Hello all,

I've just got my new Grant Combi 70 oil fired boiler up and running
(passed BCO inspection and has been commissioned).

A similar problem to mine was listed last week withou any replies so
maybe no one knws the answer but here goes.

I'm having problems with the domestic hot water side, heating is OK.
The DHW is coming out milky with dissolved air but is hot initialy
(after cold in pipes has been pushed through). The pressure then drops
dramatically to almost a trickle and the water is luke warm. Pressure
then picks up a bit when I open the taps further but not full mains
pressure. This happens with the boiler thermostat at all settings,
including full on. There is full mains pressure at the hot taps if I
use with the boiler switched off but only cold water as expected. So I
don't think there is any pipe restrictions causing this. I live in a
bungalow and have the same symptoms at all hot taps.

I have good water pressure and I think I have good flow rate but have
not had these measured. I could pressurise the boiler to over 2 bar
without a problem when filling and bleeding the radiators - it's back
down to 1 bar now before anyone picks up on that. As far as flow rate
is concerned, when I fitted lever operated taps in the kitchen I had to
install a restrictor to prevent having an indoor water feature if I
turned the tap past 1/4 turn and there is a good constant flow at the
bath cold tap. I have no other indication of flow rate other than maybe
timing how long to fill a large bucket.

After reading the manual I'm suspecting the diverter valve or diaphragm
but I'm new to combi's so not entirely sure. Am I right before I lay
into Grant for a fix?

Regards

Jimmy

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