Boiler is slowly dripping on outside wall but works perfectly fine

unwashed potato!

unwashed potato!

unwashed potato!

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We have a maxi 600 or 800 boiler (I forget exact size) which we have had since 2019

Ita never missed a beat, works perfect, however there is a drip vent thing that goes to our exterior wall that comes out the boiler and it is constantly dripping. The bricks outside are saturated and never get dry.

We also now have water coming into out kitchen ceiling sometimes when it rains, and this is directly below where the leak goes down the exterior wall. I should add it never comes in the kitchen ceiling unless we have heavy rain so I can't be sure the 2 are related, though it seems odd that they would be the same place and not be related.

I have had quotes to get someone round, but it's £120/150 for an hour before they've even confirmed the issue and done anything.

But is this an issue? The vent is there for a reason right. The boiler works perfectly fine.

If the vent didn't aim back towards the house the water would drop onto the flat roof and not hit the brick and we'd be none the wiser
 
Do you have a water tank and if so is it a pressurised system? (unvented)

It sounds like it may be.

One simple check if you have a tank, you will have a tundish which looks like two egg cups facing each other in the middle of a pipe. Thats the drain pipe and its a pressure relief.
Assuming this is all correct, it sounds like you have lost the air bubble which provides expansion on the system
There are some other risks though, like the pressure relief itself not working correctly.

So the water heats up, and as that creates pressure it should simply compress an air bubble.

I had the same issue with my kitchen ceiling in that it would get wet. It was due to the tundish as it wont collect all the hot water if it comes out quickly.
Over time it slowly soaked through and then failed.

Assuming all the above, there will be instructions on the tank on how to reinstate the air bubble.
Its a list of doing certain things in order and the end result is a reinstated air bubble.
 
Do you get it serviced? Some of these have a siphon trap for the condensate which is supposed to help prevent the outlet freezing in cold weather.

I had the siphon block with bits of sediment on my Worcester Bosch so the condensate didn't drain.
In my case, the sediment likely entered via the balanced flu which points up, or could be from combustion impurities.
 
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unwashed potato! said:
We have a maxi 600 or 800 boiler (I forget exact size) which we have had since 2019

Ita never missed a beat, works perfect, however there is a drip vent thing that goes to our exterior wall that comes out the boiler and it is constantly dripping. The bricks outside are saturated and never get dry.

We also now have water coming into out kitchen ceiling sometimes when it rains, and this is directly below where the leak goes down the exterior wall. I should add it never comes in the kitchen ceiling unless we have heavy rain so I can't be sure the 2 are related, though it seems odd that they would be the same place and not be related.

I have had quotes to get someone round, but it's £120/150 for an hour before they've even confirmed the issue and done anything.

But is this an issue? The vent is there for a reason right. The boiler works perfectly fine.

If the vent didn't aim back towards the house the water would drop onto the flat roof and not hit the brick and we'd be none the wiser
Click to expand...

There's a few things that might be going on here. There will always be a pressure relief valve that's suppose to vent pressure if something goes wrong and there's too high pressure in the boiler. This is not supposed to drip, and you would end up with low pressure in your boiler. What you might be looking at is a condensate pipe, which is part of the normal operation of a condensing boiler. These are routed internally if they can be (to stop them freezing) or are outdoors and over drains. Old school installation would just stick something similar out the wall as old, non-condensing boilers would have just had a manual pressure relief/drain out there.

The rain leak may be an unrelated roof issue, or maybe a vent installation that hasn't been properly sealed.

I would get it checked out professionally. A service would not go amiss. Your condensate pipe should be routed properly, a pressure relief valve should not be dripping, and the vent should be correctly installed and not let water in. Gas boilers can have a pretty catastrophic failure state, or at best leave you without hot water and heating. Checking things out safely usually needs specialised knowledge and tools, and it's worth it for safety's sake. It's also illegal to open a boiler unless you know what you are doing.
 
Gammawolf said:
That's a pressure relief pipe. It shouldn't really be dripping constantly - for it to do so I'd assume you are filling up the loop a fair bit? If the pressure readings are ok and its still dripping then I'd say likely a faulty/stuck pressure relief valve.
Click to expand...

Never filling it

Mercenary Keyboard Warrior said:
Do you have a water tank and if so is it a pressurised system? (unvented)
Click to expand...
Yes
 
Is the pressure dropping?

Sounds similar to what was happening to mine, water running out of the pipe outside and soaking the brick, it was dropping and settling at 0.5 and when topped up would drop back again

It was a faulty PRV IIRC, a Glow Worm boiler about 7 years old, the part was fitted in half an hour, I think it was about £120 for the job and it's been fine since
 
Relentless81 said:
Is the pressure dropping?

Sounds similar to what was happening to mine, water running out of the pipe outside and soaking the brick, it was dropping and settling at 0.5 and when topped up would drop back again

It was a faulty PRV IIRC, a Glow Worm boiler about 7 years old, the part was fitted in half an hour, I think it was about £120 for the job and it's been fine since
Click to expand...

No that's the strange thing. Been like this a month now. Zero issues. I'm not touching it. Nothing has changed
 
Check your top up valve is completely closed and has not been knocked slightly open.
That water has to come from somewhere and if your not topping up and not losing pressure
you are getting water coming from elsewhere.
 
Easiest way to see if the water is coming out of the pipe or finding its way along the outside of it from some place else would be to attach a small plastic bag to the the end of the pipe, use an elastic band or something to hold the bag in place and seal it to the end.

If there's water in the bag after a while you know it's coming out the end of the pipe, if it's empty and a bit wet on the outside you know it's running along the outside of the pipe from some place else.
 
Murphy said:
Easiest way to see if the water is coming out of the pipe or finding its way along the outside of it from some place else would be to attach a small plastic bag to the the end of the pipe, use an elastic band or something to hold the bag in place and seal it to the end.

If there's water in the bag after a while you know it's coming out the end of the pipe, if it's empty and a bit wet on the outside you know it's running along the outside of the pipe from some place else.
Click to expand...
It's definitely coming from inside the pipe. I can see enough of the copper pipe to see it's coming from inside, and the pipe is so short coming directly from the boiler the internal side of the same wall.
 
If you have a pressurised system its almost certainly what I said
Lack of expansion bubble inside tank

Find the instructions for reinstating the air bubble (probably on a label on the tank itself), its a normal thing that happens and is a user not an installer fix, if that doesn't fix it then chances are the pressure valve itself is the issue
That also happens but is far less frequent.

What you can do to help diagnose is switch water heating on and see if it happens after a while on that cycle, that would confirm its an air bubble issue

Edit to add, people who haven't had a pressurised system will not get how they work. The water escaping is not the loop, its the tank water.
 
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Personally I would treat the kitchen leak as a separate thing and get that look at asap,
The vent thing, do you mean the flue or the condensate pipe?

Caviat, I have a combi boiler which may be very different.
 
unwashed potato! said:
i'll have a look thanks.

but how does the tank water get to this pipe?
Click to expand...

As I said before tundish in an overflow pipe. (tundish will look something like this https://www.amazon.co.uk/Universal-...&hvtargid=pla-2281435176898&gad_source=1&th=1)
By law unvented (pressurised) tanks must have a copper pipe that runs outside from the tank. Its probably halfway up or something.
Mine goes from the tank across the kitchen ceiling void, down the inside of the cavity and out the wall

When you say you have a kitchen ceiling leak, thats exactly how mine showed when I was venting excess pressure as the tundish is open and couldn't cope with the water coming out under pressure
So some would escape and as every heating cycle would overflow a bit more it slowly worked its way through
 
unwashed potato! said:
We have a maxi 600 or 800 boiler (I forget exact size) which we have had since 2019

Ita never missed a beat, works perfect, however there is a drip vent thing that goes to our exterior wall that comes out the boiler and it is constantly dripping. The bricks outside are saturated and never get dry.

We also now have water coming into out kitchen ceiling sometimes when it rains, and this is directly below where the leak goes down the exterior wall. I should add it never comes in the kitchen ceiling unless we have heavy rain so I can't be sure the 2 are related, though it seems odd that they would be the same place and not be related.

I have had quotes to get someone round, but it's £120/150 for an hour before they've even confirmed the issue and done anything.

But is this an issue? The vent is there for a reason right. The boiler works perfectly fine.

If the vent didn't aim back towards the house the water would drop onto the flat roof and not hit the brick and we'd be none the wiser
Click to expand...
It’s on purpose. When
Mercenary Keyboard Warrior said:
If you have a pressurised system its almost certainly what I said
Lack of expansion bubble inside tank

Find the instructions for reinstating the air bubble (probably on a label on the tank itself), its a normal thing that happens and is a user not an installer fix, if that doesn't fix it then chances are the pressure valve itself is the issue
That also happens but is far less frequent.

What you can do to help diagnose is switch water heating on and see if it happens after a while on that cycle, that would confirm its an air bubble issue

Edit to add, people who haven't had a pressurised system will not get how they work. The water escaping is not the loop, its the tank water.
Click to expand...
Not necessarily. Both boilers and unvented cylinders have pressure relief valves.

If it is one on the cylinder then you need to be G3 qualified to replace it. Just get a professional in.

It should be obvious from the location which it is. Just follow the pipe in through the wall.. does it go to the boiler? It’s the boiler PRV. Does it go to a tundish and then to the TPRV/PRV on the cylinder/cylinder supply? It’s one of those.
 
Will be the expansion vessel failed. Get that replaced and should fix the problem.

Obviously get a professional round to confirm and carry out the works
 
It could be failed O rings behind the head exchanger. Can be temporarily fixed by tightening them up.
 
Mercenary Keyboard Warrior said:
Do you have a water tank and if so is it a pressurised system? (unvented)

It sounds like it may be.

One simple check if you have a tank, you will have a tundish which looks like two egg cups facing each other in the middle of a pipe. Thats the drain pipe and its a pressure relief.
Assuming this is all correct, it sounds like you have lost the air bubble which provides expansion on the system
There are some other risks though, like the pressure relief itself not working correctly.

So the water heats up, and as that creates pressure it should simply compress an air bubble.

I had the same issue with my kitchen ceiling in that it would get wet. It was due to the tundish as it wont collect all the hot water if it comes out quickly.
Over time it slowly soaked through and then failed.

Assuming all the above, there will be instructions on the tank on how to reinstate the air bubble.
Its a list of doing certain things in order and the end result is a reinstated air bubble.
Click to expand...
Gone and had a look now and this appears to be exactly the issue. Constant water going through tundish.

It's definitely something that a home owner can sort? I had a look at a video and assuming the instructions are correct, it's a case of stop water from entering the hot water tank. Ensure heating of the hot water is turned off. Open downstairs tape. Open the valve on the top side of the tank that goes to the tundish. Keep it open until it stops gurgling.

Done?
 
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