Shower & pump problems All aspects of plumbing questions and answers, help, tips and information

[anty-a]

Somebody please help! We've recently fitted a new bathroom and have installed a Salamander RSP50 pump (in the airing cupboard) connected to a Grohe Grohtherm 3000 Bar mixer shower with a movario 5 shower head onto our gravity fed water system.

When we turn on the mixer the water trickles out and on many occasions the pump will not kick in (sometimes it will after a few seconds) However, if we take the shower head off and lower it - it then kicks in.

Once working and the showerhead is replaced in the holder, the shower is fine for a short while but then pressure slowly reduces and on some occasions the pump totally stops. Its really frustrating as we were all excited in finally having the bathroom finished! Any help anyone can give would be gratefully received.

[chris_on_tour2002]

the problem is that the pump is not activated until it senses a drop in pressure, ie it senses that the water is flowing.

in other words the water must flow under its own impetus FIRST, before the pump will work. the water has to push the pump in order for the pump to push the water. it sounds like you don't have the pressure, or 'head' in the first instance. as its gravity fed, in order to activate the pump the water must flow sufficiently for the pump to register it. by adding the pump you have created extra resistance for the water to initially flow, so if you had low pressure to start with it will be worse now. i deduce this because you say that the pump kicks in if you lower the shower head. by doing so you gain more 'head' thereby giving the water the force it needs to trigger the pump. if that's the case then really the only answer is to continue to lower the head of the shower to get it started.

having said all that i find it strange that once the pump has started up that the pressure gradually reduces. this suggests that there is a problem with the pump. might be worth reverting back to the supplier or even direct to the manufacturer, it may be an issue that they are already aware of.

another possible cause is with the non-return valves in the shower unit itself. i have encountered a similar problem before. the NRVs were for a high pressure system, but as the shower was pumped it neededthe system pressure to be strong enough to push open the NRVs to make the water flow in order to activate the pump.... if that makes any sense. i wonder if perhaps they are high pressure valves and they are gradually closing during operation, stemming the flow - though with a 3000 bar pump that shouldn't be an issue!!!!!!!! ;)

the valves are easy to change though it will mean contacting the manufacturer. i did, crosswater was the brand. they posted me two low pressure NRVs, talked me through how to change them which i did and it was simple and straightforward. and it cured the problem.

only other suggestion is that the pump is sucking the water from the tanks quicker than it can be replenished. are they of sufficient volume to satisfy the requirement for the flow rate of the pump? you might want to check that the pump has been installed correctly and that it has its own independent feeds from both hot and cold tanks.

[anty-a]

Thanks for the reply mate - this makes a lot of sense. I've contacted the pump supplier and am awaiting their response. Im thinking the NRV theory also sounds possible - so I'll also contact Grohe and see what they say about them supplying low pressure ones

[speedygonzarlis]

sounds to me like you have negative head, as you lower the shower head you are then getting positive pressure ie the pump kicks in.
if that is the case you need the salamander rsp100 negative head pump,
did you fit an ******* flange into your cylinder, its a must with a high power pump otherwise it can suck in air and get an air lock in the pump!

[anty-a]

more info - and after a bit more investigation last night...

Removing the shower head and turning pump off I have about 2 ltrs per minute - when I hold the shower pipe up to roughly where it would be when the head is in position its mor like 1 ltr per minute.

When running the shower with the pump - the pressure slackens off after about 1 minute. - the pump then starts making a different noise (less constant sound and noisier). If I then turn the mixer off and then on again it returns to a good flow (for another minute!)

I have a 50 gallon cold water tank. This is not being drained dry by the shower

The connectors on the inlet and outlets of the pump are 15mm

The feeds from the cold and hot tanks are dedicated feeds. The cold water tank has 22mm coming out of the tank which changes to 15mm just before it comes down into the airing cupboard. All the pipework to the pump and from the pump to the bathroom was done by a plumber when we recently had a new central heating system installed. I did the plumbing from the bathroom floor up to the shower.

The pipe from the hot water tank comes out from the side (******* flange?)

Does this change anything?!

[speedygonzarlis]

sorry i got it wrong its an esp 100 pump and your cylinder must have an S flange installed otherwise it just pulls air in, have you checked to see if you have negative head? if the pump is getting noisier and flow stopping this defo sounds like air getting in! S flange will cure it!!

[anty-a]

Thanks I've had another listen and I'm thinking your diagnosis might be the correct Speedy!

It does sound like air may be getting in to the hot water side of the pump (when the pressure drops and the noise starts) The plumber put in the outlet from the new hot water tank to the pump. It comes out of the side of the tank - presumably using an e s s e x flange - so I guess your saying if I change this for the salamander s flange that goes in the top. What would happen to the current outlet? Can this be capped off somehow?

I've had a response from Salamander....

"The pump itself requires a natural flow (without the power onto the pump) of 1 litre in 30 seconds or under on the hot, cold and mixed settings to operate.

From the sounds of the issue that you have this is down to borderline negative head.

The best option would be to fit either RCM3's to the pump that you have which is a negative head conversion kit or exchange the pump and upgrade the pipework to an ESP50CPV."


I've ordered the RCM3s which I think will help the negative head issue and saves me buying another pump!

[jonnygas]

anyone know about RCM3s in relation to salamander shower pumps. negative head conversion kits?
cheers