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Hi all,

We have a gravity fed system and are getting a new shower installed as part of a whole new bathroom fit out.

It's been suggested we could connect our bathroom sink taps to the mains, rather than the water storage tank as it is at present.

Is there any reason why a shower pump can't be used as a whole house pump? I think if we just have the taps connected to the mains we won't be able to blend the hot/cold as the mixer tap is intended to be used.

We have this one:


Thanks, hope this makes sense!
 
1. Ordinary twin pumps expect to pump hot and cold, and its the fluid which lubricates the internals. This is fine on a shower, where you are nearly always mixing hot and cold. Its not so good if you are using taps, which may have only hot OR cold flowing. One side of the pump goes without lubrication. Whole house pumps are designed to cope with this.
2. You can't connect hot taps to the mains. You can get mains pressure hot, but this requires either a combi boiler, and unvented hot water system, or a pump on the hot water supply.
3. If you mean to connect only the cold taps to the mains, then, as you say, you will have unequal pressures and endless trouble using mixer taps / showers.
4. Note that pumps MUST have their own supplies from both the cold water storage cistern and the hot water cylinder. They cannot be connected to existing pipe work.
 
1. Ordinary twin pumps expect to pump hot and cold, and its the fluid which lubricates the internals. This is fine on a shower, where you are nearly always mixing hot and cold. Its not so good if you are using taps, which may have only hot OR cold flowing. One side of the pump goes without lubrication. Whole house pumps are designed to cope with this.
2. You can't connect hot taps to the mains. You can get mains pressure hot, but this requires either a combi boiler, and unvented hot water system, or a pump on the hot water supply.
3. If you mean to connect only the cold taps to the mains, then, as you say, you will have unequal pressures and endless trouble using mixer taps / showers.
4. Note that pumps MUST have their own supplies from both the cold water storage cistern and the hot water cylinder. They cannot be connected to existing pipe work.


That's useful, thanks very much. I think the theory was to try to bypass the cold water storage to get better quality water. Sounds like it's best to leave it as it is currently. The tap we're installing is a standard basin mixer tap.
 
1. Ordinary twin pumps expect to pump hot and cold, and its the fluid which lubricates the internals. This is fine on a shower, where you are nearly always mixing hot and cold. Its not so good if you are using taps, which may have only hot OR cold flowing. One side of the pump goes without lubrication.
Bottom line is no it wont work properly, shower pumps will only pump so far then the pressure drops off - A lot.

Re opening one tap (say hot), these pumps have one common shaft rotating two impellers so one end is feeding the open tap the other impeller is pressurising against a dead end which will very quickly cause damage.

(However as long as there is water in the chamber it is lubricated)
 
Bottom line is no it wont work properly, shower pumps will only pump so far then the pressure drops off - A lot.

Re opening one tap (say hot), these pumps have one common shaft rotating two impellers so one end is feeding the open tap the other impeller is pressurising against a dead end which will very quickly cause damage.

(However as long as there is water in the chamber it is lubricated)

Great, thank you very much 😊
 
As the guys above have stated this would be difficult to achieve a shower pump is designed specifically for that reason, to supply hot and cold water from a tanked supply at a boosted rate and not to supply the whole property. Regards kop
 
To address your question: no, that pump isn't suitable. You could, however, look into having a 'whole house' pump fitted. These are a little more expensive, but not massively more expensive and could be used to boost all your hot water.

An issue others have alluded to is that the shower ought to have its own independent run from the pump to the shower (and the pump must have its own independent connection to the cylinder) otherwise pressures will fluctuate if other taps are opened.

If your taps are mains pressure cold, with pumped hot, that might just work, though from a pressure point of view it would be better to have both pumped from storage. But if you are pumping the hot, you certainly need to increase the pressure on the cold in some way as pumped hot/gravity cold would not be a good idea.
 
Grundfos do whole house continuously rated brass bodied pumps but don't know how they deal with running one end against a closed head, especially the hot end, also most of these manufacturers stipulate that the hot water temperature shouldn't exceed 60c or 65C, not sure which.
 
The problem with closed head running is temperature rise so a inbuilt PRV would just recirculate the water which would get hotter and hotter, if the pump has brass impellers as well and if the pump seals are high temperature design and if the pump has dry running protection then maybe that's their answer as a 2 bar pump will have to reach 135C before the water starts vaporising.
 
The problem with closed head running is temperature rise so a inbuilt PRV would just recirculate the water which would get hotter and hotter, if the pump has brass impellers as well and if the pump seals are high temperature design and if the pump has dry running protection then maybe that's their answer as a 2 bar pump will have to reach 135C before the water starts vaporising.
Why would the water get hotter and hotter?
 
Because all or most of the pump power required at that closed head is converted into heat as the pump efficiency is very low, probably only a few %, if it were (impossibly) still 100% then there would be no heat rise. The efficiencies of very large industrial pumps is often checked/monitored by actually measuring this temperature rise during normal operation.
 
Because all or most of the pump power required at that closed head is converted into heat as the pump efficiency is very low, probably only a few %, if it were (impossibly) still 100% then there would be no heat rise. The efficiencies of very large industrial pumps is often checked/monitored by actually measuring this temperature rise during normal operation.
Yes. The friction and motion will degrade to heat. Surely the solution would be to run the water through a loop of pipe (or uninsulated section of the pump body) such that as the heat rises the heat losses would eventually equal the heat gain and no further increase in temperature would result? Which is presumably something the pump manufacturers have achieved if they say their pumps can be run against a closed head?
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Physics. Is it Boyles law?
No, that's to do with the pressure and volume of a gas. And, yes I did look that up.
 
It would be interesting to run one of these pumps with say the hot side pumping only and then just feel the cold pump and also along the pipe as the pipe is open for some of its length at least and will absorb and dissipate heat along here.
 
Maybe we should stick to Boils law!

P1V1/T1 = P2V2/T2 is a combination of Boyle's & Charle's law but don't think this much help in choosing a whole house pump, personally, I don't think installing one of these pumps will cause it any real damage as long as its not feeding a outside tap and you are watering the lawn for a long period.
 
Why would the water get hotter and hotter?
The water having nowhere to go and the increased pressure raises the temperature is the short answer. There would be a world of difference in the design of a shower pump compared to the design of a whole house pump. A quick look at the sizes and prices tells a story.
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personally, I don't think installing one of these pumps will cause it any real damage as long as its not feeding a outside tap and you are watering the lawn for a long period.
Thermal cuts outs, are they fitted to expensive versions?
 
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Perhaps with an inbuilt PRV?

Salamander seem to employ a form of PRV alright, in the form of a by pass tube.

"" The technology behind Salamander’s shower pumps
Pumps, explains the technology inside the products that helps to make them powerful, quiet and compact…

Crossover technology

Salamander’s crossover technology allows its pumps to boost both hot and cold water at the same time, or independently of each other. In situations where a thermostatic shower is running, both hot and cold water will be supplied to the shower. However, as the pump only has one common driveshaft, if only a hot or cold tap is used, both sets of impellers would be turning but only one side of the pump would be supplying water, meaning one side of the pump would be running ‘closed head’. This causes an increase in temperature and pressure in that side of the pump, leading to severe damage.

However, most Salamander pumps have an innovatively placed bypass tube found in bathroom, universal and whole house variants, which allows the excess pressure to be relieved into the open side of the pump, which also brings fresh water into the closed head chamber, stopping the pump from overheating ""
 
Maybe we should stick to Boils law!

P1V1/T1 = P2V2/T2 is a combination of Boyle's & Charle's law but don't think this much help in choosing a whole house pump, personally, I don't think installing one of these pumps will cause it any real damage as long as its not feeding a outside tap and you are watering the lawn for a long period.

The seals will go on the non used/less used side. Seen it a handful of times.
 
I'd like to see how that Salamander crossover tube technology works.
Stuart Turner give a 5 year warranty on their Monsoon which isn't bad even when used for whole house use bearing in mind all the above, wonder if they use anything to prevent seal failure etc for closed head conditions.
 
Salamander seem to employ a form of PRV alright, in the form of a by pass tube.

"" The technology behind Salamander’s shower pumps
Pumps, explains the technology inside the products that helps to make them powerful, quiet and compact…

Crossover technology

Salamander’s crossover technology allows its pumps to boost both hot and cold water at the same time, or independently of each other. In situations where a thermostatic shower is running, both hot and cold water will be supplied to the shower. However, as the pump only has one common driveshaft, if only a hot or cold tap is used, both sets of impellers would be turning but only one side of the pump would be supplying water, meaning one side of the pump would be running ‘closed head’. This causes an increase in temperature and pressure in that side of the pump, leading to severe damage.

However, most Salamander pumps have an innovatively placed bypass tube found in bathroom, universal and whole house variants, which allows the excess pressure to be relieved into the open side of the pump, which also brings fresh water into the closed head chamber, stopping the pump from overheating ""
Could you add a link to where you found this John. It makes interesting reading and like you I would like more intel on this cross over tube.
TIA
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The seals will go on the non used/less used side. Seen it a handful of times.
Are we talking rubber lip seals or proper mechanical seals Simon.l
 
Could you add a link to where you found this John. It makes interesting reading and like you I would like more intel on this cross over tube.
TIA
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Are we talking rubber lip seals or proper mechanical seals Simon.l

Could you add a link to where you found this John. It makes interesting reading and like you I would like more intel on this cross over tube.
TIA
[automerge]1603014282[/automerge]

Are we talking rubber lip seals or proper mechanical seals Simon.l

The Grundfos Monsoon has a mechanical seal (see data Sheet)and gives a 5 year warranty, the Salamander, a 3 year, don't know about the seal.
 

Attachments

  • Monsoon-Standard-Twin-DS.pdf
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  • Salamander CT Range Brochure March 2017.pdf
    9 MB · Views: 4
Are we talking rubber lip seals or proper mechanical seals Simon.l

Rubber lip seals.

All the ones I have seen have been on salamander domestic units.

Had a body burst on the cheaper stuart turner models as well.
 
With the pump running with a closed head and because of the check valves then there must be a potential for very excessive pressures due to expansion of the trapped water which is getting hotter.

Maybe no check valve on pump inlet though.
 

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