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Positive or Negative shower pump.. whats the difference..
- Thread starter rakvara
- Start date
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I am about to install a shower pump. My bathroom ceiling is 2.15m high and I will have a coffin CWS immediately above the shower. There is likely to be a head of 500-700mm at the shower head.
For short pipe runs, what is the minimum recommended head above a shower to trigger a positive head pump?
For short pipe runs, what is the minimum recommended head above a shower to trigger a positive head pump?
Can not really answer that as it depends on how restrictive the shower valve head or hose and handset is, if the items are for use on a low pressure system then you might get away with a positive head pump.
You have two choices as far as I can see, either buy a negative head pump and it will work, or install equipment and do a flow test, Unless the manufacturer or retailer gives you the flow rate of the equipment @ 0.05bar.
You have two choices as far as I can see, either buy a negative head pump and it will work, or install equipment and do a flow test, Unless the manufacturer or retailer gives you the flow rate of the equipment @ 0.05bar.
I am confused
I am curious why you don't use mains cold water if you get hot from a combi?
its difficult to explain my set up, purely because, one i dont understand it totally myself, and two, the set up has changed a little while ago!
basically we had two seperate boilers, one purely for my bathroom downstairs, and the other, which used to be used for central heating and providing water kitchen and upstairs bathroom! we then got it renovated, and the boiler for the downstairs bathroom was removed. so now we have one combi that provide c.heating around the house and hot water to 2 bathrooms and kitchen. in the course of which a pump was added to make up the flow for the shower that was put in.
the water goes from the cold water storage tank, into the pump, and then around the house. the pump was only for the cold water, not the hot water!
all very confusing, and like i said before, not totally sure if its correct, but it worked, till the pump broke down!
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If you no longer have a hot water cylinder, I don't see why you'd want to keep the cold water storage tank and pump. Unless you have mains water supply problems, combination boiler set ups do without a CWS and use cold from the mains.
If you still have a HWC and a CWS for bath taps, I suspect you could still get rid of your pump and substitute mains cold water for the shower and basin. Old CWS ought not be used for potable water (basin and sink cold taps). Current by-laws seal the CWS against infestation (my parents had a birds' nest fall into their old CWS).
If you still have a HWC and a CWS for bath taps, I suspect you could still get rid of your pump and substitute mains cold water for the shower and basin. Old CWS ought not be used for potable water (basin and sink cold taps). Current by-laws seal the CWS against infestation (my parents had a birds' nest fall into their old CWS).
Sounds to me that you do not have great mains pressure at the top of the house, I would stick with what you have as it worked if you get a pump with a slightly different pressure you might not be able to balance the temperature on the shower very well.
A couple of notes.
The pump might have broke down if it was not at least 600mm from the bottom of the cws, and check that the tank is at least 50 gallons, also you need to make sure the the flow into the cws is restricted so as not to have to greater effect on the hot pressure.
One of the other reasons from using the neg head pump is that when you are opposing mains pressure they tend to work better as they already have the pressure between the pump and the shower so will activate straight away.
If you get one from us they are normally delivered next day allowing for snow etc.
http://www.salamander-pumps.com/esp-80-cpv-single-pump.html
A couple of notes.
The pump might have broke down if it was not at least 600mm from the bottom of the cws, and check that the tank is at least 50 gallons, also you need to make sure the the flow into the cws is restricted so as not to have to greater effect on the hot pressure.
One of the other reasons from using the neg head pump is that when you are opposing mains pressure they tend to work better as they already have the pressure between the pump and the shower so will activate straight away.
If you get one from us they are normally delivered next day allowing for snow etc.
http://www.salamander-pumps.com/esp-80-cpv-single-pump.html
Hello, I have just installed what I thought was top of the range £300 Salamander pump for my bathroom with a mixer shower, mixer tap and toilet. The plumbing is simple, so I am sure there is nothing odd going on there, but the pump seems allow the hot water to flow into the cold water plumbing. So after a few minute of no water use, the cold water is very hot. Only once its been running for about a minute will cold water come out of the cold side again. I am certain that its inside the actual pump that this "leak" happens. What is wrong with the installation? I am guessing that the central hot water pressure is higher than the cold water, which is why if there is a water connection inside, the pressure pushes back the cold water. Do I need to replace this pump? Will one with negative head work?
Perhaps related, the pump also sometime is left running after taps are all closed.
Thanks for any thoughts!
- Toffe
Perhaps related, the pump also sometime is left running after taps are all closed.
Thanks for any thoughts!
- Toffe
Hi,
Some Salamander pumps have bypass fitted which allows the water to pass from hot to cold and vice versa, this is only meant to happen to eleviate the pressure build up in the impellers when only one side is used.
There should be a non return valve or in fact two sets of non return valves in the pump itself.
For this to happen something is wrong with these, I would recommend you give salamander a call 0191 516 2002
Tim
Some Salamander pumps have bypass fitted which allows the water to pass from hot to cold and vice versa, this is only meant to happen to eleviate the pressure build up in the impellers when only one side is used.
There should be a non return valve or in fact two sets of non return valves in the pump itself.
For this to happen something is wrong with these, I would recommend you give salamander a call 0191 516 2002
Tim
They are on the outlet side of the water section not the electronics area.
If you have just installed it I don't think you should be stripping it down, if it's new.
In fact you have worried me that you are looking in that section for the non return valve
Tim
If you have just installed it I don't think you should be stripping it down, if it's new.
In fact you have worried me that you are looking in that section for the non return valve
Tim
Tim, I just peeked under the hood at the electrics. I was actually looking for any adjustments, i.e. for the second problem I have, which is that the pump doesn't always stop when the taps are all closed. This one could be related to the internal bleeding.
Obviously the valves wouldn't be with the electronics!
My theory is still that the completely calcified pipes means that hot water has a higher pressure than cold causing both issues. It does say in the manual that the hotwater pressure should be "equal" to the cold water, i.e. ventilated.
If I am forced to replace this positive head with a negative head, should I go with Grundfos Watermill Amazon? Is there a reason NOT to over spec to 4bar version (apart from price, noise, size). I just want a GREAT shower - priceless.
Obviously the valves wouldn't be with the electronics!
My theory is still that the completely calcified pipes means that hot water has a higher pressure than cold causing both issues. It does say in the manual that the hotwater pressure should be "equal" to the cold water, i.e. ventilated.
If I am forced to replace this positive head with a negative head, should I go with Grundfos Watermill Amazon? Is there a reason NOT to over spec to 4bar version (apart from price, noise, size). I just want a GREAT shower - priceless.
Tim, thanks for the idea - non-return on the hot is indeed a simple solution, not sure why I didn't think of it.
The model is RHP75 twin:
http://salamanderpumps.co.uk/pumps/right-range/rhp75
- K
The model is RHP75 twin:
http://salamanderpumps.co.uk/pumps/right-range/rhp75
- K
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