Converting Positive Head Pump to Negative

[It's me]

I plan to fit a shower pump as we have low water pressure. The flow is about 0.5 litres a minute through the shower head, so is unlikely to be enough to start a positive head pump.

I have read in another thread on here that you can buy add ons for pos.head shower pumps to be able to convert them to neg. head. However, they gave no actual details. Can anyone advise me on this, please? Positive head pumps are so much cheaper than negative head pumps that I would be interested in learning more.

Thank you.

James

 

[muggles]

Salamander made a conversion kit for the CT FORCE range of pumps but have discontinued it. It was about £130. Personally not a fan of Salamander anyway, Stuart Turner are much better. Not aware of any others that could be converted.

 

[ETAF]

I plan to fit a shower pump as we have low water pressure.

how big is your hot water tank, when i looked into this, my water tank was nothing like big enough for a pump , need to be about 225L 50 gallons - mine was a lot less than that 115L as its a combined cold & hot tank in a loft of a bungalow.

Just thought i would mention it, just in case

 

[Johntheo5]

I plan to fit a shower pump as we have low water pressure. The flow is about 0.5 litres a minute through the shower head, so is unlikely to be enough to start a positive head pump.

I have read in another thread on here that you can buy add ons for pos.head shower pumps to be able to convert them to neg. head. However, they gave no actual details. Can anyone advise me on this, please? Positive head pumps are so much cheaper than negative head pumps that I would be interested in learning more.

Thank you.

James

Not the perfect solution but you could probably wire in a "manual" start button to bypass (and in parallel with) the flow switche(s) until the pump starts, you could probably get a mechanical (or digital) type timer switch that stays on for say 30 secs to allow time to get the shower flow established, start button then deenergises and the flow switches will then continue to keep the pump running and then stop it once showering completed.

 

[It's me]

Salamander made a conversion kit for the CT FORCE range of pumps but have discontinued it. It was about £130. Personally not a fan of Salamander anyway, Stuart Turner are much better. Not aware of any others that could be converted.

That is a shame. Thank you.

how big is your hot water tank, when i looked into this, my water tank was nothing like big enough for a pump , need to be about 225L 50 gallons - mine was a lot less than that 115L as its a combined cold & hot tank in a loft of a bungalow.

Just thought i would mention it, just in case

It is a little small. It coped with the old power shower, supplying three consecutive showers. However, it is in need of replacement and I plan to fit a larger tank.

Not the perfect solution but you could probably wire in a "manual" start button to bypass (and in parallel with) the flow switche(s) until the pump starts, you could probably get a mechanical (or digital) type timer switch that stays on for say 30 secs to allow time to get the shower flow established, start button then deenergises and the flow switches will then continue to keep the pump running and then stop it once showering completed.

This is the sort of thing that I envisaged, but I can just imagine my wife's response to the idea. I suspect that I shall just have to bite the bullet and buy a new negative head pump.

James.

 

[Madrab]

There were 2 types, one that was a little pump that would provide just enough pressure to activate the flow switch(es). The other was just a remote power switch.

With most pumps, you can just wire in a manual power switch to turn the pump on. Most pumps prime themselves (spin up) when the power is turned on, so have a manual FCU powering the shower. Turning on the shower then turning the pump's power on is usually enough to kick start it, once it starts flowing it will keep running, then turning off the shower should shut the pump down as usual. You could probably also use a pull cord switch.

Not sure if that's the same as what @Johntheo5 suggested.

 

[It's me]

There were 2 types, one that was a little pump that would provide just enough pressure to activate the flow switch(es). The other was just a remote power switch.

With most pumps, you can just wire in a manual power switch to turn the pump on. Most pumps prime themselves (spin up) when the power is turned on, so have a manual FCU powering the shower. Turning on the shower then turning the pump's power on is usually enough to kick start it, once it starts flowing it will keep running, then turning off the shower should shut the pump down as usual. You could probably also use a pull cord switch.

Not sure if that's the same as what @Johntheo5 suggested.

Thank you for the explanation and for the suggestion. On balance, I shall be done with it and buy a new negative head pump. I had an informative call with Salamander and it seems that the CT80bu will be a good solution, especially with the restricted space that I have.

James.

 

[Johntheo5]

I see thats a regenerative type pump which Salmander themselves say are noisier than the centrifugal type but are more tolerant of any entrained air, you might enquire about the noise aspect.

 

[It's me]

I see thats a regenerative type pump which Salmander themselves say are noisier than the centrifugal type but are more tolerant of any entrained air, you might enquire about the noise aspect.

That is a good point and Salamander did mention that the CT Force 30 is quieter, but that it is also larger. The space on the airing cupboard floor is very limited and I am not sure yet whether the quieter one will fit. I shall need to do some careful measuring.

 

[ColesIrl]

A positive pressure pump typically requires at least 50cm of head difference between the water surface of the header tank and the highest water within the pipework before the shower head.

If the pump is fitted and not working, try lower the shower hose and head to the level of the mixer and see if the pump will now trigger normally. It might simply be that in order to trigger the pump you need to lower the shower hose and head. If that doesn't work, the simplest option is to replace the pump with a negative head version.

If you know that the pump will operate if the hose is drained, but it isn't practical to do it each time, It might be possible to install an automatic drain down valve after the mixer so that the required head difference is created automatically each time after use.

A simple system that might work would be an "anti-stagnation drain down valve" that can be fitted to the shower hose at the mixer. This drains down the shower hose after use, and it should create sufficient pressure difference to trigger the positive pressure pump. An example of this product is the Aquatools AT880.

In certain circumstances where the mixer and pipework is concealed it might work to install a brass automatic drain valve (eg 1/2" VOZ-IRRITROL 204201). This valve has a spring inside it that opens in order to drain the water from the pipe and then closes again under pressure from the pump, but the real drawback from this system is that the water from this valve will have to be drained to a wastewater trap. If you are considering this option it is probably marginally better to just get a negative pressure pump.

Hope that helps somebody.

 

[Madrab]

A positive pressure pump ............

FYI - As per the forum rules, old threads wouldn't normally be resurrected as it can be confusing about who's answering what. Also worth nothing that the OP hasn't been on for 8 months so chances are it's all sorted.

Do appreciate it is sound advice tho.

 

[muggles]

A positive pressure pump typically requires at least 50cm of head difference between the water surface of the header tank and the highest water within the pipework before the shower head.

If the pump is fitted and not working, try lower the shower hose and head to the level of the mixer and see if the pump will now trigger normally. It might simply be that in order to trigger the pump you need to lower the shower hose and head. If that doesn't work, the simplest option is to replace the pump with a negative head version.

If you know that the pump will operate if the hose is drained, but it isn't practical to do it each time, It might be possible to install an automatic drain down valve after the mixer so that the required head difference is created automatically each time after use.

A simple system that might work would be an "anti-stagnation drain down valve" that can be fitted to the shower hose at the mixer. This drains down the shower hose after use, and it should create sufficient pressure difference to trigger the positive pressure pump. An example of this product is the Aquatools AT880.

In certain circumstances where the mixer and pipework is concealed it might work to install a brass automatic drain valve (eg 1/2" VOZ-IRRITROL 204201). This valve has a spring inside it that opens in order to drain the water from the pipe and then closes again under pressure from the pump, but the real drawback from this system is that the water from this valve will have to be drained to a wastewater trap. If you are considering this option it is probably marginally better to just get a negative pressure pump.

Hope that helps somebody.

This thread is nearly 3 years old, and this post looks a lot like advertising...

 

[ColesIrl]

It's not advertising. It's a solution to a problem that I've given a lot of thought to. Maybe this isn't the forum for me.