Use shower pump for whole house

[Newhome91]

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:

Salamander 2.0 Bar Twin Positive Head Shower Pump CT75 x Tra

Salamander Pumps' CT75+ Xtra pump is a hard-working affordable pump. Robust, compact and quiet, this pump is the ideal way to boost the water pressure to a single shower. This product is a twin impeller shower pump, suitable for boosting both hot and cold water in positive head, gravity fed...

www.cityplumbing.co.uk

Thanks, hope this makes sense!

 

[steadyon]

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.

 

[Newhome91]

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.

 

[rpm]

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)

 

[Newhome91]

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

 

[king of pipes]

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

 

[Ric2013]

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.

 

[John.g]

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.

 

[rpm]

Grundfos do whole house continuously rated brass bodied pumps but don't know how they deal with running one end against a closed head.

Perhaps with an inbuilt PRV?

 

[John.g]

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.

 

[Ric2013]

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?

 

[John.g]

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.

 

[SimonG]

Why would the water get hotter and hotter?

Physics. Is it Boyles law?