Showermate 1.4 Twin - hot water problem - advice needed

[JCB2007]

I have recently replaced a Monsoon 25T pump for a second hand ShowerMate 1.4 Twin.

I was expecting it to be a quick like for like replacement, but it appears the hot water is being overridden by the cold. I primed the pump by running the shower with no power to the pump for a period of time.

The pump runs when I turn on the shower with the thermostat on cold , but as soon as I turn the thermostat to introduce hot (a quarter turn), the pump cuts out. It pulses for a bit first then stops. On the old pump, a half turn was sufficient for a warm shower.

The shower will run without hot and the temperature is just about bearable,some hot must be getting through as it is not completely cold.

The forums suggest an air block. I ran the shower with the pump off, to see if that clears the blockage. I have cleaned the in line Y filter on the hot side.

I can feel the hot side copper pipes feeding the pump on the incoming and out going feeds are hot.

I also tried setting the incoming hot water to 65 degrees, that made no difference. Then I read it might be too hot , so I tested on 50 degrees. It made no difference.

All isolating valves are open.

I'm out of ideas or things to try.

Could it be an air blockage in the pipework/pump, as I have no primed the pump correctly or for long enough to flush out air bubbles ?
Faulty thermostat ?
Dodgy flow switch on the hot side ?
Do I have the wrong pump ( my water tank is in the loft, the hot is T-eed off the hot water cylinder, the pump is next to the tank on the floor)

Any advice you can give would be appreciated.

 

[kbdiy]

Assuming you haven't made any pipework changes then I would think it could be an airlock. Priming the pump is usually achieved by removing each of the pump connectors and slowly allowing water to backfill through the pump until it flows out of the connector. Needs to be done separately for hot and cold. Reconnect and run hot and cold with the pump switched off should confirm it is properly primed, then switch on and away you go.

Of course, as this is a secondhand pump then who knows if it was any good to begin with?

 

[JCB2007]

I made a minor alteration on the incoming hot and cold feeds, as the tails were too short to reach the new pump location. I extend the tails by 3 inches.

I'll prime the pump properly as you have suggested. Thanks.

 

[JCB2007]

So I have now primed the pump and still no hot shower. But I noticed the flow on the hot side was very poor.

I checked the incoming hot and the pressure is fine. So something must be blocking the pump.

I took the pump out and decided to blow into the tubes. On the cold side the air passed through, an audible click was heard which I presume is the flow switch.

I tried the same on the hot side and it was virtually impossible to get air to go through. Also I could not hear the flow switch.

On the out going supplies I could see a small rubber grommets, which when I blew on the cold side flipped up , so I checked it was moving freely on the hot side, which it was.

I'd like to know if blowing through the tubes is a good test,as the symptoms I am experiencing is that hot is not flowing.

I have put the old pump back in (which requires a kick to get it to start, hence the need for a replacement) and I have a hot shower again.

Any ideas people ?

 

[StuartTurnerLtd1]

Hi, second hand pumps are a complete waste of time in my opinion as they have been taken out for a reason normally unknown to buyer. If shower works fine on old pump (25T) but need to kick it to get it going it tells me your 1.4 is duff. For the price on internet I would replace with newer version 46407 1.8 showermate. Same performance as the 1.4 just measured differently.

Plastic ended pumps are not a viable option for repair due to cost of parts, risk, time and effort V's cost of internet sales.

Hope this helps.

 

[jeff the gasman]

Has a gate valve failed or some other restriction?
Does the shower get hot water without pump switched on?
If it does the pump is fooked.
Jeff