Plumbing.. psi/bar question

[pquinn]

Hello folks,

 

Just wondering what would be the outcome if i were to change from a 2 bar/30 psi water pump to a 1 bar/15 psi if both pumps claim to have a flow rate of 12 ltrs per minute bearing in mind that i know little of plumbing. Any answers appreciated, Paul.

[Paul C]

You'd need to adjust your accumulator, but basically simple answer is: there's not much difference pragmatically. The only time there would be a difference is if you were pumping significantly long distances, thin pipes or upstairs, where pressure drop would play a significant factor. Basically, the pump, when a tap is open, is pumping at its max rate against not very much pressure because the tap is open (to atmosphere).

 

Where is the pump in relation to the shower, bathroom sink and kitchen sink? 1 or 2 bathrooms on the boat? Anything else using water apart from the 3 items mentioned?

[Tiggs]

Assuming this is for a narrowboat water system, I would expect very little difference. If you have a separate pressure sensor switch then that would need resetting, as would the accumulator tank, if you have one. You might find your shower is a little less harsh.

Edited April 5, 2016 by Tiggs

[RLWP]

Your shower will be rubbish

 

Richard

[nb Innisfree]

Innisfree has a 16 psi pump and the shower is OK.

[RLWP]

Innisfree has a 16 psi pump and the shower is OK.

 

Yes, and you didn't experience the 30psi shower first

 

It will be a very noticeable difference

 

Richard

[nicknorman]

The flow rate out of taps and shower will be much less since the flow is dependant on the pressure vs restrictions from pipes and taps.

[nb Innisfree]

 

Yes, and you didn't experience the 30psi shower first

 

It will be a very noticeable difference

 

Richard

True but it wasn't 'rubbish'!, in fact it was very good. We had two 16psi pumps, (two separate tanks) one was twice the distance from the bathroom than than the other but there was no noticeable difference in delivery between the two.

[Paul C]

This is why I asked for details on the distances involved. Also, the pipework diameter and number of bends will have an influence. Our pump is located in the bathroom so all the pipe runs are short and logical. Hence, the pressure (on ours at least) isn't that important but the main difference is the flowrate (we upgraded to a higher flowrate pump).

[RLWP]

True but it wasn't 'rubbish'!, in fact it was very good. We had two 16psi pumps, (two separate tanks) one was twice the distance from the bathroom than than the other but there was no noticeable difference in delivery between the two.

 

I agree, I suspect our pump runs at that pressure. And if you halved your pump pressure, how would that be?

 

Richard

[alan_fincher]

I'm with Richard on this.

 

Assuming you are talking about the cut out pressure of the pump in both instances, then I think if you halve it and connect it to the same pipework you will notice a very considerable reduction in performance.

[raymondh]

I have just changed from pumping at 30psi tp 40psi @15ltrs pm and the difference is amazing, shower is 100% better washer fills in less time and there is no noticeable loss of flow when using more than one outlet

 

Down side we now use more water

 

Ray

[pquinn]

pump to kitchen tap approx. 5 feet, 1 bend,

pump to shower tap approx. 13 feet, 2 bends

pump to bathroom tap approx 17 feet, 2 bends

pump to toilet approx 21 feet, 2 bends.

 

15 mm pipes.

 

no acumulator tank.

Edited April 5, 2016 by pquinn

[Ex Brummie]

Have just done the same as Ray, and as he says, the difference is tremendous, particularly in shower performance. yes, it does use more water, but with a 250 gallon tank, it's not a big problem.

I think halving your pressure will be detrimental. Do you have a calorifier or a multipoint?

[pquinn]

Have just done the same as Ray, and as he says, the difference is tremendous, particularly in shower performance. yes, it does use more water, but with a 250 gallon tank, it's not a big problem.

I think halving your pressure will be detrimental. Do you have a calorifier or a multipoint?

I have a calorifier.

[Paul C]

pump to kitchen tap approx. 5 feet, 1 bend,

pump to shower tap approx. 13 feet, 2 bends

pump to bathroom tap approx 17 feet, 2 bends

pump to toilet approx 21 feet, 2 bends.

 

15 mm pipes.

 

no acumulator tank.

 

Those are quite long, I guess the pump is next to the water tank at the front of the boat - in which case I'd stick with a 30psi pump.

http://www.pipeflowcalculations.net/pressuredrop.xhtmlthis calculator suggests ~2.5psi pressure drop

[nb Innisfree]

 

I agree, I suspect our pump runs at that pressure. And if you halved your pump pressure, how would that be?

 

Richard

Our taps are/were a bit marginal but shower great, strange that, I would have thought it would have been the other way round. 30 psi would be great for the taps though.

[nb Innisfree]

Apologies to OP and RLWP, Innisfree pump pressure is 26 psi not 16 psi. so as RLWP says shower would be rubbish, crap even.

 

Doh!

 

Memory's staring to get a bit iffy, I blame my age (69 in a few days time)

[pquinn]

Alright folks, thanks for the replys. It seems the general consensus is to stick with the 30 psi.So i think i will to be on the safe side. cheers.

[Ex Brummie]

A calorifier adds significantly to the pipework resistance, particularly if your pump is at the front, and your calorifier is at the back. There is a lag between the delivery from your hot tap registering with your pump pressure switch which shows as a period of low flow. At 16 psi, this will be more noticeable.