DIY Doctor

How can I test if hot water tank has a leaking coil

Postby bobw » Sun Mar 18, 2007 10:24 am

Problem:- My hot water expansion tank keeps filling up to overflow I have replaced the ball float still fills up and have now turned off the in inlet supply. Still have the same problem. I have checked the stop valve and it does not leak. So I now think that the coil in the hot tank has a leak ( we have acid water ) . How can I test for this leak so that I do not have to go out and buy a new tank to find out it is not leaking.

Rank: Labourer
Progress to next rank:
Posts: 2
Joined: Sun Mar 18, 2007 10:10 am


Simply Build It

Postby tamz » Thu Mar 29, 2007 7:06 pm

It is not very likely that the coil will be leaking.
Your problem is probably caused by the water level in the expansion tank being set too high. When water heats it expands and the extra volume, on an open system, goes to the "expansion tank" rising the water level.
If the water level in the tank when cold is high enough, when it heats it will rise to overflow level. When it cools again the ballcock will top the system back up again. This cycle will keep repeating every time the system is run.
Fix this by adusting the lever arm of the ballcock or bend the arm down if it is brass. You should only have half a tank of water when the system is cold with enough room for the expanding water. This is assuming you have a standard sized system. If the system is larger capacity you may need a larger tank to allow for the greater volume of expansion.
You can check the coil by marking the water level in the tank when the system is cold. Leave system off for a few hours then recheck the level.
You could also drain the system and disconnect the flow and return on the cylinder. You will see any leak.
Rank: Apprentice
Progress to next rank:
Posts: 6
Joined: Thu Mar 29, 2007 6:41 pm

Postby Aarovic » Thu Apr 05, 2007 8:13 pm

You may want to check if you have a shower mixer that has tank fed hot water and mains fed cold water. Quite often if no non-return valve is fitted to the hot water side mains water can seep through to the hot water cylinder and fill the system up to overflow level. To check this leave the mains cold water turned off over-night and check cold feed cistern level in the morning.
Rank: Apprentice
Progress to next rank:
Posts: 16
Joined: Mon Apr 02, 2007 8:11 pm

Postby bobw » Thu Apr 26, 2007 8:56 pm

Hi thank you for your help it is the tank coil that is leaking. Now looking for a stainless steal tank to cope with our acid well water!
Rank: Labourer
Progress to next rank:
Posts: 2
Joined: Sun Mar 18, 2007 10:10 am

Postby Debbbie Dinning » Mon May 07, 2007 8:22 pm

I wonder if anyone can help. I have just been in to my airing cupboard and found that I have a leak on the top nut of my hot water cylinder. It seems to be a small leak. is there a gasket/washer I can replace rather than having to relace the whole tank. Fingers crossed. Any advice wellcome.

Many Thanks :shock:
Debbbie Dinning
Rank: Labourer
Progress to next rank:
Posts: 1
Joined: Mon May 07, 2007 8:06 pm

Postby thedoctor3 » Mon May 07, 2007 9:54 pm

Its probably a compression coupling and could be cured by tightening Debbie . Best idea is to undo coupling and refit using ptfe tape. Should get a plumber in for this as the water needs to be turned off.
Rank: Tradesman
Progress to next rank:
Posts: 33
Joined: Wed May 02, 2007 7:37 am

Display posts from previous
Sort by
Order by

  • DIY How to Project Guides
  • DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!

  • Related Topics