Single shower pump positive of negative pressure?

[DavidB]

Hi, I need to install a shower pump on the hot water system. The house is a bungalow but with the attic converted in to bedrooms and a bathroom. The cold feed cistern is about 500mm above the bathroom floor and the hot water tank is on the ground floor.
Do I need to fit a positive pressure pump or a negative pressure pump? Is it best to site the pump directly after the hot feed from the hot water tank?

Many thanks
Dave

 

[Ben-gee]

Definitely negative head.
If you want to pump all hot outlets then yes pump sited by the bit water cylinder- better to push water than pull it.

 

[exedon2]

Would agree with that pump suction short as possible we always use a warix flange when pumping all of the hot supply.

 

[rpm]

Pumps of this design do not suck! They are flooded inlet type so best installed as close to the source as possible.

 

[Ben-gee]

Pumps of this design do not suck!

In my opinion they do when made by Salamander!
Much better when custard can afford a nice ST Monsoon.

 

[rpm]

In my opinion they do when made by Salamander!
Much better when custard can afford a nice ST Monsoon.

Does Salamander say this anywhere BG? Genuine Q as it is not something that I am aware of.
A bit rude to call customer such in an open post mate.

 

[DavidB]

Thanks to all who replied, much appreciated.
Cheers
Dave

 

[exedon2]

Just had time to check the fitting instructions for a Stewart Turner universal they clearly described the incoming side as the suction (inlet) pipework .

 

[rpm]

Just had time to check the fitting instructions for a Stewart Turner universal they clearly described the incoming side as the suction (inlet) pipework .

A lot of manufactures use that term. Next time you have time to play place the Inlet hose in a bucket of water set below the pump.

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[John.g]

Don't know if you are all joking or not but a negative head pump has nothing to do with the suction, both positive & negative head pumps need a minimum (positive) head to operate, a negative head pump is needed where the shower head is above the level of the feed tank and there is then no flow to start the pump (via its flow switch) when the shower is turned on. A negative head pump uses a small expansion type pressure vessel so when the shower is switched on the pressure falls and starts the pump via a pressure switch, the flow switch then switches off the pump when the shower is turned off. The pump will then occasionally switch on/off to maintain a minimum pressure.

 

[DavidB]

Don't know if you are all joking or not but a negative head pump has nothing to do with the suction, both positive & negative head pumps need a minimum (positive) head to operate, a negative head pump is needed where the shower head is above the level of the feed tank and there is then no flow to start the pump (via its flow switch) when the shower is turned on. A negative head pump uses a small expansion type pressure vessel so when the shower is switched on the pressure falls and starts the pump via a pressure switch, the flow switch then switches off the pump when the shower is turned off. The pump will then occasionally switch on/off to maintain a minimum pressure.

Fitted the pump, sited it on the hot water outlet right by the tank. Pump works fine, but was pumping out the hot water vent into cold water cistern. I put a push fit cap end on the vent pipe and everything working ok. Do I need to fit a pressure relief valve on the vent pipe? If so what bar relief rating would you reccomend.
Thanks
David

 

[exedon2]

No DO NOT cap or restrict open vent in any circumstances!
Do not use till this problem is rectified
Picture of how you have done pipework required.

 

[DavidB]

No DO NOT cap or restrict open vent in any circumstances!
Do not use till this problem is rectified
Picture of how you have done pipework required.

Pump is connected to hot outlet pipe on hot water tank.

 

[exedon2]

Have you used a flange? Warix or similar? As I said clear pictures required.

 

[John.g]

Shower possibly has no NRVs so hot water back flowing through cold shower supply up through the HW cylinder and then venting into the CWST.

 

[DavidB]

Have you used a flange? Warix or similar? As I said clear pictures required.

Yeah, warix fitted and all ok
Thanks