Grundfos UPA 15 90 Booster Pump

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Hi There,

In my bathroom I have installed a bath/shower mixer tap with a chrome rigid riser going upto a wall mounted shower head. The tap was billed as a low pressure tap (0.2 bar) and while I knew the shower pressure wouldn't be immense I was expecting a fairly usable shower.

Problem is despite the loft tank being c2.5 metres above the bath, the hot water pressure is insufficient to prevent the mixer tap from diverting the flow back to the bath when you are trying to use the shower (diverter button on tap drops back down). This applies even when attaching a temporary shower head and using it at the level of the taps rather than the shower riser height. I can hold the button up and get an ok flow but obviously that is not practical.

After a bit of googling I have discovered the Grundfos UPA 15 90 Booster Pump with flow switch. This claims to boost pressure by 0.5 to 0.75 bar which sounds ideal as it should be sufficient for my needs and for c£100 should see me through until the boiler is replaced with a combi somewhere down the line.

My question is can this pump be simply installed with adjacent isolating valves alongside the hot cylinder as per the attached sketch without causing water to be pumped back up the overflow pipe or are there other pipework modifications required?



Any help greatly appreciated. Many thanks in advance.
 
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Thanks for the help kevplumb and jackthom.

Note this is a mixer tap on my bath not a separate shower mixer in the wall. All cold water in my house is at mains pressure the tank in the loft feeds the hot water cylinder only.

The installation is intended to boost hot water pressure throughout the house not a separate shower therefore how would I install the surrey flange when I only have 1 pipe running from my hot water cylinder?

Can you clarify for me?
 
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Without the flange there's a slight danger the pump will draw in air from the overflow vent so, if you want the whole house hot supply to go via the pump, the top of the surrey flange should lead only to the vent pipe, while the side connector would go to the pump etc.

It is a bit unusual for the bath cold tap to be fed from mains directly so I would double check that it isn't teed off the header tank cold feed near the entrance to the DHW cylinder.
 
Thanks jackthom.

Pretty sure that the bath cold tap is not fed from the loft tank (the pipework under the bathroom floor also has the toilet and basin on the same cold pipe as the bath and is 15mm not 22mm like the hot pipe for the bath). All the same I'll check it out when I get home.

Is there not a risk that if the top of the flange goes straight to the vent and no water is supplied from that connection that whole pipe will be full of air which will still get through despite the flange. I far as I can ascertain the typical use of a surrey flange is where one output supplies the rest of the house with a vent and the other output supplies a shower pump only.

Is there not a similar fitting I could attach in line with the pump (below the T on the right hand side of my sketch) so that it is below the top of the cylinder and full of water?

Alternatively can I not just install the pump in the feed from the cold tank to the hot water cylinder thereby removing the complication of the nearby vent?

Thanks
 
Is there not a risk that if the top of the flange goes straight to the vent and no water is supplied from that connection that whole pipe will be full of air which will still get through despite the flange.


Thanks

That's also a no. :)

The vent will fill with water right up to the level of the header tank regardless.
 
in a word no

it will only pump the water out of the open vent

doh! but if I sat in the tank I could have a cold bath and warm shower at the same time i suppose! :oops:

thanks kevplump for the diagram of surrey flange, making a bit more sense now.

so to sum up is the best approach to install the surrey flange with it's top connection going straight to the vent and the side connection feeding the pump onwards to the taps as per revised sketch below?

if yes I assume that any excess water/pressure in the pumped section can return to the cylinder once the pump stops and would then overflow to the cold tank if necessary
 
Yes that looks like the way to do it.

When the pump stops the pressure will simply fall right back to the normal head pressure through the pump impeller. There won't be any measurable reverse flow back to the cylinder.
 
thanks jackthom

as an update i have now checked and the cold supply to the bath is definately direct from the mains, visually the header tank supplies the hot water cylinder only. as a double check the supply to the bath cannot be from a tank as it stops immediately when the main stopcock under the kitchen sink is closed.

just need to pluck up the courage to do the work now. I take it the surrey flange is the only viable option and i cant just maintain the current configuration and install an auto air vent above the pump to do the same job and minimise the work required?
 

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