Hot water system noisy - wakes me up !!!

Is there a way to bleed the hot water system. Where would the bleed valves be if so. I know I have to bleed the central heating system regulary.
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two common things that can happen:

1) F&E short of water
(which you say it isn't, presumably you have pressed the ball down and water squirts in, like in a WC cistern? there should be no noticeable sign of water movement in the F&E at any other time)

2) blockage in F&E feed pipe which prevents water going down to refill the system (this is very very very common)
Is the bottom of the F&E thick with rusty mud?

If you bleed the highest radiator in the house, does water squirt out vigorously, with no drop in pressure as you vent it? What colour is the water?
(this is easier and quicker than drawing off a bucket of water from the drain cock and verifying that an equal amount of water is drawn down from the F&E)

I am just a householder but have experienced both these probs
the small tank is the feed and expansion which keeps the boiler and radiatiors full.

if there is no corrosion inhibitor, or if it pumps over or leaks, the radiators corrode and you get brown rust or black sediment. this causes blockages.

If you bleed the highest radiator in the house, does water squirt out vigorously, with no drop in pressure as you vent it? What colour is the water?

there ought to be a drain cock at the lowest point on the system, possibly close to a radiator near an external door or in the garage. some installations do not have one :rolleyes:

I've bled all the radiators in the house, (upstairs and down), and all appear to be fine. The pressure seems to differ in each radiator but the water appears to be clean. As mentioned though, the water in the small F&E in the loft is really quite dirty.

It definately sounds like air in the system - but other than switch on the central heating to circulate it, I can't think of another way of getting it out.
The first action is to check that there is sufficient water in the F&E cistern.

If you don't know what that means, please ask.
Please note that this involved merely observing, i.e. looking, and not any action, like pushing.

So, is there sufficient water in the F&E cistern?
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Yes, both main and smaller tanks are/were full before me pushing.
OK then.

Since the problem is reasonably recent, then the possible causes are:

1. Some recent plumbing work was carried out incorrectly;
2. A blockage in the cold feed causing air to be drawn down the vent pipe;
3. The system is corroding and is generating Hydrogen.

You haven't mentioned any recent work, so it seems unlikely that it's that.
The next step is therefore to see whether or not there's a blockage.

If you want to preserve the majority of any chemical inhibitor that might already be in the system, then you could shut all the radiator valves before doing this.

The method is as follows:

1. Shut off the supply of cold water to the F&E cistern.
2. Note the level of water in the F&E.
3. Locate a drain off cock on the central heating system.
4. Attach a hose to the DOC and take the end outside.
5. Open the DOC and allow at least 4 gallons to drain out, then shut the DOC.
6. Return to the loft and observe the level of the water in the F&E.

Most, if not all, of the water should have drained out.
If not, then the cold feed is blocked.

Please ask if you don't know how to do each step. Help (information) is readily available.
Am I observing the water level in the large F&E tank or the small one. If I drain water from the central heating system, I assume the smaller tank will drain. Am I right.

Will it drain the dirty water in to the system. Should I clean this out first.
The small one is the F&E for the boiler and rads. It is probably in the region of 500mm x 300mm x 300mm. It only needs a couple of inches of water in it above the outflow at the bottom (this gives maximum room for expansion when the system heats up).

the big tank feeds your bath taps and is not relevant today.

Rusty brown mud tends to accumulate in the F&E, so rather than let this flow down into the rads, it is a good idea to bale it out first. tie up the ball float while you do this. You will probably need a sponge to mop up the last of it.

It tends to stick the the sides but you can rub this off with your wet sponge.

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