Can't get shower pump to work without opening taps

26 Feb 2008
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United Kingdom
Hi just in the throws of fitting a bathroom.

I have a Salamander RHP75 supplying water to two bathrooms. Both hot and cold feeds from the CWT in the roof. Everything works fine from the taps but when I turn on the shower value, a cerramic cartridge manual one it does not have enough flow to do anything other than drip. This does not then trigger the pump so i have to open a bathroom tap to start the pump. Turn tap off and everything is fine.

Any suggestions on how to increase the flow? The mixer is meant to be a low pressure one. The distance between the shower head and outlet of tank must the only 30cm. The pump is on the floor under the bath. All pipework is 22mm except the last 2m to the mixer as this is in the roof and chased into the wall. Can't lift the CWT as its already as high as it will go.

Would changing this to 22mm work?
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you have the pump under the bath. pipework back up to the loft then to the mixer. don't make any sense
why doesn't it go from pump straight to mixer instead of a lap round the loft.
Hi Seco Services

you have the pump under the bath. pipework back up to the loft then to the mixer. don't make any sense
why doesn't it go from pump straight to mixer instead of a lap round the loft.

The 15mm shower tails and cutoff valves were already in the roof and in the wall as i ripped out the existing shower force pumped shower.

Would it make a difference if i was to reroute under the floor and up to the mixer in 22mm? I'm putting in a wetroom concealed tray but i can always go under it. I thought the flow rate would be dependant on the difference between the HWT and the shower head despite the distance. I guess i need more pressure to push through the cartridge so the flow activates the pump.
i always try to keep pipework low if poss rather than going up then down.
the rhp pumps need about 2ft or more from the cws to showerhead. or they go to a negative head situation like yours and reduce the flow and won't start the pump.
as you say your showerhead may be 30cm from cws but your pipework in loft is less than that.
have you any isolation valves in pipework ?
or you could try removing the non return valves in shower mixer, as they can restrict flow as can certain isolation valves
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I do have two isolation valves 15mm in the roof. Perhaps I will try removing these. It must be on the limit as on the odd occasion it does start.

Currently I have no Salamander S Flange fitted Would the lack of a flange and thus air bubbles make the pump switch less sensitive?

Fitting one is my next project do you recommend Salamander S Flange or something different? At the mo I only have a single hole at the top of the cylinder with a single pipe teeing off up for the vent pipe and down for the pump feed.

yes salamander flanges are ok better than taking feed from the hot supply.
as for your isolation valves a lot do restrict the flow.
i always fit full bore lever valves to showers. that could be your problem as you say your on the limit.
remove one and check if it's full bore or restricted to about 10mm
Thanks seco services

The 15mm iso valves are definitately restrict ones. I'll get out the ladder and remove them tonight.

With changing the outlet on the cylinder is it just a matter of unscrewing the old one (looks like a 22mm compression fitting on the top presumably with a male screw into the cylinder) and swapping it over.


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