Unvented Heater Leak

[Andyw123]

Hello,

I appreciate this might not be something I can fix myself, but I've called over 30 heating engineers this morning and they are either busy or on holiday until the new year. I even called emergency, 24/7 numbers but they aren't working until January either

Yesterday we noticed a leak coming through the bathroom ceiling. In the cupboard above we have 3 OSO unvented heaters. I checked for leaks and noticed water coming through the tundish on one of them. Unfortunately the water is also going over the floor which is creating the leak in the ceiling. I put a tray underneath last night but it fills up within a couple of hours. I tried turning the cold water feed into the tank off, thinking it would help but it actually effects the flow of hot water out of the taps.

The pressure looks to be very high, but not sure what to do. We go away on the 28th and my 80 year old parents are staying in the house. I really dont want them to be crawling into the cupboard and emptying the trays every couple of hours. Is it possible to tape the tundish to stop it leaking water over the sides?

If anyone in Cheshire or North Wales reads this and can help, please get in touch.

 

[Madrab]

Yes, your unvented is overpressurising when it's heating up, forcing open the pressure release valve and causing it to run the released water to the tundish and out to a drain. The system needs serviced

All you can do is get the tundish looked at and find out why it's leaking. It should run straight down through the tundish to the drain without leaking.

Sometimes there's dirt/dust in the pipe that is catching the water running into the tundish and pulls it to one side making it leak over the edges and simply running a finger up into the pipe where the water is coming from and rubbing/cleaning it can clean any dirt away making it flow into the tundish properly again, worth a try. You could put a bit of tape on one side I guess to deflect the water back in but it's not ideal.

 

[Rodders53]

When were those tanks last serviced?

I have a bigger OSO single tank in my 'airing cupboard.
Oso use an 'air bubble' in the top of the tanks to allow for HW expansion and contraction with heating. This air slowly gets absorbed into the HW. So the bubble needs regular replenishment (either as part of a service or following the instructions on the tank side/user and installer manuals).

If the bubble is gone it will vent to the tundish(es) as the water is incompressible cf the air...

NB OSO also allow a separate expansion vessel to be fitted an that allows a larger HW storage within the same tank. If there is one out of picture then the 'bubble'(s) won't exist.

 

[Andyw123]

Thank you both for the replies. I'll go an check to see if I can clean the inside of the pipe.

We only moved into the house a couple of months ago and all we know is the boiler was serviced in January. Not sure if that included the whole system though. I think there is an expansion vessel by the boiler but thats about 30m from the tanks.

Someone is going to try and get to us later today, so hopefully it can be fixed. I'm not sure I should be messing with it, even though I'm tempted.

 

[Madrab]

Always worth reading the MI on the cylinders, as suggested there will be an internal bubble (air gap) that is user serviceable and you can do that yourself.

https://osohotwater.co.uk/wp-content/uploads/2021/10/Manual-20-series-RI-production-dates-2000-2010.pdf

Anything else though and you need a qualified engineer to work on the unvented cylinders, it's a regulation I'm afraid. If they have separate expansion then they would be white vessels (tanks) within the same location as the HW cylinders. Hopefully though your issue is already sorted.

 

[Andyw123]

We managed to get someone out on the 23rd, but unfortunately the issue hasn't been fixed. The pressure relief valve is faulty and needs to be replaced. I'm tempted to wrap some tape around the tundish to stop water spraying over the floor. Is this likely to cause any problems?

 

[Madrab]

I'm tempted to wrap some tape around the tundish to stop water spraying over the floor. Is this likely to cause any problems?

I won't actually cause any problems but it's not ideal. The reason a tundish is open like that is 2 fold

1) if there is a problem then it is visible
2) if the downstream discharge pipe becomes blocked then there is always a path away from the cylinder for the relief water, even if it is over the floor.

All that being said, if the issue is actively being dealt with and as long as the tundish isn't made watertight then it may be ok as a temp solution but it's not recommended. I am surprised though that the person visiting the job couldn't sort the flow out so the relief water runs true and doesn't run down the edge of the tundish?? It's usually just a matter of cleaning the tundish/pipe and/or repositioning the inflow pipe.