Pulsating Shower Pump

[didydave]

I have just replaced a shower in a clients house. The shower i took out was a simple leaver shower with hot and cold water coming in at the sides and mixed water coming out of the the third pipe. the one i have put back in is exactly the same stype and infact i used a lot of the original fittings to make the connections. All the fittings are consealed behind the tiles with a chrome leaver tap and the hose only showing. The pipe work behind the tiles were not changed and neither was the elctric pump.
The problem i the client is now having is that when the shower head is over a certain height the pump pulsates. Is this a faulty shower pump or something that i have done? the only that was fitted that was not according to instrcutions was that the shower mixer was fitted upside down, as was the original one, so that the hot feed was on the right not the left.
If you have any ideas please let me know.
David

 

[NickH]

Pulsates how ? does it switch on and off or surges ?

 

[didydave]

it switches itself on an off very quickly, pulsing

 

[sagsy]

is the pump a salamander pump if if it you will need to contactact salamander and get them to send yiu a backflow valve that is fitted on hot water outlet on pump.

 

[didydave]

No It's not a salamanader pump in fact i have no idea who the pump is made by. does it matter if it's salamander or not? I will check with my local suppliers to see if i can get a backflow valve for it.
Thanks
Didydave

 

[sagsy]

The reason I said this was I had the same problem when I fiited the salamander pump. I contacted them and they told me to fit the backflow valve on the hot outlet, they even supplied the valve FOC. you could also just fit a double check valve on the hot outlet pipe going from pump to shower.

 

[didydave]

I have contacted Salamandar, thru their website and await a conversation however if a double check valve solved your problem sagsy then it's worth a try. certainly better than ripping out the new shower and old pump.
cheers.

 

[ajs heating]

sounds like the pump is on the border line of a positive/negative situation.
if your not getting the correct flow per min gravity it will pulse or not start at all.

i would of fitted the mixer the right way round and changed the hot/cold on the outlets from the pump.

 

[Chris R]

Re contacting Salamander - I have tried a few times to contact them via the website and they never reply - it is best to give them a ring. I have the smae problem - Salamander called it 'ram-rodding' and have sent my customer a free valve to sort it

 

[didydave]

I wish i had turned the shower round now but sadly that is no longer an option as the whole thing is now tiled however if this is rma rodding with a check valve stop or make the problem worse? Oh and the old shower was fitted upside down with out any problems so why would the new one, which is exactly the same design, have this problem?
Thanks to all who have replied to my plee's

 

[Alanka]

I do not believe the orientation of the mixer unit has anything to do with the pulsation problem.

The pump motor is activated by flow of water in the correct direction through a flow switch in the pump -- usually a pair of switches, one in the hot and one in the cold pipe, either of which turns on the pump.

Turning on the shower outlet valve usually allows sufficient flow to do this. If the flow falls below a certain rate the flow switch cuts out the motor. Raising the shower rose reduces the natural flow (due to reduced head of water). If your pressure is borderline anyway (cold water cistern only a bit higher than the shower rose) the flow can be so low when you turn on that the flow switch only just operates and starts the motor. But as soon as the pump starts to suck water via the pipework a slight partial vacuum occurs upstream of the pump. This causes a brief backflow of water in the wrong direction, which instantly deactivates the flow switch(es) and shuts off the pump.

The natural flow then restarts the pump which triggers the on/off cycle again, leading to pulsations.

Putting a non-return valve (single checkvalve) on the hot water outlet of the pump prevents these brief backflows, and so stops the pulsations. I'm not sure why you use the hot water outlet rather than the cold, but it may be because the hot supply usually has a lower flow/pressure due to longer pipework from cold water cistern to the pump.

 

[ajs heating]

I do not believe the orientation of the mixer unit has anything to do with the pulsation problem.

The pump motor is activated by flow of water in the correct direction through a flow switch in the pump -- usually a pair of switches, one in the hot and one in the cold pipe, either of which turns on the pump.

Turning on the shower outlet valve usually allows sufficient flow to do this. If the flow falls below a certain rate the flow switch cuts out the motor. Raising the shower rose reduces the natural flow (due to reduced head of water). If your pressure is borderline anyway (cold water cistern only a bit higher than the shower rose) the flow can be so low when you turn on that the flow switch only just operates and starts the motor. But as soon as the pump starts to suck water via the pipework a slight partial vacuum occurs upstream of the pump. This causes a brief backflow of water in the wrong direction, which instantly deactivates the flow switch(es) and shuts off the pump.

The natural flow then restarts the pump which triggers the on/off cycle again, leading to pulsations.

Putting a non-return valve (single checkvalve) on the hot water outlet of the pump prevents these brief backflows, and so stops the pulsations. I'm not sure why you use the hot water outlet rather than the cold, but it may be because the hot supply usually has a lower flow/pressure due to longer pipework from cold water cistern to the pump.

we have already been down that path and was chosen to be ignored.

 

[didydave]

Hi AJS and Alanka I have now had a reply from Salamandar pumps who say the following.

" Thank you for your e mail for what u are experiencing the non salamander pump is not producing enough pressure to shower head after a certain height which in plumbing terms is a negative head.

A non return valve would only make the matter worse and restrict the flow even more. You possibly may need a momentary pull cord switch to enable the pump to keep running when the shower head goes over a certain height.

Please call the following number for further assistance 0845 129 5010"

What pray is a momentary pull cord? I ask.
Never mind, the client has now told me that the problem appears to have solved it's self and the shower is now not pulsating so i think that it may have been a small air block in the rather complicated pipe work under the floor.
Again thanks for all the advice. What a great way to get help.

 

[Alanka]

Ha-ha! Who needs plumbers? The problems solve themselves if left alone!

Seriously, though, I would guess that a 'momentary pull cord switch' is a switch that you can operate safely from the shower, that bypasses the flow switch(es) and so starts the pump even when there's insufficient flow.

When you let the cord go the switch reopens, but the flow switch(es) stay closed due to the pumped water now flowing through them.

(Or maybe the switch reopens itself after a very short time period even if you haven't let go?)

Cunning, eh?