Shower Pump Question

[harbinger31]

We've recently moved into a house which we bought and renovated, adding a new bathroom downstairs. The cold water supply throughout the house comes directly off the mains, and the hot water is fed from a tank in the loft. The original upstairs bathroom is fine, with all 3/4" plumbing and low pressure fittings. The new bathroom basin and shower are both rated at 2 bar, however, and this causes a problem. There is not enough hot water pressure, so the mixer is pushing cold water back up the hot water pipe. If I flush the toilet and turn on the cold tap on the hand basin, then I can have a shower, but this is clearly not a permanent solution, and I'd like to add a pump to boost the hot water pressure.

The environment: Cold water is delivering at around 2bar (have yet to measure it). Hot water pressure is at roughly 4 meters, so should be delivering at around 0.4 bar. Cold water supply is slow (~30l/min), is there is a chance that the header tank can run dry. Also, I'd far prefer it if I can mount the pump in the airing cupboard, after the cylinder and overflow pipe, than have to rip the ceiling out of the new bathroom. So I'm looking for a pump as follows:

- Can deliver 1.5 to 2 bar of pressure (from a positive head of 0.2-0.3 bar)
- Has an auto-shutoff if it runs dry (in case the bath/shower empties the header tank)
- Can operate up to 80 degrees C
- Single port - I only want to boost hot water. Cold water is routed separately.
- Rated for a good solid shower (25-35l/min), but that won't be damaged if there isn't any back pressure (the bath upstairs fills very quickly through the 3/4" pipes)
- Isn't more expensive than either ripping out the ceiling to fit a pump for only the shower, or replacing the fittings on the shower and hand basin to low-pressure friendly ones.

Any input would be appreciated.

Thanks,
Peter

 

[Plumbstar Tom]

okay,
you can use a single impeller pump for this but it is never ideal as it will pump at a constant 1.5bar and your mains is subject to change and vary. It may still work and I have indeed seen it work for years. The airing cupboard is the ideal site for a shower pump by the way
The ideal solution is dedicated hot and cold gravity fed feeds to the pump and then to the shower. In both cases it should like you need to increase your cold water storage cistern size.
I don't know of an auto shut off pump
Why on earth are you operating at 80°??? that is dangerous!

I know you probably don't want to hear this but it sounds like it might be worth a plumber popping round and giving you your options and costs.

 

[rpm]

25-35L/min ? Gonna need a big tank or take very quick showers.

 

[harbinger31]

okay,
you can use a single impeller pump for this but it is never ideal as it will pump at a constant 1.5bar and your mains is subject to change and vary. It may still work and I have indeed seen it work for years. The airing cupboard is the ideal site for a shower pump by the way
The ideal solution is dedicated hot and cold gravity fed feeds to the pump and then to the shower. In both cases it should like you need to increase your cold water storage cistern size.
I don't know of an auto shut off pump
Why on earth are you operating at 80°??? that is dangerous!

I know you probably don't want to hear this but it sounds like it might be worth a plumber popping round and giving you your options and costs.

Thanks Tom. I was hoping to avoid yet another callout, but I think getting the plumber in is going to be the most prudent call. Then at least I can discuss all possible options and weigh them up.

Thanks
Peter