Positive pumps and shower mixers

[tjpicnic]

I have a positive shower pump that works well with current gravity system and shower mixer. I want to replace shower and found a mixer valve I like on Victoria Plumbing- But the info on most of their shower valves states ‘Please note a positive pump will not work’ under any circumstances? and if so why? Their help line has no one who knows the answer.

 

[John.g]

It may be that the flow through this mixer isn't enough to start a positive head pump which probably requires > 1.5LPM to activate the flow switch to start the pump whereas a negative head pump doesn't rely on the flow switch to start, it starts on a pressure switch so even a dribble of water will suffice?.

 

[tjpicnic]

It may be that the flow through this mixer isn't enough to start a positive head pump which probably requires > 1.5LPM to activate the flow switch to start the pump whereas a negative head pump doesn't rely on the flow switch to start, it starts on a pressure switch so even a dribble of water will suffice?.

 

[tjpicnic]

Maybe that’s it but as I said most of Victoria Plumbing mixers say the same thing. Cant see the same warning on other suppliers’ websites. Does VP use same manufacturer for all its large range and they all have the same limitation or are they just playing safe cos too many people are trying to use their showers with positive pumps in negative head situations. Why are positive pumps still made if they can’t be used with most shower valves🤷‍♂️Wish I understood.

 

[Timmy D]

I’m sure they had a load of complaints that various of their mixers didn’t work on positive or were incorrectly installed, so someone decided it was better to put out a blanket statement.

Anyways, don’t but from them. You’ll likely regret it in a couple of years when you need parts and they don’t have them.

 

[John.g]

Maybe that’s it but as I said most of Victoria Plumbing mixers say the same thing. Cant see the same warning on other suppliers’ websites. Does VP use same manufacturer for all its large range and they all have the same limitation or are they just playing safe cos too many people are trying to use their showers with positive pumps in negative head situations. Why are positive pumps still made if they can’t be used with most shower valves🤷‍♂️Wish I understood.

Stuart Turner state that a flowrate of 1LPM is required to enable reliable positive pump starting.
I have had showers in several houses where I had to take the shower head&hose out of the holder and put it on the ground to start the pump, its not much fun trying to take a fixed shower head down to get the pump going.

 

[Jeff50]

Plumber's Assistant
Pearl Wilson, Plumber's Assistant

Welcome! How can I help with your plumbing question?
I need to replace a Triton T450i pump. It is located in a loft above an electric shower which is gravity fed from a water tank in the main house (around 2.5 meters above). It has a pull cord for the power supply. Can I do a straight swap with a single impeller positive head pump?