Mains water to house drop in pressure

[Ab12]

Thames water were out doing some work on my neighbours water meter today. So I asked them to do a pressure test for me as I've recently noticed a drop in pressure

My mains pressure was showing at nearly 4 bar, at the meter.

But when I test immediately after the mains stopcock inside my house (teed immediately to garden tap where I tested), the pressure is just above 2 bar..

Is it really possible to have a drop of circa 2bar pressure on a max 25m run of 25mm mdpe pipe?

Can a stopcock cause a pressure drop?

 

[JohnD]

Might be a leak. How old is the house?

Might be constriction of flow, if you were running water at the time you measured pressure.

Static pressure in house and in main should be the same if no taps are running, even if flow is constricted. It will drop when you turn taps on.

It varies during the day and is usually highest in the small hours.

 

[Ab12]

Might be a leak. How old is the house?

Might be constriction of flow, if you were running water at the time you measured pressure.

Static pressure in house and in main should be the same if no taps are running, even if flow is constricted. It will drop when you turn taps on.

It varies during the day and is usually highest in the small hours.

House is old 1930, MDPE pipe is new.

Tested for leaks (atleast from street to house stopcock) by turning off house stopcock and checking the meter after a couple of hours with no change seen.

No taps were running, what amount should it drop if the sink tap were on for instance?

Thanks

 

[Johntheo5]

Before doing garden tap test check static pressure and check again immediately after test.

Allow say another 3M for bends etc, using 28M of 25mm (20.4mm ID) MDPE shows the following pressure drop.
0.11bar at 15LPM
0.19bar at 20LPM
1.10bar at 50LPM

To get flowrate, run the water into a bucket/container for exactly 30 secs and measure it with a 1 pint or 1 litre milk bottle or whatever, if using a 1 pint measure, X by 1.14 to get the flowrate in LPM, if using a 1 litre measure, X by 2.0 to get the flowrate in LPM.

 

[Murdochcat]

Suppliers do reduce the pressure when it’s hot

 

[Ab12]

Before doing garden tap test check static pressure and check again immediately after test.

Allow say another 3M for bends etc, using 28M of 25mm (20.4mm ID) MDPE shows the following pressure drop.
0.11bar at 15LPM
0.19bar at 20LPM
1.10bar at 50LPM

To get flowrate, run the water into a bucket/container for exactly 30 secs and measure it with a 1 pint or 1 litre milk bottle or whatever, if using a 1 pint measure, X by 1.14 to get the flowrate in LPM, if using a 1 litre measure, X by 2.0 to get the flowrate in LPM.

What do you mean check static pressure and check again after test?

I have a pressure gauge which I attached to the tap and then I turn on the tap with no other taps on that gives me static pressure right?

What test are you recommending I do after that?

Thanks

 

[polesapart]

I have a pressure gauge which I attached to the tap and then I turn on the tap with no other taps on that gives me static pressure right?

YES
If you then turn on another cold tap fully e.g. a garden tap your gauge will then read the dynamic pressure.

 

[Harry Bloomfield]

Is it really possible to have a drop of circa 2bar pressure on a max 25m run of 25mm mdpe pipe?

Can a stopcock cause a pressure drop?

You seem to be confused by static, and dynamic pressure....

Static pressure, is the pressure, as measured when you have no water being drawn in your premises. It might vary, depending on when others draw water near you, on the same main.

Dynamic pressure, is the pressure measured when you actually draw water from another tap. The more bends, restrictions, and the longer your pipe, the more the dynamic pressure can drop. The more taps you turn on, the more the dynamic pressure can drop. As said, any restriction can reduce the dynamic pressure, but it will not affect the static pressure at all. So, if your stop tap is partially turned off, it can reduce the dynamic pressure and thus the flow.

 

[Johntheo5]

What do you mean check static pressure and check again after test?

I have a pressure gauge which I attached to the tap and then I turn on the tap with no other taps on that gives me static pressure right?

What test are you recommending I do after that?

Thanks

Like this.

 

[Dereekoo]

Thames water were out doing some work on my neighbours water meter today. So I asked them to do a pressure test for me as I've recently noticed a drop in pressure

My mains pressure was showing at nearly 4 bar, at the meter.

But when I test immediately after the mains stopcock inside my house (teed immediately to garden tap where I tested), the pressure is just above 2 bar..

Is it really possible to have a drop of circa 2bar pressure on a max 25m run of 25mm mdpe pipe?

Can a stopcock cause a pressure drop?

Did Thames use your pressure gauge or theirs, if different ones used one may be calibrated wrong

 

[Ab12]

Did Thames use your pressure gauge or theirs, if different ones used one may be calibrated wrong

They used theirs on the street mains, I used one I bought (artic hayes) on my stopcock

 

[Johntheo5]

They used theirs on the street mains, I used one I bought (artic hayes) on my stopcock

Can you take the pressure "now" with the test tap shut, then open it fully, note the pressure and then measure the flowrate as suggested.

 

[Ab12]

Can you take the pressure "now" with the test tap shut, then open it fully, note the pressure and then measure the flowrate as suggested.

I think measuring the pressure at the meter might be beyond my ability.

I just took static pressure at my garden tap. Showed 3 bar.

Turned on kitchen tap fully, which tees off this garden tap (extension) this didn't effect the pressure reading

Left on kitchen tap and turned on another bathroom tap downstairs fully, no effect on pressure

Left those both on and turned on the top floor bathroom tap fully, no effect on pressure.

So I can assume then I have good pressure I think.

Next I will check flow at these locations.

As an aside then, is there any way to boost a rainfall shower pressure/flow so that it hits harder, with a pump?

Thanks!

 

[Harry Bloomfield]

I just took static pressure at my garden tap. Showed 3 bar.

Turned on kitchen tap fully, which tees off this garden tap (extension) this didn't effect the pressure reading

Left on kitchen tap and turned on another bathroom tap downstairs fully, no effect on pressure

Left those both on and turned on the top floor bathroom tap fully, no effect on pressure.

That doesn't seem logical, unless you have a very large supply pipe, or the needle of your pressure gauge is stuck. Always with flow, there has to be some drop in pressure, due to resistance to flow, in the pipework. .

 

[Ab12]

That doesn't seem logical, unless you have a very large supply pipe, or the needle of your pressure gauge is stuck. Always with flow, there has to be some drop in pressure, due to resistance to flow, in the pipework. .

Needle moved when turning on the garden tap but didn't move when any other taps went on. I have a 25mm mdpe supply pipe