Three loft tanks - which one causes dripping overflow?

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Hi folks, I'm new on here, just joined today, this is my first post.

First let me apologise because I've had a look around before writing, and I can see that my query is very similar to others already on here. However, I'm hoping that you will think it is sufficiently different to justify creating a new post rather than adding to an existing one, when I explain.

Three months ago we bought a second property, (investments going nowhere with the tiny interest rates!), it's a 1960's bungalow in Yorkshire. It has been extremely well looked after, and is in excellent all round condition. However, there is this dripping outside overflow pipe. Not pouring out, only a single drip at a time, but fairly constant nevertheless.

Up in the loft there are three water tanks, (most of the other posts only refer to having two). One large one, pretty obviously the cold water tank, mounted on a wooden platform or frame. Directly below that on the same platform, is a very small one, which I can only guess could be to supply the electric shower in the bathroom, but may not be. A couple of feet to the left of these two is a third tank, around two-thirds the size of the large one, on its own platform. I have no idea of the function of that one, but conceivably it could be to top up the main hot water cylinder, which is located in a cupboard in the kitchen, next to the oil-fired central heating boiler.

The water level in the largest tank is maybe 10cm below its overflow outlet with the ball valve floating nicely and not turning the top-up input on. So that's surely not the source of the drip from the pipe outside.

The water level in the medium-sized tank is only about 2cm below its overflow outlet, but again the ball valve doesn't seem to be a problem, it has not been adding water whenever I've looked at it, though presumably it does when necessary.

That leaves the small tank. The water level in that, this morning, was slightly above the bottom edge of its overflow pipe so I thought I'd found the cause of the dripping. First I bent the arm of the ball valve down a little more than it had been. Next I used a jug and bucket to remove water, (about twelve litres), until the ball valve dropped enough and duly opened the water input valve. I then watched it fill up. The ball shut off the supply when the water level was around 8cm below its overflow outlet - presumably thanks to my bending of the arm.

Job done - I thought! but a couple of hours or so later, the outside overflow, which I thought had ceased when I partially emptied the small tank is now again consistently dripping, one drop at a time approximately every 30 seconds - yes I've been and timed it (sad life!!).

Anticipating that some of you may suggest that I establish exactly where these tanks are feeding to and from, there is a problem with doing that. The loft is a large one. When we bought the house it was floored with a good amount of insulation, and we took advantage of our age to qualify for adding a great deal more fibre-glass on top of the existing, all done for us by a professional firm, for only £99. So the prospect of trying to shift significant areas of fibre-glass sheets and peer beneath it is not greatly attractive!

Thoughts appreciated.
 
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Have you checked if it the water in the small cistern is at the overflow level again?
 
That leaves the small tank. The water level in that, this morning, was slightly above the bottom edge of its overflow pipe so I thought I'd found the cause of the dripping. First I bent the arm of the ball valve down a little more than it had been. Next I used a jug and bucket to remove water, (about twelve litres), until the ball valve dropped enough and duly opened the water input valve. I then watched it fill up. The ball shut off the supply when the water level was around 8cm below its overflow outlet - presumably thanks to my bending of the arm.
If you have a radiator central heating system, that is probably the Feed and Expansion tank. It supplies water when the system needs to be filled and absorbs the increase in volume when the water is heated. This increase in volume causes the level to rise. If the level, when the water is cold, is too high, the water level when warm can rise to the overflow.

Try bending the arm some more. The water level at which the valve opens does not need to be more than a couple of inches above the bottom outlet.
 
You need about 100 mm with the rads cold and it will rise to about 200 mm with rads hot.

Check those levels as there can be another fault involved.

Tony
 
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Denso13, D_Hailsham and Agile,
thank you all three for swift replies, I greatly appreciate it. As I said in my OP, this problem is in our second property in Yorkshire, 57 miles from our first home in south Nottinghamshire, where we have now returned to. Our next trip up to the bungalow is scheduled for 20th December, and we shall stay there until the 30th. I cannot therefore try any of your kind suggestions until then, but I certainly shall do, in the hope of sorting it before Christmas Day!

Denso13,
We left the bungalow at 3pm today, and it didn't occur to me to see if the small tank's water level had changed having dealt with it during the morning. I assumed that because I watched it fill up until it had stopped filling, stopped is how it would remain! On reflection, a very silly assumption. Can you tell I'm not a qualified plumber? !!! When I do get back up there, what might I expect to see, please?

D_Hailsham,
Yes the heating is indeed a normal water-filled radiator system. Thank you for your explanation about the likely function of the small tank.

I will try bending the arm some more, happily, but may I ask what that will achieve, given that the first bending I did today resulted in the ball valve shutting the water supply off when the level was around 8cm below the overflow outlet? I'd have thought that bending the arm further would simply cause the ball to shut off the supply at a level greater than today's 8cm below the outlet. As it's already 8cm below, how could it be causing the dripping from the outside pipe?

Agile,
All my measurements, (2cm, 8cm and 10cm), have been to indicate the distance DOWNWARDS from the bottom of the outlet overflow to the water level. When you say:
"You need about 100 mm with the rads cold and it will rise to about 200 mm with rads hot."
am I correct in thinking that you are measuring UPWARDS from the bottom of the tank to the water level, please?

Also, at this stage of your help, is it too soon to ask what other fault might be involved?
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D_Hailsham,
Yes the heating is indeed a normal water-filled radiator system. Thank you for your explanation about the likely function of the small tank.

I will try bending the arm some more, happily, but may I ask what that will achieve, given that the first bending I did today resulted in the ball valve shutting the water supply off when the level was around 8cm below the overflow outlet? I'd have thought that bending the arm further would simply cause the ball to shut off the supply at a level greater than today's 8cm below the outlet. As it's already 8cm below, how could it be causing the dripping from the outside pipe?
 
When I do get back up there, what might I expect to see, please?
I only asked the question to double check it was indeed the small one overflowing again. If it is try what has been suggested, bend the arm down so it only fills above the cold feed pipe (outlet) when cold. This should leave more room for expansion but if it continues to overflow there could be other, more problematic things going on.
 
Put different food colouring in the tanks and see what colour the water comes out the overflow (a plain rag tied round the overflow pipe will catch the colour so you don't have to watch it continuously)
 
I will try bending the arm some more, happily, but may I ask what that will achieve, given that the first bending I did today resulted in the ball valve shutting the water supply off when the level was around 8cm below the overflow outlet? I'd have thought that bending the arm further would simply cause the ball to shut off the supply at a level greater than today's 8cm below the outlet. As it's already 8cm below, how could it be causing the dripping from the outside pipe?

Oh dear!

You have ignored my advice!

The water level when cold should be just 100 mm depth!

That will rise to about 200mm when CH is hot.

That will give about another 100 mm to the overflow pipe as a safety margin.

You must set it like that if you want it to be correct!

Tony
 
Put different food colouring in the tanks and see what colour the water comes out the overflow (a plain rag tied round the overflow pipe will catch the colour so you don't have to watch it continuously)
That will do wonders when rinsing your delicates. :eek:
 
Wow Agile - an even faster response - great, thanks very much.
I wasn't ignoring your advice, (honest!). In my plumbing ignorance, (cheerfully admitted!), I just didn't fully understand what it might achieve. Ok, when we go up there on the 20th I'll make sure I set it exactly as you say. Thanks again for that.

Thanks too to you Denso13 - Ok, I see why you asked. I'll go with your advice as well.

Food colouring? Sounds a good idea, thank you OwainDIYer. I'll take care not to cause myself, (or my wife!), problems with 'delicates' as 45yearsagasman comments!
 

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