Shower Pump Problem

[RSF]

We have just had a new loft mounted shower pump to feed our 2 Mira Showers. All is well they work fine.
What we have found however is that when we use then turn off some of the hot water taps in the house quickly, the pump starts to pulse. We have to then run the shower for a couple of seconds to stop this. If we turn of the taps slowly it doesn't happen. Any ideas?

 

[giblets]

Is the pump suitable for mounting above the hot water cylinder? Normally booster pumps must be fitted at floor level adjacent to the cylinder. Check in the installation instructions. Also, did the installer run a seperate hot water supply from the cylinder to the pump?

 

[Balenza]

We have just had a new loft mounted shower pump to feed our 2 Mira Showers. All is well they work fine.
What we have found however is that when we use then turn off some of the hot water taps in the house quickly, the pump starts to pulse. We have to then run the shower for a couple of seconds to stop this. If we turn of the taps slowly it doesn't happen. Any ideas?

Im not sure of the design of your particular shower valve but some shower valves have a single output volume control and the water is pre-mixed in a chamber in front of this valve.
In these types of showers, there should be NRVs in the feeds (sometimes built into the valve. These may be missing or defective.
Alternatively, your hot feed from the HWT is shared and not a dedicated one (Surrey or essex flange).
So when someone opens the hot water tap downstairs, there is a sudden drop in the pressure on the hot side. The cold water momentarily flows to make up this drop. As a result the flow switch turns on the pump.

 

[RSF]

Hi, thanks for your comments.

The pump does have a loft mounted option, (Salamander) and I have consulted them over the correct installation several times. The pump has a dedicated Essex flange feed from the HWC.

Just to clarify, the showers and the pump work fine, only when a domestic hot water tap is turned off quickly does the pump pulse. No water escapes the mixers at all when this happens. The pulsing is stopped by running the shower for a couple of seconds and then turning it off.

As said before, closing off the taps slowly avoids the problem, but if you don't get it quite right it sets the pump off in the way described.

Regards

Russ

 

[giblets]

I suppose there is the possibility of an air pocket trapped somewhere in the pipework and acting like a shock absorber which, in turn, is causing the pump flow switch to operate intermittantly.

Out of interest, are your taps the 1/4 turn type or the traditional "turn the knob" type?

Regarding the shower pump, does it have a pressure vessel or flow switches?

 

[RSF]

Hi the kitchen sink tap is a modern type lever hot/cold mixer, so it's far easier to shut off too quickly than a traditional type tap. I notice that this problem happens as a result of using this tap far more readily. The other taps in the house are 'turn the knob'.

I think the pump has flow switches.

I have consulted Salamander this morning and it seems they have heard of this before and describe it as 'water bounce'. They are sending out a non return valve and a diagram as to where it should be placed. I can only imagine it will go on the DHWC pipe out of the top of the HWC.

I'll let you know anyway, thanks for the input so far.

Russ

 

[RSF]

I was wrong. They sent me a neat little non-return valve that fitted onto the thread of the pump hot outlet. Not a big job as the connectors have isolators. Problem solved.