Water from overspill pipe during the night

[sk15kev]

I feel guilty about registering just to post and ask a question but hopefully someone can provide some help.

We have an immersion boiler which does hot water only. It is fed from the water tank which sits about 2 feet above it.

Our heating system is a seperate back boiler wood burner.

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The problem we are having is that every night (and it only seems to happen in the early morning 3 to 4 am-ish) water comes drips out of the over spill pipe and fills at least half a standard bucket.

My initial thoughts were that it was the element inside the boiler was either set too high or broken. I have turned it down and also subsequently turned it off during a couple of nights and it has seemed to have made no difference.

Before I go tearing things apart and breaking something else as I usually do, does anyone have any clues as to where to start?

thanks

 

[mrgas]

Ball valve dripping filling up to overflow level when not used at night

 

[sk15kev]

I suppose that is a possibility, but it doesn't seem to happen if not used for long periods during the day.

Will double check it though! thanks for replying so quickly.

 

[mrgas]

The overflow pipe is supposed to terminate outside the building.

 

[TicklyT]

The mains water pressure can creep up overnight as usage everywhere falls off.

If the float valve is poorly adjusted, or nearing the end of it's useful life, it may only start dripping as the mains water pressure rises.

Normally float valves are set to cut off when the water is a couple of inches below the overflow level.

If the float level is set a bit high, or the valve washer has worn a bit, the valve may not shut off until the tank is completely full.

When the immersion heater, presumably running on 'Economy 7' or a similar tariff, warms things up overnight, the water in the cylinder will expand back into the cold feed tank. if that is already full, the only place it can go is out the overflow.

 

[sk15kev]

Sorry haven't been able to get on for a few days.

Thanks for the detailed response. I will def give it a go.