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Is my cold water pressure too high?


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Recently fitted a Seaflo domestic water pump, the system seems to operate well with no leaks but after taps have been run for a longish time the pump runs on and on and on before switching off.  There’s an accumulator in the system set at 19psi
The spec says the pump has a shut off pressure of 60psi - could the need to build pressure up to what seems pretty high be the cause?

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60 psi seems very high, if you have a calorifier. Typically these have a pressure release valve which opens at around 3.5 bar (52psi) so perhaps the pump is just pumping water through the PRV. You certainly wouldn’t want to put 60psi into a normal calorifier, it will burst fairly quickly.

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50 minutes ago, nicknorman said:

60 psi seems very high, if you have a calorifier. Typically these have a pressure release valve which opens at around 3.5 bar (52psi) so perhaps the pump is just pumping water through the PRV. You certainly wouldn’t want to put 60psi into a normal calorifier, it will burst fairly quickly.

Good thought but on my Surecal the PRV is 4 bar which is c. 60psi.

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Just now, dmr said:

 

So the pressure IS too high because you have zero safety margin.

 

 

It is also WAY too high because you are cycling the calorifier between 0 and 4 bar every time you run a hot tap for any amount of time, and this causes metal fatigue and cracking, i.e. much earlier failure than if the pressure switch was set to say, 2 bar.

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Yes you need to have a ~10psi margin between pump cutout pressure and PRV pressure. Firstly because these things are not very accurately set, and secondly because as Tony says you get pulses of pressure arising from the sudden stoppage of flow when a tap is closed. Once a PRV starts to allow flow, the pressure will have to drop a bit (ie below a nominal 4bar) before it closes off again.

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I am getting the impression that many people think a higher pressure and a higher volume pump is the way to go. Unless you have a very good reason, I don't understand this. As long as the shower is adequate, I doubt you need much over 20PSI unless you have stupid small plumbing. I ran mine at 15psi for years, and some of that was in about3/8" bore plastic. Likewise, a lower output pump would go a long way to reducing cycling because the outlet flow is more likely to be greater than pump delivery.

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24 minutes ago, MtB said:

 

It is also WAY too high because you are cycling the calorifier between 0 and 4 bar every time you run a hot tap for any amount of time, and this causes metal fatigue and cracking, i.e. much earlier failure than if the pressure switch was set to say, 2 bar.

 

To be pedantic its probably from about 4 bar down to just under the cut in pressure of the pump rather than zero.

Here is pressure with a tap running.

My gauge does not even go to 60psi 😀.

 

I expect the working water pressure (during a shower) is dictated by pump flow and pipe resistance etc and that the pressure rating of the pump probably has little influence.

Water Pressure 1.jpeg

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7 minutes ago, Tony Brooks said:

I am getting the impression that many people think a higher pressure and a higher volume pump is the way to go. Unless you have a very good reason, I don't understand this. As long as the shower is adequate, I doubt you need much over 20PSI unless you have stupid small plumbing. I ran mine at 15psi for years, and some of that was in about3/8" bore plastic. Likewise, a lower output pump would go a long way to reducing cycling because the outlet flow is more likely to be greater than pump delivery.

 

I agree. I'm wondering what led the OP to fit the Seaflo pump with 60psi cut off. What make and model was the old pump (which presumably worked satisfactorily for many years)? Changing one component to one of a different specification in any system usually leads to trouble! 

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13 minutes ago, MtB said:

 

I agree. I'm wondering what led the OP to fit the Seaflo pump with 60psi cut off. What make and model was the old pump (which presumably worked satisfactorily for many years)? Changing one component to one of a different specification in any system usually leads to trouble! 

There was no old one, it’s a completely new system. Seaflo, as far as I know, is a Chinese  knock-off of Jabsco. They do a  lot of water and bilge pumps. Why did I pick this one? As many of us do, I just saw something on EBay that looked right and went ‘click’ - I dare say I can fit a Square D pressure switch to sort it (if I can pick the right one of those 🤣). 

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1 minute ago, starman said:

There was no old one, it’s a completely new system. Seaflo, as far as I know, is a Chinese  knock-off of Jabsco. They do a  lot of water and bilge pumps. Why did I pick this one? As many of us do, I just saw something on EBay that looked right and went ‘click’ - I dare say I can fit a Square D pressure switch to sort it (if I can pick the right one of those 🤣). 

Sometimes there is a possibility to adjust the cutout / cut in pressure on pumps. Maybe have a close look for a something that might be an adjuster?

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13 minutes ago, starman said:

There was no old one, it’s a completely new system. Seaflo, as far as I know, is a Chinese  knock-off of Jabsco. They do a  lot of water and bilge pumps. Why did I pick this one? As many of us do, I just saw something on EBay that looked right and went ‘click’ - I dare say I can fit a Square D pressure switch to sort it (if I can pick the right one of those 🤣). 

 

I think Seaflo are a direct copy of Shurflo rather than Jabsco, the mouldings look identical (maybe even from the same production line????) though sometimes in a different colour. This is what can happen when a company moves their production to China. Its the the same with Stanadyne injectors, you can buy an expensive Stanadyne made in China or a cheaper Chinese made in China injector.

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Just now, dmr said:

 

I think Seaflo are a direct copy of Shurflo rather than Jabsco, the mouldings look identical (maybe even from the same production line????) though sometimes in a different colour. This is what can happen when a company moves their production to China. Its the the same with Stanadyne injectors, you can buy an expensive Stanadyne made in China or a cheaper Chinese made in China injector.

Sorry - brain failure; the name should have been a clue!

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5 hours ago, starman said:

Recently fitted a Seaflo domestic water pump, the system seems to operate well with no leaks but after taps have been run for a longish time the pump runs on and on and on before switching off.  There’s an accumulator in the system set at 19psi
The spec says the pump has a shut off pressure of 60psi - could the need to build pressure up to what seems pretty high be the cause?

I have a pump like that and use an external pressure switch at a much lower pressure. I am hoping that being designed for a hirer pressure it will last longer before it starts leaking.

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11 minutes ago, ditchcrawler said:

I have a pump like that and use an external pressure switch at a much lower pressure. I am hoping that being designed for a hirer pressure it will last longer before it starts leaking.

I also have a Seaflo which replaced a failed Seaflo. The component that failed was the pressure switch, which was very cheap looking. I fitted a Square D type pressure switch. On Ebay you can get a fair selection of robust pump control switches where the pressure can be easily adjusted. The one I fitted was factory set at 40 psi, the same as the Seaflo switch, on high with a 20psi cut in. This works well with my Morco which maintains the shower flow and does not cycle constantly.

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5 hours ago, Ex Brummie said:

I also have a Seaflo which replaced a failed Seaflo. The component that failed was the pressure switch, which was very cheap looking. I fitted a Square D type pressure switch. On Ebay you can get a fair selection of robust pump control switches where the pressure can be easily adjusted. The one I fitted was factory set at 40 psi, the same as the Seaflo switch, on high with a 20psi cut in. This works well with my Morco which maintains the shower flow and does not cycle constantly.

Mine runs between 20 and 30 psi. I have a gauge on the system that was sold for a hot tub

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On 02/10/2021 at 09:50, starman said:

Recently fitted a Seaflo domestic water pump, the system seems to operate well with no leaks but after taps have been run for a longish time the pump runs on and on and on before switching off.  There’s an accumulator in the system set at 19psi
The spec says the pump has a shut off pressure of 60psi - could the need to build pressure up to what seems pretty high be the cause?

I have done a semi-permanent fix by discovering a somewhat elderly Sureflo 3901-0213 pump buried in my ‘may be useful’ box. 
It’s certainly cured the lengthy pump running but now the system is rather slow running instead! 
Now the Seaflo is out I’ve also seen it seems to have a pressure adjuster. I’ll have to have a play. 

23898BF5-1635-4F82-8EF8-9766509D73F0.jpeg

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