Installing a shower pump

[andyste]

I'm about to replace the shower in a downstairs bathroom, and fit a pump too. I've had a couple of plumbers out for quotes and both have said there should be a dedicated hot feed for the shower all the way from the hot water tank upstairs. Currently the shower hot comes off a pipe in the bathroom feeding the bath & sink. This hot is 22mm all the way from the tank. Any idea why the plumbers would suggest having a separate feed? Is it to stop the shower from going cold if someone turns on a hot tap elsewhere? If left as it is, will having a pump cause a problem if someone was to turn on another tap?

One of the plumbers also said the shower's cold should come from the tank in the loft, even though the shower already has a dedicated cold tank above this d/stairs bathroom. Any idea why he said this?

Finally, anything else to bear in mind regarding the plumbing, as we've never had a shower pump before? I've heard that it is necessary to fit some kind of valve to the top of the hot water tank. What would that be for?

Thanks in advance
Andy

 

[rjm2k]

Yes it should have its own feed from the hot, taken from an essex flange (side of tank) or a salamander flange (top of tank), this stops air getting into the flow and making noise/damaging the pump. It is normal for the pump to also have its own cold feed, why they can't use this dedicated tank I'm not sure but it could be down to its size (not big enough to supply a pump for very long) or vertical position relative to the pump (effects of gravity etc).

All of these things (dedicated feed from a flange, dedicated cold) etc are the ideal and what's needed to satisfy most pump guarantees, you could get away without all of it but could cause issues/invalidate the guarantee. Make sure they place it on some foam and a small concrete slab if you want it to be really quiet, there's a good video on youtube if you search for shower pump, it's near silent with the airing cupboard door shut.

One other thing to remember is to check that your plug hole can cope with such a large amount of water so quick.

If you want to look into instalation details download the instructions for a pump from somewhere like salamander and it will give you an idea of what's needed and why.

 

[longdogs]

You can buy pumps that don't require any special flange and are just teed into the hot water pipe which comes out of the top of the cylinder.

 

[warmadmax]

You can buy pumps that don't require any special flange and are just teed into the hot water pipe which comes out of the top of the cylinder.

most still require this to be a dedicated feed to the pump, whether its tee'd or flanged,
imagine if you open a tap upstream of the pump, it will more than likely draw air through the tap rather than the tap running with water out of it...

 

[tincup]

Hi

"One of the plumbers also said the shower's cold should come from the tank in the loft, even though the shower already has a dedicated cold tank above this d/stairs bathroom. Any idea why he said this?"

If the pump is to be sited at the foot of the hot water cylinder the water from this source would be considered at positive head. The cold source if below the pump would be negative head and likely to draw air into the pump, damaging its bearings.

 

[kvsalamander]

Hi

"One of the plumbers also said the shower's cold should come from the tank in the loft, even though the shower already has a dedicated cold tank above this d/stairs bathroom. Any idea why he said this?"

If the pump is to be sited at the foot of the hot water cylinder the water from this source would be considered at positive head. The cold source if below the pump would be negative head and likely to draw air into the pump, damaging its bearings.

All domestic shower pumps would need to be below the cold water cistern to ensure they are constantly flood with water during use to prevent cavitation on the impellers. Negative or positive head would be determined where the highest point in the pipework is after the pump/the shower head (whichever is higher) to the bottom of the cold water tank. Usually the distance between the two would be around 600mm. So as long as there is around 600mm or more from the bottom of cold tank to the highest point of the system this would ensure there is enough natural flow to lift the flow switches in the pump and turn it on. If you cant get this natural flow you would need to go for a negative head pump that works on a pressure drop rather than a flow rate.

hope this clarifies

cheers