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Hot water flow reduces significantly

Postby BigAlinMinch » Fri Apr 29, 2022 2:31 pm

Hello All, my name is Alan and I have a tricky problem with my plumbing.
I have a condensing boiler which is 6 years old and regularly serviced. It is connected to a indirect hot water tank, as well as the central heating.
During the last 2 weeks I have noticed that when the hot tap is turned on, the flow is normal (high) and gradually drops to a barely usable low rate.

This applies to two bathrooms upstairs and a toilet, utility and kitchen sinks downstairs.

I have checked the pressure after the regulator and the pressure relief valves, i.e. just where the water enters the hot water storage tank.
The pressure is about 40 psi, (3 bar reducer) and this does not drop when the hot taps are turned on. Not initially, nor when the flow drops.

The area that I live in has very hard water, and we do not have a water softener. I can not easily get access to a point on or after the boiler where I can measure the outgoing pressure. Of course once it leaves the airing cupboard, all the pipes are concealed under fitted carpets, floor panels or inside walls.

Is it likely that the storage tank would have collected enough limescale in 6 years to obstruct the flow rate significantly? Is there any other way that an obstruction could have been created in the system?

Is it significant that the flow rate is a normal high flow initially, then drops off progressively after a few seconds? Does this suggest that some material is being drawn into a restriction in the tank outlet or pipe, by the flow.

Any helpful guidance will be gratefully received.

Alan
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Postby stoneyboy » Sun May 01, 2022 10:07 pm

Hi bigalinminch,
From your description you have a mains fed hot water cylinder. The pressure from your boiler is irrelevant.
It is unlikely that the tank is full of limescale but it may be that the pipe feeding out of the cylinder is furred up. Turn off the mains feed to the cylinder and remove the first section of pipe out of the tank to determine whether this is the issue,
Regards S
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Postby BigAlinMinch » Tue May 03, 2022 1:26 pm

Thanks for the input. What puzzles me is the fact that the initial flow rate is unrestricted. An obstruction in the outlet, would give a fixed low flow, I would have thought. It is worth a look anyway, so Thanks for the suggestion.

Best Regards
Al.
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Postby stoneyboy » Tue May 03, 2022 9:40 pm

Hi bigalminch,
Suppose it is a porous limescale plug, mains pressure will get past it giving you full pressure at the taps initially. Once the mains pressure is relieved by you opening a tap you will get a reducing flow due to the water remaining in the pipe work.
Regards S
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