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Adjusting the PRV to go to 4 bar..?

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Discuss Adjusting the PRV to go to 4 bar..? in the Plumbing Jobs | The Job-board area at PlumbersForums.net

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dblvkrb

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We've installed a new 25mm water mains in to replace a led mains in and the pressure is so high we've had to put pressure reducing valve on and cap at 3 bar.

The flowrate from the tap is about 10 litres per minute but we're expecting at least 15l/m. The taps/showers are rated to 3bar but I want to find out if anyone thinks there is a great risk in adjusting the PRV to 4bar to increase the flow.

For info, the combi storage boiler is rated for 18l/m and the current Plumbing has been power flushed, no issues. Any advice appreciated?
 
dblvkrb said:
We've installed a new 25mm water mains in to replace a led mains in and the pressure is so high we've had to put pressure reducing valve on and cap at 3 bar.

The flowrate from the tap is about 10 litres per minute but we're expecting at least 15l/m. The taps/showers are rated to 3bar but I want to find out if anyone thinks there is a great risk in adjusting the PRV to 4bar to increase the flow.

For info, the combi storage boiler is rated for 18l/m and the current Plumbing has been power flushed, no issues. Any advice appreciated?
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No never , you might well be creating a pressurised bomb
Combi set ups operate at 1.5 bar
And no more ever. There have been accidents ! With over over pressurised unvented systems
I know it’s my specialist area
Centralheatking
 
Would advise speaking to local water board to see what pressure and LPM you could possibly expect in your road then if that is ok look at the pipework to and from the boiler
 
When the new mains in was originally plumbed without the PRV the water was bouncing out of the sink, so it must be related to the flow to some degree. I absolutely agree about potentially creating a time bomb.

Let me ask this a different way, what flow would you expect on average with good pressure and a high spec combi, what other things can I do to improve the flow rate from the shower or taps?
 
As we’ve said though flow and pressure are different. Alright ignore pressure ask the water board what you should expect. If you are a way off that it’s time to start testing.
Is the strainer filter on the prv blocked?
If you rig up a tap or pipe straight after the stopcock what do you get then flow wise??
What does the incoming reduce to after the stopcock, 25-??
 
The water bouncing out the sink shouldn't have been affected by installing a pressure reducer as technically these restrict standing pressure, not working pressure (or at least thats my understanding of them). Basically the standing pressure of your system will be exactly the same as before you installed your new water main so you don't have anything to worry about regarding tap rating etc. I'd turn your pressure reducer up to max, then run the tap and slowly turn the valve down until you achieve your desired flow rate.
 
dblvkrb said:
When the new mains in was originally plumbed without the PRV the water was bouncing out of the sink, so it must be related to the flow to some degree. I absolutely agree about potentially creating a time bomb.

Let me ask this a different way, what flow would you expect on average with good pressure and a high spec combi, what other things can I do to improve the flow rate from the shower or taps?
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Off the stop tap to the prv what size pipe

Also what size is the prv 15mm

Pipe size off the prv to the boiler ?
 
Craig Watson said:
The water bouncing out the sink shouldn't have been affected by installing a pressure reducer as technically these restrict standing pressure, not working pressure (or at least thats my understanding of them). Basically the standing pressure of your system will be exactly the same as before you installed your new water main so you don't have anything to worry about regarding tap rating etc. I'd turn your pressure reducer up to max, then run the tap and slowly turn the valve down until you achieve your desired flow rate.
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PRV doesn’t affect flow
 
Riley said:
PRV doesn’t affect flow
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That's what I thought too but op installed a new water main, had too great a flow rate, installed a prv and now flow isn't so great. If turning the prv up increases his flow to what he classes as desirable then it's an easy fix
 
I’m not sure I get your point. If incoming is 3 bar and prv is set to 3 bar then 3bar give or take will pass through it
 
Craig Watson said:
That's what I thought too but op installed a new water main, had too great a flow rate, installed a prv and now flow isn't so great. If turning the prv up increases his flow to what he classes as desirable then it's an easy fix
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That's pressure
Craig Watson said:
How can you be so sure? What if op's working pressure is 3 bar and the pressure reducer is set at 3 bar?
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Prv don't adjust flow just pressure

Just because it's not splashing all over the place at reduced doesn't mean it's not the same flow just less pressure
 
Flow is impacted by correct pipe sizing, obstruction or restriction in the pipework and can also be controlled by reduced lpm sanitaryware
 
As Riley and others have said pressure and flow are not the same thing. A PRV could have sorted out the splashing tap but will not have affected flow.

As an example:

If we have two taps both with a flow rate of 15 lpm where tap no1 has 6bar pressure and tap no2 has 3 bar pressure, both will fill the sink up in the same amount of time. But when taps are turned on tap no1 will splash much more violently off the surface of the sink due to the much greater pressure than tap no2. i.e. its the same amount of water but coming out with more force, turn the pressure down and water hits the sink with less force so doesn't splash/bounce but its exact same amount of water per minute hitting the sink.
 
Riley said:
Flow is impacted by correct pipe sizing, obstruction or restriction in the pipework and can also be controlled by reduced lpm sanitaryware
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Yes I know that, and I'm not trying to argue with you about the difference of flow and pressure.
Read op's post, he says after installing a new water main, his flow was that good that water was bouncing out the sink. So to correct this, he installed a pressure reducer (I know this technically shouldn't change anything). Since installing the pressure reducer, his flow rate has dropped, again I know this technically shouldn't happen, but if he has a high working pressure it could be interfering the pressure reducers function. Basically if the pressure reducer is set to 3 bar and his working pressure is 3 bar or slightly higher then the valve may be opening and closing repeatedly as the pressure required by the prv will be constantly achieved. Sorry if that sounds confusing, in my head I know what I mean, it's just hard writing it :confused:
 
I would be looking for an obstruction clearly something has changed but it won’t be the PRV purpose that has caused it
 
to be honest it could be something as simple as some muck from the new mains install getting trapped in the new PRV and affecting flow
 
Riley said:
As we’ve said though flow and pressure are different. Alright ignore pressure ask the water board what you should expect. If you are a way off that it’s time to start testing.
Is the strainer filter on the prv blocked?
If you rig up a tap or pipe straight after the stopcock what do you get then flow wise??
What does the incoming reduce to after the stopcock, 25-??
Click to expand...

The PRV is brand new, is it likely the filter would already be blocked? I haven't experimented with running a tap straight off the mains stopcock but it's a good idea.

After the stopcock it reduces to 10-11 l/m, up to 12l/m if running purely off of the cold mains.
 
dblvkrb said:
The PRV is brand new, is it likely the filter would already be blocked? I haven't experimented with running a tap straight off the mains stopcock but it's a good idea.

After the stopcock it reduces to 10-11 l/m, up to 12l/m if running purely off of the cold mains.
Click to expand...

any pics of the install?
 
Craig Watson said:
The water bouncing out the sink shouldn't have been affected by installing a pressure reducer as technically these restrict standing pressure, not working pressure (or at least thats my understanding of them). Basically the standing pressure of your system will be exactly the same as before you installed your new water main so you don't have anything to worry about regarding tap rating etc. I'd turn your pressure reducer up to max, then run the tap and slowly turn the valve down until you achieve your desired flow rate.
Click to expand...

Well this is exactly my point, thank you! I've heard "pressure and flow are not the same things" about a hundred times, and I understand they are definitely not directly related, but you can't deny the flow was way too high if anything before installing the PRV.

Do you not think it would be risky to simply turn the valve down (increasing the pressure) until I have 15l/m? I know plenty of people who "overclock" their systems and don't have any issues for years, but then I've heard the other kind of story where it all goes wrong..
 
dblvkrb said:
15mm for both - the distance from the stopcock to the boiler is maybe 3/4 metres.
Click to expand...

you sure its not a 20mm main ?

what make of prv are you using
 
You will not increase the flow by increasing the pressure. If that’s what you’re intent on doing you might as well remove the PRV. The PRV could be defective. In terms of what does it reduce to I meant what pipesize is it coming out of the stopcock. Do you notice this reduced flow at all outlets
 
Riley said:
You will not increase the flow by increasing the pressure. If that’s what you’re intent on doing you might as well remove the PRV. The PRV could be defective. In terms of what does it reduce to I meant what pipesize is it coming out of the stopcock. Do you notice this reduced flow at all outlets
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15mm coming off the stopcock - the flow rate is the same on the 1st floor and in the loft conversion, almost no loss the further up the house you go.

It might be a defective PRV - would this definitely not reduce the flow rate if it were working effectively?
 
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