Expensive upgrade of incoming mains-worth it?

[Agile]

Assuming the prv is in the house then the supply pipe is always at 6 bar ( less the pressure lose caused by the flow!

There is one feature missing from what you are telling us and that is the pressure before and after the prv.

Tony

 

[indus]

Assuming the prv is in the house then the supply pipe is always at 6 bar ( less the pressure lose caused by the flow!

There is one feature missing from what you are telling us and that is the pressure before and after the prv.

Tony

Hi Tony

Would the pressure I measure at the garden tap be the same as the pressure after the prv?

Thanks

 

[Agile]

That all depends on where the prv is fitted.

Probably the garden tap is after it.

You need to measure the maximum flow from other taps before the pressure starts to drop off.

You can easily check where that tap is fitted by seeing if altering the prv changes the pressure there.

Tony

 

[indus]

That all depends on where the prv is fitted.

Probably the garden tap is after it.

You need to measure the maximum flow from other taps before the pressure starts to drop off.

You can easily check where that tap is fitted by seeing if altering the prv changes the pressure there.

Tony

Hi Tony

Though I can't see where the garden tap comes off the main if I vary the prv then the garden tap varies exactly the same. This would mean that the garden tap MUST be after the prv.

And I have no idea how I would measure the pressure before the prv!!

 

[Agile]

That is where it needs to be measured to reach a decision on upgrading the incoming mains supply pipe.

It will need some connection fitted so that a pressure gauge can be added. But there may well already be some fittings connected before the prv but only you can look at that!

Tony

 

[Weedrip]

You also need to ask yourself why the PRV is there in the first place.

Would altering the pressure setting potentially damage any installed devices that have required the PRV to be set at 3bar.

Just winding the pressure up to 6bar could prove catastrophic, possibly requiring the services of a water undertaker!!!! [very amusing Charnwood ]

 

[Agile]

Most taps, showers etc work far better at 3 Bar.

The prv also means a shower will work consistently when other outlets are opened.

It also reduces the chance of flexible hoses bursting.

Tony

 

[indus]

Guys,

I have no intention of turning the prv up to 6bar!! The only reason I mentioned that the mains pressure can go up to 6bar was in case it changed the advice you gave me.

Just to be clear, I'm trying to figure out what improved flow I would get at 3ish bar with 32mm piping, NOT the flow I'd get at 6 bar.

Tony you've said I need to measure the pressure before the prv to establish whether upgrading the mains would be worthwhile. What exactly do you mean? Why does the pressure before the prv make such a difference to the issue given we know we can get decent pressure after the prv?

Thanks for your help

 

[Agile]

The prv will provide ( if it was perfect ! ) unlimited flow at a pressure of 3 bar.

Even if the prv was perfect then in your application its flow would still be limited to the maximum flow rate from the supply that would give 3 bar at the INLET to the prv.

Its that which you dont know and is needed to be known to decide if an upgraded supply pipe is needed.

Tony

 

[indus]

Sorry to be so dense but that still makes no sense to me.

We know the pressure after the prv can be turned up to 6 bar, so that means the pressure at the inlet must be 6 bar. It can't be any less, I suppose it may be a little more as the prv only adjusts up to 6 bar.

Isn't that enough information to figure out what effect upgrading the mains would have?

Thanks again

 

[Weedrip]

First off I don't really understand what Agile is on...

Put simply flow through a pipe is based on velocity x bore, [for the pedants yes I know there's more to it but lets accept the premise for the sake of simple explanation.]

The deciding factor in your case is the bore of the PRV, its ability to pass water at a given volume at 3bar down stream is finite, providing you have in excess of 3 bar plus resistance losses through the PRV up stream.

You say you have 6bar but you have not measured it, if I understand correctly. you do not know what the bore of the incoming mains supply is.
You mention a 22mm dia but fail to say what the pipe is. Is this after the PRV or before? depending on the material will depend the true bore of the incoming main. if its the incoming main then an approx. 22mm dia pipe could have a less than 1/2" bore. if its barrel then after 60 or so years it could be considerably smaller bore.

You should understand that 32mm MDPE main whilst it has a larger bore at only 26mm in bore size it is not that much different than say a 22mm copper pipe, but yes it larger.

you need to know the size of the PRV and its flow characteristics at 3bar output to know if it is suitable for your purpose. only the manufacturers can give you that information. The flow through a ½” PRV set at 3bar will be less than the flow through a 1” PRV set at the same output pressure, irrespective of the incoming mains provided it is in excess of the output by more than a small margin.

A further complication is that the PRV will control the output at the installed point of the PRV , the height of you property and the point at which water is delivered are remote so 3bar @ the PRV will not translate to 3bar three stores up.

So you see the question is easy, but the answer will depend on a lot more information than you have provided.

As a general principle the routing of the mains to as close a point of delivery before you drop / control the output pressure is probably the better solution, but it may also not be the best!

To be honest before you part with your hard earned you would be better off getting a qualified plumber who can see your situation first hand and interpret from knowledge and experience.

I hope that does not sound condescending as its not meant to be.
Good luck

 

[Agile]

I a, surprised that Weedrip does not understand what I am trying to explain although I do appreciate that I was explaining it with correct but not quite so easy to understand language for non professionals.

I was hoping that someone would have explained your situation is simple language.

Your supply pipe has a resistance and the pressure at your property will reduce from the 6 Bar at the street main as more flow is taken by you.

You need to know the inlet pressure to the prv!

Tony

 

[Charnwood]

We know the pressure after the prv can be turned up to 6 bar, so that means the pressure at the inlet must be 6 bar. It can't be any less, I suppose it may be a little more as the prv only adjusts up to 6 bar.

It can be a lot more. PRVs are adjustable between 1 bar and 6 bar, but on most the inlet pressure most will take up to 20 bar.

Any pressure on the inlet side over 6 bar will be, if the PRV is set to max, 6 bar.

View media item 63251

 

[indus]

First off I don't really understand what Agile is on...

Put simply flow through a pipe is based on velocity x bore, [for the pedants yes I know there's more to it but lets accept the premise for the sake of simple explanation.]

The deciding factor in your case is the bore of the PRV, its ability to pass water at a given volume at 3bar down stream is finite, providing you have in excess of 3 bar plus resistance losses through the PRV up stream.

You say you have 6bar but you have not measured it, if I understand correctly. you do not know what the bore of the incoming mains supply is.
You mention a 22mm dia but fail to say what the pipe is. Is this after the PRV or before? depending on the material will depend the true bore of the incoming main. if its the incoming main then an approx. 22mm dia pipe could have a less than 1/2" bore. if its barrel then after 60 or so years it could be considerably smaller bore.

You should understand that 32mm MDPE main whilst it has a larger bore at only 26mm in bore size it is not that much different than say a 22mm copper pipe, but yes it larger.

you need to know the size of the PRV and its flow characteristics at 3bar output to know if it is suitable for your purpose. only the manufacturers can give you that information. The flow through a ½” PRV set at 3bar will be less than the flow through a 1” PRV set at the same output pressure, irrespective of the incoming mains provided it is in excess of the output by more than a small margin.

A further complication is that the PRV will control the output at the installed point of the PRV , the height of you property and the point at which water is delivered are remote so 3bar @ the PRV will not translate to 3bar three stores up.

So you see the question is easy, but the answer will depend on a lot more information than you have provided.

As a general principle the routing of the mains to as close a point of delivery before you drop / control the output pressure is probably the better solution, but it may also not be the best!

To be honest before you part with your hard earned you would be better off getting a qualified plumber who can see your situation first hand and interpret from knowledge and experience.

I hope that does not sound condescending as its not meant to be.
Good luck

Thanks for your help and no your post does not come across as being condescending

Can I give you some more information?

1) I have measured the pressure (after the prv) and it is 6 bar. The first pic shows the prv and the second shows the prv with the gauge attached.






2) The pipe from the street main to my boundary is the old 'lead pipe'

3) The existing lead mains pipe within my boundary was replaced about 6 years ago. It was replaced with MDPE, it was at least 22mm (but may have been 25mm??)
The first time I see the mains coming up from my suspended floor it is a 22mm copper pipe.


Thanks

 

[Weedrip]

Hi

here is a link to your valve type. its not 22mm connections but 3/4" unions, however the internals are probably not dissimilar judging from your pic.

http://www.caleffi.com/en_IT/Technical_brochures/01085/01085.pdf

do you know or can you judge the distance from the main boundary stopcock to the property? it would be useful to know did they replace the stopcock also when the new main was installed.

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