Negative or positive pump head, Surrey Flange and more > Advice please

[Stevie h]

Hi Guys , please bear with me if some of my terminology is incorrect

I'm fitting a power shower for a friend , the set up is

vented heating system with hot water cylinder in cupboard on landing

tank in loft on a platform , ( about waist height)

plan that is underway is -

fit a surrey flange ( :innocent ) to top of the cylinder , loop pipe work to the base of cylinder ( anti gravity loop) before going straight up to the pump , pump is situated on the loft floor below water tank .. all in 22mm

drill plastic loft tank , fit 22 tank coupling and take 22mm cold to pump, fit gate valves , then out to showers

am i correct in thinking that a POSITIVE HEAD pump is OK for the job in hand? , is the anti gravity loop OK to prevent air locks?

Friend wants pump in loft not in the airing cupboard

any advice welcome

I'm off to a find a surrey flange

Cheers

Ste

 

[m4tty]

The job I was on last week is exactly the same situation as you are in and he used a negative head pump and it didn't work. He wanted to move pump next to cylinder but client wanted it in loft so he's had to buy a kit for

 

[NozSpark]

I did a shower pump with a plumber friend,, first off he fitted it in the loft, header tank was similar to yours... there was not enough head for the pump to switch on so he had to move it to the floor of the floor below, even then you had to open the valve in a very quick motion for it to work.

Other pumps that I have been a part to installing have never run off a surrey flange or their own cold feed from the tank and have worked perfectly, they have however all had at least 8' of head...

IMHO I think the loop of pipework is a pointless waste (I stand to be corrected though)

 

[Sidewinder]

PLEASE don't use gate valves unless you have to, they can be unreliable in domestic water!!!

Use full bore ball lever valves if possible.

 

[sparky b]

Use a Salamander ESP Pump, it will decide for itself if it wants to run on positive or negative head, they also make an 's flange' to go in the top of the cylinder which eliminates air in the system and will allow you to keep the existing expansion pipe and tee off to the pump.

 

[Chr!s]

You need to make sure the pump is correctly sized

Make sure your cistern is big enough

Make sure you mount the pump correctly to lessen noise.

am i correct in thinking that a POSITIVE HEAD pump is OK for the job in hand? , is the anti gravity loop OK to prevent air locks?

Sounds like a positive system, gravity loop is there basically for air and heat.

A lot depends upon the type of pump, heres a link for one type, some need a certain level of head pressure.

http://www.screwfix.com/sfd/i/cat/pdfs/26/p3248426.pdf

 

[kme]

As plumber says; header tank sizing can be a big problem; especially with twin impeller pumps of 3 bar and above...........dont forget that you`re effectively drawing BOTH hot & cold from the header tank; if it empties you`ll create airlocks.

I have, in the past, used an electromagnet from a doorbell to trigger the reed switch on the pump - your other option could be to raise the header tank as high as possible in the loft?????

KME

 

[Andy™]

I have, in the past, used an electromagnet from a doorbell to trigger the reed switch on the pump

KME

i used an air switch a few times. no electrics needed to be taken to the bathroom