Advice on leaking coil?

JoJen

I've been told hot water cylinder needs replacing due to leaking coil. I wanted to check out what others in the know think to make sure that's right. The cylinder was only replaced a couple of years ago.

- Problem started about two months ago, when the weather got colder.
- When the heating is on, no problems. When its off, there is water from the plastic overflow coming from the expansion tank (which is same level as cold water tank in attic).
- When I was first checking out problem I found that an insulation cover on top of the expansion tank had fallen in and gotten water logged - thought this might have bent the ballcock down, lowering level, but plumber only said no, don't be messing with it.

I don't understand why there's only overflow when the heating is off - if it was a leaking coil wouldn't it be happening when the heating was on? Anybody enlighten me?

If it needs to be replaced, fair enough, but could it be something else? Or is there anything else that could show it definitely is/not a leaking coil in hot water cylinder?

Thanks for replies.

southcoastrgi

The smaller tank is called a feed & expansion tank for a reason, the water in it should be around an inch above the outlet at the bottom, when the heating is on the level will rise slightly which is why it needs room, if the level is high remove the water so it's as I've already said & adjust or replace the ballvalve so it doesn't fill up anymore than that & see how that goes

DavidFx

If the water level in the cold water tank is higher than the water level in the expansion tank and there is a hole in the heating coil in your hot water cylinder then water will flow from the cold tank to the expansion tank.
If the water level in the cold tank is above the overflow in the expansion tank then water will flow from the overflow.
When the heating is on, the pressure in the heating system is higher due to the pumping action and this will reduce, stop or reverse the flow depending on the pressure.