Hot Water Pressure Help Please

25 Sep 2008
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South Glamorgan
United Kingdom
My hot water pressure has a slight problem (combi boiler)

You turn on the hot water (in the sink say) and the flow is fine and the combi kicks in, but then after a few seconds, the flow decreases rapidly, the water goes all cloudy until eventually the combi goes off.
You increase the flow and the flame kicks back in again and is fine but then the flow decreases again (and temperature of the water is really hot when the flow decreases!).
You need to turn the hot tap on quite a bit (well a few extra turns) before you get a good flow and temperature then it's fine.
Although the harder you turn the cold on at the same time, the more the hot flow decreases.

This happens in the downstairs sink (right next to the boiler) but I dont seem to get the problem when filling the upstairs bath or sink upstairs - one turn and it comes out fine?)

Now it's always been like this so hasnt bothered me - when you do the dishes you just have to give the hot a few turns as opposed to the cold just the one.
But I've had a single control thermostatic mixer shower fitted and due to the difference between hot and cold, the cold is overpowering the hot in the shower and its really cold.
Even if you turn the control right over to hot, it only gets very slightly warmer.

You can feel the pipes behind and the hot water is coming through (as the pipes are getting warm) but when you feel the cold water pipe, the water is rocketing through and overpowering the hot.

Someone has mentioned I may need to "top up" the boiler?

What I need is for the hot and cold to come out at the same rate with the same amount of turns on the tap so the shower pressure is equally balanced.

I'll be getting the make and model of the boiler at dinnertime so I can look for a manual but does this seem like an easy job to do?
If indeed "topping up" the boiler is what needs to be done?

Thanks in advance!
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