Hot water flow drops off quickly

[BigAlinMinch]

Hi, my name is Alan and I have a puzzle with my hot water supply.

I have a condensing boiler which is 6 years old and has been regularly serviced. It is a non-vented system, connected to an indirect hot water tank, as well as the central heating system. During the last 2 or3 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. Of course the pipes are all under the floor or in the walls, so not easily accessible.

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

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.

Is it likely that the storage tank would have collected enough limescale in 6 years to obstruct the flow rate significantly??

Any helpful guidance will be gratefully received.

Alan

 

[ShaunCorbs]

Sounds like your unvented cylinder needs servicing

 

[BigAlinMinch]

Sounds like your unvented cylinder needs servicing

Thanks for your input. You are probably right. It seems so, only 3 months after the last one, which cost £350 and involved replacement of the expansion vessel, and the pressure reduction valve/pressure relief valve inlet block.
Just to compound the puzzle the service instructions do not detail a remedy for this problem.

 

[ShaunCorbs]

If it’s only just been done I would ask them to come back (chargeable to check the strainers and test the system)