Bathroom Pump pressure issues

[CaptainJack88]

Hey All,

After a bit of advice with our bathroom. The plumbing has been done like below for certain reasons. I've tried to keep the diagram accurate, so where the pipes are going up and down, then it resembles the pipes going vertically to a similarish height to real life.

We initially had a shower pump, however the problem was that the Shower 2 never engaged, I'm assuming because of the multiple ups and downs, and too much negative pressure not triggering the pump. This also caused issues with the bath and sink, as the mains pressure simply overpowered the hot water, so the pump never triggered until only hot water was being called.

We thought that maybe a universal pump would fix the problem due to pressurising the system and using pressure switches, but quickly realised that these double twin impeller pumps run hot and cold at the same time. If the hot was called for the sink or the bath, then it'd burn out the motor because there was no water movement on the cold side. Salamander do have a pump with a crossover that would help this situation, but after calling them, their pumps are not designed for this and warranty will be voided.

Our final attempt has been to use Shower Power Boosters. We have one on the hot and one on the cold. No issues starting the pumps now, but the pressure or flow is absolutely appalling. It takes a few seconds for the pumps to kick in, and when they do, you can see they barely make any difference. We actually get more pressure downstairs from just gravity


Has anyone got any other suggestions? We're at a bit of a loss what to do. It's been suggested to stick 2 power boosters in series, but i'm not really convinced this is going to solve anything.

Would 2 single Universal Shower Pumps works, one for hot, one for cold? I dont want these to cause issues with working against each other and causing some sort of back flow or similar.

 

[Johntheo5]

You won't burn out the motor if you dead head either the hot or cold end of a universal, however as the pump energy will heat the trapped water and will probably, depending on the dead heading time, cause seal failure due to to temperature rise, far more likely IMO, if the hot end is dead heading, I would have a word with Stuart Turner or Grundfoss as I think ST at least allow some (short time?) dead heading. If the cold end is the only end to be dead heading then you could consider installing a adjustable pressure relief valve or a suitable ABV (automatic by pass) that will give a very small flow of water which can be recycled back to the CWST until a demand for cold water, any centrifugal pump head will start falling with increasing flow rate. If you choose a 3.0 bar SS Twin then a 2.5bar PRV, if recycling back to the CWST will only pass probably 2 to 3LPM and will close once the demand is > this. I know of someone who did this many years ago but can't remember the exact pump head and PRV.


The two pump (singles) approach should certainly work but will need installing non return valves on any mixers.

 

[CaptainJack88]

You won't burn out the motor if you dead head either the hot or cold end of a universal, however as the pump energy will heat the trapped water and will probably, depending on the dead heading time, cause seal failure due to to temperature rise, far more likely IMO, if the hot end is dead heading, I would have a word with Stuart Turner or Grundfoss as I think ST at least allow some (short time?) dead heading. If the cold end is the only end to be dead heading then you could consider installing a adjustable pressure relief valve or a suitable ABV (automatic by pass) that will give a very small flow of water which can be recycled back to the CWST until a demand for cold water, any centrifugal pump head will start falling with increasing flow rate. If you choose a 3.0 bar SS Twin then a 2.5bar PRV, if recycling back to the CWST will only pass probably 2 to 3LPM and will close once the demand is > this. I know of someone who did this many years ago but can't remember the exact pump head and PRV.


The two pump (singles) approach should certainly work but will need installing non return valves on any mixers.

Thanks. Stuart Turner was impossible to actually get hold of to discuss, so all came from Salamander.
Regarding the 2 single pumps, this might be the easiest way to resolve, as bathroom is fully tiled, so the only accessible pipework are the feeds in the loft and airing cupboard.

Regarding the non return valves, is that a requirement? When I spoke to Salamander, they explicitly stated that NRVs should not be fitted as the tank is vented, and the pumps are universal pumps, therefore maintaining the pressure between pump and mixers.
If I did need to fit them, could they be installed just after the pump, rather than at every mixer? Installing them at the mixers is a no go now since its tiled in

 

[Johntheo5]

Don't know if NRVs are a requirement or not, I was thinking of Xover between the hot&cold but may not be a problem since you don't have a combi supplying the HW. Some shower mixers come with the NRVs already installed?.
The pump already have NRVs, otherwise pressure couldn't be maintained in the pump accumulator,