Some weeks ago I asked here if anyone knew what was going on with my hot
water supply essentially drying up after a few minutes when running a bath.

Well it wasnt such a big deal as mostly I shower, but today whilst
shaving after a shower the hot tap basically stopped altogether.

Cold tap worked fine, so it had to be something in the HE circuit

This prompted me to take up the matter again and lo! the internet is
FULL of stories about pressurised cylinders where the input pressure
regulator fails in some way.

I didn't even know these things HAD a pressure regulator!

It appears that the cold feed comes in via a preset 2.1 bar regulator
and filter assembly and thats what the tank should run at. There is an
air bubble in the top that is the 'pressure vessel' and an 8 bar
'overpressure' dump into the tundish. If something goes wrong with the
air bubble.

If flow is restricted the pressure will be there and as long as the air
bubble does its job, it will be 2.1 bar slowly falling until expansion
is complete then sweet fanny adams. I think that this probly means that
the pressure valve is doing its pressure thing, but the input filter is
so clogged with scale it can't handle replenishing water at the rate needed.

Which raises the question as to whether the water softener is in fact
working properly.

I did have root around inside the salt bit to see if that was OK, and
found a drowned mouse....what!!!!???? yes. A drowned mouse.!

This also would explain why I have been getting air in the hot water
taps. The bubble has expanded so MUCH that some of its air is getting
into the hot water outlet which is near the tank top...

Anyway although a qualified plumber is supposed to do this, I have
ordered a replacement regulator which, after switching off the leccy to
the immersion and CH system, turning off the inflow to the tank and
draining down the tank (open the lowest hot tap in the house and push
the tundish test thing to let air in: also will remake the 'bubble'),
should be unscrew and refit, corrosion permitting...

Wish me luck..




--
Karl Marx said religion is the opium of the people.
But Marxism is the crack cocaine.