Low mains pressure but only affecting cold water kitchen tap. Great pressure to outside tap.

[L Vincent]

Our house has a grundfos home booster pump due to narrow victorian pipes in our area.
We have been getting recurrent air locks over the past few weeks. After a grundfos engineer review, there is no inherent problem with the pump but the pressure of the mains water pipe refilling the water storage tank is low and the tank is taking far too long to fill. The airlocks are caused by the tank emptying fully (often after only 1 shower) and pulling in air. Previous mains filling of the storage tank was normal and 4 or 5 showers in a row did not cause any problem. We have a shared supply with our neighbours' houses but theirs are unaffected.

The pressure in the cold water kitchen tap is also low, (much less than the hot tap). Strangely the outside garden tap pressure is completely unaffected. It's unclear what's causing the issue whether there is some constriction/blockage selectively affecting some pipes or some other problem.

We would appreciate contact from an experienced plumber who can solve the problem for us. We have unfortunately had a plumber out previously who was of little use and suggested we have a powerflush (!). It would be helpful to have an indication of what you would be checking for as a possible cause for the problem - we would be reluctant to use the services of someone who can't solve the problem.

 

[Ric2013]

Water pressure - Ofwat

I note that the minimum required is 0.7Bar, but if you have this going through a thin straw, your flow will still be rubbish and, your storage tank will not fill. So it may not be the pressure so much as the flow (all to do with the difference between static and operating pressures).

It may be worth arguing the case with your water company if the defect is in pipework for which they are responsible (I do know a plumber who successfully aregued this with Welsh Water and got the company to remedy a fault which all her neighbours had been fobbed off about for 30 years), or replacing as much of your pipe as your are responsible for. Narrow pipes are one thing, but if it's actually a case of corrosion debris blocking the flow (which is what it sounds like) or a valve in your supply line partially closed, then buggering about with pumps is engineering what should be a simple but laborious job of fitting a new water main.

Unfortunately your post as written

It would be helpful to have an indication of what you would be checking for as a possible cause for the problem - we would be reluctant to use the services of someone who can't solve the problem.

and lack of information as to where you are doesn't help and will put a lot of people off. If you wanted an experienced plumber to come and look, it will take time to work out exactly what is going on and any speculation at this time and distance is not worth an experienced plumber's while when s/he could get the same information on site in minutes.

If the plumber couldn't solve the problem, or at least identify the cause of the problem, I don't think s/he would expect payment, but expect to pay a reasonable amount for the plumber's experience.

In fairness, your plumber's suggestion of a powerflush makes no sense (unless s/he was intending to somehow powerflush the mains?) but faultfinding is always going to be a painful task potentially requiring a lot of thought.

If I were you though, I'd be draining that storage tank and allowing it to refill, then telling us how many litres per minute that equals from your mains, then coming back here to ask if that would be considered a reasonable flow to expect from your mains supply.

And, for what it's worth, if your tank is 180 litres, I really don't see how you are draining that in a single shower. I don't use that much water in a day.

 

[ShaunCorbs]

He's in Berkshire