Water Pressure drop

Tue 17 Mar 2009, 16:36

If the pressure in the pipe is high and there is a good flow rate then air will be sucked into the pipe through any small holes in the pipe creating bubbles of air in the water (Venturi effect). This is the same principal (though kind of inside out version) as when you're travelling in a car and slightly open the window causing the air pressure to drop in the car, sucking air out rather than blowing air in.
I think this is a more likely cause of the bubbles rather than gas being dissolved into the water because the bubbles appear to be already in the water as it enters the glass rather than nucleating once entering the glass and depressurising from the water pipe.

Sorry I've no suggestions on curing the problem though :-)

Fri 13 Mar 2009, 20:27

I agree with you Janet, I think the pressure is extremely high. A few months back I had to have a pressure regulator fitted to my incoming mains supply in order to stop pressure backing up through the system and causing a constant drip from the unvented boiler over flow. It took the plumber a few trips to find out where the problem was. The regulator has done the trick, but we still get a bit of pipe hammer.

Fri 13 Mar 2009, 19:41

"have to run the cold water now for 15 to 20 seconds as it's very cloudy in the glass." This is more likely to indicate a pressure INCREASE than a drop of pressure in your case - the cloudiness, if it isn't obviously particles, is gas coming out of solution in the water as the pressure is released, in the form of little bubbles. I've noticed this too on a number of days. The atmospheric pressure is about 14lbs per square inch, water pressure in the pipes can be easily 5,6+ times that and hence gases will be forced into solution.

If not particulate nothing to worry about, though aerated water can taste a bit odd (same principle as carbonating fizzy drinks basically).

I'd say we've had a bit of a pressure *increase* up here at the top of Enstone Rd area the last few weeks, as there has been a marked incidence of water hammer in the mains system when turning off taps suddenly, and outgassing too. I'd guess, if so, this is probably due to the messing about with the piping system as it sounds like renewal of mains is taking place around the area, and getting unbalanced pressures in the pipe network as they try to make sure water supply gets to the top of various hills via indirect and/or longer routing lengths or constricted pipe bores in the indirect routes, all of which would or could result in a desire to increase pump station pressures where the water enters the system??

Fri 13 Mar 2009, 14:28

Thanks to all - the problem now seems to have righted itself naturally.

Wed 11 Mar 2009, 14:04

thats only just started and its going to be going on for 8 weeks as they are closing the high street in finstock soon.

Wed 11 Mar 2009, 13:36

there is work going on in Finstock at the moment. Would that be having any effect on you in Charlbury?.

Tue 10 Mar 2009, 19:41

Caroline, I posted a notice about a drop in water pressure last September, but did not get much of a response. We do still experience this from time to time, especially first thing in the morning about 6-8am. We live in quite an elevated postion in Charlbury, and I do not know if this is relevant. At times, the pressure is too low to operate appliances effectively.

Tue 10 Mar 2009, 09:10

That sounds like pipe work being carried out somewhere between you & the pumping station...

Sat 7 Mar 2009, 11:57

I have not noticed the pressure drop, but I have noticed i have to run the cold water now for 15 to 20 seconds as it's very cloudy in the glass.

anyone have any ides?

Sat 7 Mar 2009, 10:58

Has anyone else experienced a drop in water pressure? This is affecting both my combi boiler and my washing machine.