Positive or Negative shower pump.. whats the difference..

[rakvara]

Hi,

Apologies if this has been posted before, im still unsure..
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As the subject suggest, I need help in purchasing a shower pump. I already have one installed, a Salamander ESP 80 CPV, however, this is a pump, which distinguishes automatically whether the supply is positive or negative. This pump has broken down, out of warranty, and a new one needed! im looking to buy a stuart turner monsoon, as i have heard these are very good in quality.. however, im unsure whether i need a positive one or a negative one.

Here are the details..

2 floor house.. cold water storage tank in the kind of in the attic.. the current pump (in a utility closet - based on the 2nd floor), is located just beneath it (about 1 metre below), with 1 bathroom, to the side of it... and a shower unit on the first floor. The pump is for cold water flow.

Question is.. is this positive or negative flow? im not a plumber, just an average joe.. trying to get the damn shower unit working again... lol! please try and provide non-technical answers.. as they will just confuse me... and prob lead to more questions.. lol!

Thank you in advance...

 

[Richard C]

Think I'll leave this one to you Technotim, you know what your about & me balls are still aching from the last effort

 

[HERTS P&D]

When shower head is below cold water tank by at least 1metre = Postive Head

When shower head is above the cold water tank then a Negative pump is needed. (Eg loft conversion)

Andy

 

[Technotim]

LOL Come on Richard I am a massive fan you not only give good sound advice you also tell people how to parent at the same time!!!

I will keep it as simple as poss.

it is not really all about height its about flow, if you water flows at 1 liter per minute then you can use a positive head pump, these are flow switch operated and will turn on at about 0.6 liters per minute.

If you are not sure then always buy negative head which are pressure switch operated and sense a pressure drop to activate.

 

[picasso]

or just fit a universal

http://www.bathrooms365.com/acatalog/Stuart_Turner_Monsoon_Universal_2.0_Bar_Twin_Shower_Pump.html

 

[Richard C]

I just wrote this drawn out drivel off line but on going to post, I can see youve already beaten me to it; I'll post it for posterity anyway

Got to trip in here; it’s not what you’ve said is wrong but some pumps are happy with 0.5m whilst others specify 0.6m or more. The positive/negative pump choice is also dictated by the position of the shower head & the pipes feeding it relative to the CWS tank. But what’s’ really important is a minimum, un-pumped flow of 1 litre/min at the shower head; this is required on practically all pumps to trip the flow switches & start the pump; if you can’t guarantee this, fit a negative head pump.

 

[Technotim]

or just fit a universal

http://www.bathrooms365.com/acatalo...iversal_2.0_Bar_Twin_Shower_Pump.html[/QUOTE]

An ESP80 is a single impeller pump not twin?

Its a good pump dunno why it has not lasted for you are you sure it is fitted correctly.
Its the same motor as the Stuart Turners!

 

[picasso]

your right but I kinda wonder what kind of shower the op has got that only needs a pumped cold water supply, if he is going to the trouble of installing a pump why not put is a twin?

the universal is also available as a single

 

[Technotim]

I just wrote this drawn out drivel off line but on going to post, I can see youve already beaten me to it; I'll post it for posterity anyway

Got to trip in here; it’s not what you’ve said is wrong but some pumps are happy with 0.5m whilst others specify 0.6m or more. The positive/negative pump choice is also dictated by the position of the shower head & the pipes feeding it relative to the CWS tank. But what’s’ really important is a minimum, un-pumped flow of 1 litre/min at the shower head; this is required on practically all pumps to trip the flow switches & start the pump; if you can’t guarantee this, fit a negative head pump.

See Richard good to see your confidence has come back!

The issue always is posters needing help have to give all the correct information and they have to want to listen.
Richard can you pm me as I do not know how to do it as I want you too look at something for me.

 

[Technotim]

your right but I kinda wonder what kind of shower the op has got that only needs a pumped cold water supply, if he is going to the trouble of installing a pump why not put is a twin?

the universal is also available as a single

It could be an electric in that case pump should be neg head and maybe ST better choice as they have a smaller one which would be better as electric showers have a low flow rate, or some people have pump from cold on combi systems to effect the flow of the combi less by slowing the refill rate on the cws tank.

 

[rakvara]

Cheers for the replies all!

in terms of why i dont have a twin pump fitted, im not entirely sure! the plumber did originally fir a twin pump, but the said that it was not need due to the force of the hot water?

so instead, he fitted a single pump, just for the cold water! to be honest, it was working fine, gave excellent pressure, just sometimes it had to be reset, again not sure of the reason! it finally gave way about 3 months ago, and i havent got round to sorting it out since! a friend of mine did take it apart, and said that the motor had gone, and as its out of warranty, they wont take a look at it!

when it was working, the computer led system on top, did have the negative light on.. im assuming that this meant that it was negative..


so is it safe to say, that both negative and positive would work on my system? but if unsure.. go negative??

Once again.. thanks for the help!

 

[Technotim]

Sorry mate, something is wrong here!

Are you storing hot water in a cylinder?

 

[rakvara]

nope! only cold water is stored in a tank, which is situated in the attic!

i do find it a slightly wierd set up, more so, as i dont really understand it myself... but it did work.. and the flow of the water was a a very good rate, when the pump was working!

im a swaying more to the negative head, only because, i cant guarantee the 0.6 litre per min flow rate needed for the positive head?!? and due to it providing water to the bathroom to the side of it aswell.. i think it would make more sense, as this the taps are slightly higher than the pump itself!

i hope that makes sense.. lol!

 

[Technotim]

The taps being higher than the pump will not make any difference.

But I think you are best going for a neg head pump as well.

 

[ajrobb]

I am confused do you have an electric shower or a combination boiler?

I am curious why you don't use mains cold water if you get hot from a combi?