Hot water flow issue

[ShaunD]

I have a problem with my hot water and would appreciate some help. (apologies for using idiot language I am not in any way an expert, I just want to make sure I am not being taken to the cleaners by my plumber)

I have a hot water system with a header tank in the loft and an immersion heater / cistern setup. It has all worked fine for 7 years but a couple of months ago we started getting very poor flow with the hot water from all of the taps (upstairs and downstairs). This is intermittent, we occasionally get a heavenly couple of hours when we get very good hot water flow, but the majority of the time the hot water comes out as a trickle. Where we were once able to run several taps at the same time, only one now works. (barely)

We have had a plumber around, his first action was to flush the system with a de-scaler. This apparently flushed out quite a lot of junk but failed to make any impact on the hot water flow issue. He has now implied that the problem is being caused by a small diameter pipe from the header tank causing air locks in the system. He is suggesting putting in wider diameter pipes to fix the problem. This sounds a bit drastic considering the pipes have always been this diameter and have worked fne for much of the time. Why suddenly a problem ?.

Does anyone have any suggestions what might be causing our issues ? and whether what the plumber suggests is sensible ?

On other thing, we occasionally get a low humming from the pipes immediately around the cistern when we run a hot tap, not sure whether this is related.

Any help would be very much appreciated.

The house (and heating) is 12 years old, we have not had any work done on the plumbing (other than a yearly heating service) which could have triggered the problem

Many thanks Shaun

[Sylvain VAN DER WALDE]

I know almost nothing about central heating, however, something comes to mind: analogy of a car's blocked petrol tank cap breather. Are there any tank (?) breather holes or valves that might be blocked or faulty? Just a thought.

Sylvain.

[The Natural Philosopher]

Dead bird in the header tank, washing over the exit pipe.

Airlocks are not it..they will clear or become complete flow stoppers one or the other.

[Dave Plowman (News)]

That's an unusual course of action. My system - in London, a hard water area, is around 30 years old and never needed descaling.

Don't like 'apparently'. It would have been nice if you'd observed the results.

It would be an unusual system that didn't use 22 mm for the flow from the header tank to storage cylinder and from there to the bath tap and possibly shower. Other taps would normally be 15mm. Can you check on this?

I wonder if anything has been altered or damaged? Or a blockage - perhaps a failed cut off valve somewhere? Or foreign bodies in the header tank? Is it covered, and have you looked?

Your plumber doesn't instil much confidence. ;-)

First thing to do is to make sure there's no air in the system. The easiest way is to push mains pressure cold water back up the pipework from the kitchen tap. If you have a hot and cold outlet for a washing machine, couple a hose between these and turn both on for a couple of minutes only.

If not but separate sink taps couple a hose between those. If a mixer, firmly tape a reasonably tight fitting container over the nozzle - something like a plastic milk bottle should work. The idea is to force water the 'wrong' way up the hot circuit. Best to have an assistant check the header tank to make sure it doesn't overflow. While the high pressure cold is applied you could also check the flow from all hot taps is now producing plenty of (cold) water, via the high pressure input.

Is it possible other work may have damaged the pipework somewhere?

The first thing though is to make sure it's not an airlock by using the above method. If this clears it and it then works ok you have an answer. My guess is it will. Funny stuff air in low pressure systems - it can move around and never clear on its own.

[ShaunD]

Thanks for the comprehensive reply Dave.

I am pretty sure that there isn't any damage to the system and I have checked the header tank, there are no obstructions.

The plumber did the cold water up the hot tap trick when he flushed the pipes. We have excellent cold water pressure so I'm sure if this was going to work it would have.

One of the comments that has been made by another poster refers to the car radiator scenario...i.e a blocked air intake causing a vaccum. Could this be possible ? where would I look for such an intake ?, as I said I'm not terribly familiar with what all the pipes do !

In the mean time I am going to check out the pipe diameters and see if they are non-standard.

Again, many thanks Shaun

Dave Plowman (News) wrote: