What are the Differences Between Positive and Negative Head Systems? | Salamander Pumps

Watch this video to find out the differences between positive and negative head, and why this is important when selecting the right shower pump.
Visit the Salamander eSchool to complete further training - salamandereschool.co.uk/
A positive head system occurs when there is more than 600mm from the bottom of the cold water tank to highest point in the system. A negative head system occurs when the distance from the bottom of the cold water tank to the highest point in the system is less than 600mm.
For advice before, during or after installation give our technical team a call on 0191 516 2002.

[@richardfarrell6872]

Good explanation in the comments thanks. Our pipe work is up and over in the loft. Discovered yesterday that we need a negative pump. When the shower was installed 5 years ago the plumber had used a positive instead of a negative!!

[@SalamanderPumps]

Thanks Richard, hope you're able to enjoy your shower now!

[@maff909]

if i take it apart and short the sensor connections so it runs constantly, can i use it as an external pump for a pond?

[@SalamanderPumps]

Unfortunately, we don't produce pumps for ponds and we can't guarantee that a modified pump would work.

[@11982463]

I still dont get the difference in negative and positive head. All the difference i noticed is the negative pump has an extra part on top

[@SalamanderPumps]

Hi Ricky, to summarise what the video is saying - A system is positive head if there is more than 600mm between the base of the cold water storage tank and the highest point in the system or if there is 2 litres per min natural flow of mixed hot and cold water, in these systems a positive head pump will be activated by the flow. Negative head systems occur when there is 600mm or less between the base of the cold water storage tank, or if there is less than 2 litres per min natural flow of mixed hot and cold water (very little or no natural flow) - this isn't enough flow to activate a positive head pump, so a negative head pump is needed. The negative head pump will be activated by a drop in pressure when an outlet is opened. Let us know if you have any other questions!

[@simonstones1918]

Salamander Pumps well explain, thanks! Funny how it’s bottom of the CWST and not the top, which is where head of pressure which is where it is usually taken ...

[@Mathewmartialart]

@@SalamanderPumps so if the water tank is in the loft , the pump is 8ft below and the shower is another 8ft below that, it would need to have a postiive pump?

[@SalamanderPumps]

@@Mathewmartialart Yeah that's right - unless any other point in the system, such as up and over pipework, goes within 600mm of the base of the cold water tank. Let us know if you have any other questions.

[@smatheson666]

@@SalamanderPumps so I think the difference is to start a positive pressure pump you need water flow, this happens when there is a head, with negative there is no head, so the way these pups work is the pressure Versal, when the shower is open, the pressure is released, this create the flow doe the pump to start, therefore the position of the pump can be anywhere, have I got this correct ?