shower pump installation

[grippa]

I have read some really informative threads about shower pump installation and was wondering if there is any other solution to using flanges (surrey, essex etc) for my situation.
I want to raise the pressure of the water flow in the main bathroom shower to about 1.5 to 2 bar (maybe even a 1 bar would do (a twin shower with drench head and handset fed from a diverter bar). The bathroom shower head is about 3m+ to 4m below the bottom of the cold storage tank and about 1m+ to 2m below the top of the hot tank. The pump will obviously be lower under the bath. Due to the way that the house is constructed (the bathroom has its own floor midway between the first floor and the ground floor and is not very near to the hot tank cupboard), getting a dedicated hot feed to the bathroom shower is not an easy one to do as pipes would have to be on show or a lot of the dry-lined walls would have to be severely messed up along with the tiling (bathroom is fully tiled and replacement matching tiles cannot be sourced).
So....is there anyway of protecting the pump from sucking in air from the hot tank vent or to somehow 'vent' any air under the bath (it does not sound good I know). I do not want a 'general' pump as it will kick in whenever any hot/cold tap is used (including toilets).
There are two other showers in the house, on their own separate cold feeds from the main cold tank, that will not be pumped.
Will I get away with just installing the pump? (I realise the probs of dry running a pump).
Many thanks for any help

 

[ChrisR]

Will I get away with just installing the pump?

Yes, if the flow rate's low enough. At some point you'll start to suck air. Depends on pipe lengths and resistances.
So I'd try with a small pump, but not a plastic-bodies one like a Salamander, they love to leak if the supply isn't ideal. Stuart Turner all brass one would stand a much better chance. More dosh.

Or use a whole house variable speed pump. More £ but at low flows they're very quiet.

 

[grippa]

Many thanks Chris, I really appreciate your input..
I had thought about a whole house pump but as the site for the installation would be in the airing cupboard which is next to the main bedroom and all walls are stud/drylined, the sound that the pump would make would be an issue. When you talk of low flow not being too noisy when using a whole house pump, would a bath, washing machine, another shower or a a toilet flushing be a higher flow demand and therefore more pump speed and therefore more noise?

I was also thinking of a good solid shower pump , brass etc, but as the design of shower said that 2 bar was the preference, would the fact that the shower head already has about 3-4m distance below the storage tank allow a 1.5 bar to be used or even a 1 bar pump? This would then mean that the pump would draw less and maybe not get the air problem so much?
I had also looked at the low voltage pumps as a solution to where it will be sited but am not sure if they will be brass etc

 

[dumbrill]

Many thanks Chris, I really appreciate your input..
I had thought about a whole house pump but as the site for the installation would be in the airing cupboard which is next to the main bedroom and all walls are stud/drylined, the sound that the pump would make would be an issue. When you talk of low flow not being too noisy when using a whole house pump, would a bath, washing machine, another shower or a a toilet flushing be a higher flow demand and therefore more pump speed and therefore more noise?

I was also thinking of a good solid shower pump , brass etc, but as the design of shower said that 2 bar was the preference, would the fact that the shower head already has about 3-4m distance below the storage tank allow a 1.5 bar to be used or even a 1 bar pump? This would then mean that the pump would draw less and maybe not get the air problem so much?
I had also looked at the low voltage pumps as a solution to where it will be sited but am not sure if they will be brass etc

The pump won't ever draw air unless you run the cold water tank dry and start to empty the hot water tank. This might happen if the mains doesn't fill up the tank at the rate the pump is pumping at, but it would have to be a long shower. The concern you're grappling with is cavitation. You need to maintain a minimum pressure into the pump inlet to make sure it pumps OK. Otherwise it will be noisy, have a short life or stop pumping.

You want to run the pipes from the cold and hot water tanks in a way that will reduce any losses, ie. minimum bends, large bore, essex flange, short distance. You can't connect a pump that's going to deliver a meaningful flow into the hot and cold water pipes in the bathroom. It has to have it's own supply from tanks so that the head losses into the suction are minimised.