Hot Water is Dead - I suspect the Pump

[TwinkleBel]

I am a newbie, so please forgive me if I am lacking supporting info.

For the last few months, I have been experiencing problems getting hot water out of my taps: kitchen, bath and basin.

The problem isn't that the water is cold... The problem is with the water pressure.
- There's either no water coming out...
- or there is a pathetic dribble...
- or hot water blasts out after several minutes lag (sometimes up to 20mins).

This happens regularly - both at high demand times and low demand times (e.g. 3am)

I live on the 6th (top) floor of a block of 12 flats.
Water tank on roof to supply all 12 flats.
New pumping system (£30K's worth) installed for the whole building on Ground Floor) 1 year ago to resolve prior problems with water pressure to flats.
8 months later, pressure from my hot water taps is intermittent in my flat but none of my neighbours have this problem in theirs.

Thames Water say pressure to building is average 2.2-2.4 bar.
Pressure valve gauge under kitchen sink is at over 1 bar (and has remained stable for last 2 years).
I have additional pumps (specifically for my flat) for the CH and HW.
If I open hot water tap, I can hear HW pump working while HW is running, however, it's not doing anything when there is no water coming out.
Also have an immersion cylinder (temp. set to 70C)
Potterton Prima 40F boiler 'seems' OK as CH working fine.

Perhaps the HW pump is on last legs...
Could it be something more sinister? I don't know where to begin...
Any ideas?

Thanks in advance!

 

[TwinkleBel]

Just to add, I have a sneaky suspicion that it's probably the water pump but I have no idea what type it is or what it is called.
Just in case this turns out to bee the source of the problem, here's a pic:

Please help!

 

[bengasman]

Sounds like you have a blockage, probably a load of limescale

 

[TwinkleBel]

Thanks!
Any recommendations on where I should start?
I assume you mean a blockage in the pipe work. Is there an easy way to flush it out?

 

[bengasman]

Alas, no easy way to get rid of it, any way of telling where it is.
Best way is to clean the whole lot with lots of elbow grease. Quickest way is to find places where the pipe or connections narrow, and check those first.
The bad news is: my GUESS from behind the keyboard is a limescale blockage, could be various other things.

 

[TwinkleBel]

I have copper pipes that are soldered. Would the elbow grease mean cutting a section open and rodding the pipes throughout the flat?
I take it there's no de-scaling solution I can easily add to all the pipes and then flush out..?

Could it be problematic if I were to treat it as an 'air-lock'?

 

[TwinkleBel]

Update:
Plumber has been around and it appears to be due to the floor switch in the HW pump that is sticking.
(Fingers crossed that a replacement will sort it)