Hot Water Circulation Pump Recommendation !

[Monkey Wrench]

Can anyone please recommend an "in line" circulation pump to improve hot water pressure in a house.

The pump will be required to provide hot water to four outlets only, (bath tap, sink tap and two basin taps). It's a gravity fed system and the pressure to the four hot water outlets is quite poor.
The taps are all modern with 15mm flexi hose supply and reduced bore inlets (M10 & M12).

There's not sufficient room in the airing cupboard for a single impeller floor mounted pump and so an in-line pump would be preferred. I've been looking at the Grundfos 15/90 but the technical specs seem to imply that the pump is suitable for one outlet only (fitted under sink) rather than in an airing cupboard to supply multiple outlets.

Any recommendations would be appreciated.

Thank You

 

[dancinplumba]

what about under the bath ?

 

[Monkey Wrench]

Thanks for the post dancinplumba.

The bath is on the otherside of the room to the airing cupboard and it's a tiled floor so there is no way of accessing or
modifying the pipework for a pump mounted under the bath.

 

[dancinplumba]

you could perhaps try a negative head pump high up, maybe in the attic ?

 

[PlumbBobBob]

doesn't necessarily need to be negative head as long as it is below the cwsc

 

[Monkey Wrench]

Thanks for the posts.

If sited in the loft, the pump would have to be negative head as there's no way of of getting it below the CWST.

The price is also a consideration as I can't find a negative head single impeller head pump for less than £245 which, coupled with other materials and installation cost, is going to be expensive.

 

[Guest123]

Stuart Turner single impellor pumps every time for me.

 

[PlumbBobBob]

Thanks for the posts.

If sited in the loft, the pump would have to be negative head as there's no way of of getting it below the CWST.

The price is also a consideration as I can't find a negative head single impeller head pump for less than £245 which, coupled with other materials and installation cost, is going to be expensive.

is the cwst not on a platform? even an inch below would make it positive head imho

 

[Monkey Wrench]

is the cwst not on a platform? even an inch below would make it positive head imho

I'm not 100% certain about that so will check tomorrow.

Thanks for the posts.

 

[PlumbBobBob]

there should be a platform to spread out the weight of the tanks over several joists and preferably a supporting wall

 

[ecowarm]

Thanks for the posts.

If sited in the loft, the pump would have to be negative head as there's no way of of getting it below the CWST.

The price is also a consideration as I can't find a negative head single impeller head pump for less than £245 which, coupled with other materials and installation cost, is going to be expensive.

A negative head pump still has to go lower than the cistern and prefably at side of cylinder it is the outlet that can be higher than the cistern ie shower head.

 

[Monkey Wrench]

there should be a platform to spread out the weight of the tanks over several joists and preferably a supporting wall

I seem to remember that its a 50 gallon coffin tank (I installed it about four years ago) mounted directly onto board over joists which do indeed pass over a supporting wall directly under the tank.

It's an old three storey Victorian house but I don't remember enough about the configurtion of the loft to know weather a positive or negative pum would be required so will check tomorrow.

Thanks again.

 

[Monkey Wrench]

I've checked the loft and the tank does indeed sit on 18mm plywood mounted directly over the loft beams and a supporting wall. Any pump install in
the loft would therefore mean the pump sitting at the same height as the bottom of the tank.

I'm still interested to know if anyone has had any experience with the Grundfos 15/90 ?

 

[Roger Welton]

If space really is such an issue then I would just bite the bullet and get an unvented cylinder fitted (provided mains flow / pressure is up to it).

If grundfos say that pump is only suitable for one outlet then I'm sure they are right, no direct experience though.

 

[Monkey Wrench]

If space really is such an issue then I would just bite the bullet and get an unvented cylinder fitted (provided mains flow / pressure is up to it).

If grundfos say that pump is only suitable for one outlet then I'm sure they are right, no direct experience though.

Thanks for the response Roger Welton but replacing the whole hot water system is definitely way out of budget !

 

[glenno1]

Can you raise cwsc

 

[Monkey Wrench]

Can you raise cwsc

Thanks for the post glenno1.

The CWST is a 1650x460x475 coffin tank so its going to take quite a lot of work to build a suitable platform to rais it a few feet. Additionally, there is limited access
to the loft and limited headroom (hence the coffin tank) so raising the tank is not really an option.