Shower Pump failing?

[leighivansmith]

Hi all, new to the site but spent some time searching and could not find a report of this problem.

I have a gravity fed system located in the loft of my house. This system consists of a boiler, hot water tank and a raised cold water storage tank (for hot water only) in the loft. I have mains cold water to all cold water taps.

I have a shower in the en-suite that is connected to an old twin impellor pump located in the loft. The hot water feed is taken from a T connection after the hot water tank and the cold water is taken via a dedicated feed from the hot water raised storage tank (not mains).

The problem we are having is intermittent pressure issues (medium dropping to low pressure) usually resulting in low temp as well. To clear this fault, I take the shower head off and run the shower with the pipe in the shower tray. I run the shower on full hot / full cold for a shot period (30 seconds or so) and the pressure increases. I reconnect the head and then we get normal (medium) pressure from the shower.

The other problem is that when we finish using the shower, we turn the shower off but the pump continues to run (sometimes for several minutes). To clear this I have to do the same as above but the pump will continue to run for about 15 – 30 seconds after.

A final item, we have noticed that if you turn a hot tap on in the bathroom or kitchen, you hear a short burst from the pump in the loft (2-5 seconds). Not sure if this is normal or not – it has always done it.

The pump is quite old and I can find no markings for make / model. It only supplies this single shower. I have cleared all filters (there is one on the hot and cold pipe), ensured that flow sensors are securely fixed to the pipe and I have replaced the gate valve on the hot water supply (it was faulty and would not fully open). None of the above has improved the issues and they are happening more regularly. It used to be once a week now it is every day and even every shower.

My questions to the folks on the Forum:
1, I think the shower pump is failing but I can find no description of intermittent problems – they sound like they either work or they don’t so I wanted to check with folks on the forum if the problems described above really justify the need to replace the pump.
2, My wife and I really like a high pressure shower – our last house had mains pressure hot water so we always had high pressure showers. What pressure pump would you suggest to achieve a high pressure shower?

I know my descriptions of low, medium and high are relative to me but I hope it gives the impression of the problem we experience. Even with the pump performing at its full pressure, it feels quite weak…

Thanks in advance for your help.

 

[busterwebb]

I'm not an expert, but these are things that have bitten me in the past with similar faults to the ones you describe:
1. In one installation I had a twin impeller pump driving a thermostatic mixer shower. Flow used to diminish to nothing during a shower corrected by running cold water through the shower. Problem turned out to be hot temp to the mixer input was exceeding its temperature spec. I spent ages thinking it was the pump.
2. One of the flow sensors on a negative head twin impeller pump failed and this gave odd results including random turn on/off. In the end I bit the bullet, bought another pump and it worked fine.
3. Is there any chance the pump is sucking in air through a leak, or through problems with the cold or hot water tank flanges?
Just some stuff to try.

 

[leighivansmith]

Thanks for the ideas.
I was also thinking the mixer could be the cause of the fault. This shower is fitted into the wall so I have no way to remove / inspect it that I know of - any ideas?

I know that when the shower is working - the hot temp gets much hotter than what we have it at usually so it implies that the shower is working correctly...

I have checked and the flow sensors are connected. I am struggling to find replacement sensors to test if it is a sensor fault. Most modern pumps seem to have them built in where this one they are external and attached inline to the pipes.

When I replaced the gate valve, there was a minor leak at the join that I have since corrected. I did have to drain the entire hot water tank to replace the valve but I am sure there are no airlocks. I ran water through all hot water taps including the shower (pump off) for several minutes to ensure free flow of water...

 

[busterwebb]

I measured the hot water temperature, which at 80 degrees was above the specification of the triton LP mixer. At this temperature the mixer just shuts down until it cools. Cure was to fit a thermostatic mixer valve which clamped the water feed to 65C.
On a different fault, the sensors on the Salamander pump were pressure transducers inside the sealed central electronic control box. Almost impossible to test, i'm afraid. Older pumps use magnetic flow sensors with either reed relays or Hall effect sensors, which are easier to test.
It's not just airlocks which screw up pumps, but also sucking water through a cold water flange too near the tank surface (you can usually see the vortex forming) or from the hot water tank if you don't use an essex flange.