Vaillant 242 Combi fitted approx 3 years ago. Gradual (?) loss of hot water
flow rate (down to 5L min). Lowish pressure incoming mains now sorted with
new plastic pipe to mains. Gas pressure checked OK. Turbulence noise (?)
apparent in region of hot water heat exchanger. Low pressure out of hot
water even with boiler turned off.
Any help appreciated!
There is some sort of blockage. Frequently, this is due to scaling up of the
heat exchanger. Do you have hard water? Do you have an ion-exchange
softener, or a phosphate doser? (Ignore magnetic or electronic water
"conditioners", they only work if you believe in the tooth fairy).
Other possibilities for blockages are inlet filters and partially closed
isolation valves. The latter isn't particularly likely as you say the
problem was gradual and progressive.
Agreed there is something restricting the flow. The water is very soft -
nothing visible in the kettle after over five years use!
I think that it's time to take off the DHW heat exchanger and eliminate any
blockage due to dirt (?). The isolation valve has been checked and is as
clean as a whistle.
Thanks for all your suggestions
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