump is still there but I'm presuming I don't need this as the shower will be mains fed?
Any ideas?

GeForce · 15 Sep 2017 at 15:02

Correct, you can't have a pumped shower with a combi boiler.

On some digital mixer showers you can swap the mixer unit for a non-pumped version, otherwise you'll have to change it.

ants83 · 15 Sep 2017 at 15:21

Thanks GeForce. Would I be best changing this asap as I am guessing the extra pressure is no good for the shower or pipes?

GeForce · 15 Sep 2017 at 15:28

I believe it is illegal to pump a mains circuit, so it should be removed ASAP. I'm surprised the boiler installer did not remove it and fit a normal mixer instead.

I'm not sure what the consequences of using it would be, probably depends on relative pressures. Certainly the pumped mixer won't be rated for mains pressure so it could leak or break in some other way. The pipes themselves should be fine (they'll be at mains pressure all the time now, pumped shower or not).

ants83 · 15 Sep 2017 at 15:30

They mentioned it but I was away when the boiler was installed and presumed they changed it. Looks like they didn't. Thanks for the information, will get this removed asap in this case.

NoNameNoNumber · 15 Sep 2017 at 20:08

You could end up siphoning next doors' bath water into your mains water supply... Straight into your cuppa

robj20 · 16 Sep 2017 at 07:08

GeForce said:
I believe it is illegal to pump a mains circuit, so it should be removed ASAP. I'm surprised the boiler installer did not remove it and fit a normal mixer instead.

I'm not sure what the consequences of using it would be, probably depends on relative pressures. Certainly the pumped mixer won't be rated for mains pressure so it could leak or break in some other way. The pipes themselves should be fine (they'll be at mains pressure all the time now, pumped shower or not).

You can pump mains water up to 12lpm.

ants83 · 16 Sep 2017 at 08:14

robj20 said:
You can pump mains water up to 12lpm.

The gravity pump I have pumps at 1bar so I've read. I'm guessing the mains is just above that 1bar.
The pump is not rated to use with combi or mains though so still needs switching

robj20 · 16 Sep 2017 at 10:00

ants83 said:
The gravity pump I have pumps at 1bar so I've read. I'm guessing the mains is just above that 1bar.
The pump is not rated to use with combi or mains though so still needs switching

Mains is usually a fair bit higher, ours is 4 bar.

ants83 · 16 Sep 2017 at 10:35

robj20 said:
Mains is usually a fair bit higher, ours is 4 bar.

I see. So I have a 1bar pump on a 4bar mains. Sounds like I'm getting a plumber in!

GeForce · 16 Sep 2017 at 17:49

robj20 said:
You can pump mains water up to 12lpm.

I did not know this, thanks