Has my hot water cylinder coil broke?

[Dave18183]

Gauge pics

 

[Ric2013]

I'd be wanting to pressure test the coil at this point, to be certain what is going on. More simply, while the boiler is cold and the cylinder is empty, if you top the pressure back up to 1 bar, does it drop again?

It has been suggested by others that if the cylinder were leaking into the primary circuit (boiler water), the pressure would be over 3 bar and the PRV (on the boiler) would blow. But we don't know what the OP's mains pressure is: it might not even be as high as 3 bar (can be as little as 0.7 Bar).

Also, could the OP please run a bathful of COLD water? This would give us an idea of the quality of the mains water entering the house.

 

[Dave18183]

I'd be wanting to pressure test the coil at this point, to be certain what is going on. More simply, while the boiler is cold and the cylinder is empty, if you top the pressure back up to 1 bar, does it drop again?

It has been suggested by others that if the cylinder were leaking into the primary circuit (boiler water), the pressure would be over 3 bar and the PRV would blow. But we don't know what the OP's mains pressure is: it might not even be as high as 3 bar (can be as little as 0.7 Bar).

Also, could the OP please run a bathful of COLD water? This would give us an idea of the quality of the mains water entering the house.

Thanks for your reply Ric2013.

That is the thing that confuses me. Couple of people on have said the boilder pressure increase if the coil was perforated in the unvented indirect hot water cyclinder/tank. Two local plumbers Ive spoke to have suggest it would decrease.

cold water bath picture just run attached

 

[Chuck]

Couple of people on have said the boilder pressure increase if the coil was perforated in the unvented indirect hot water cyclinder/tank. Two local plumbers Ive spoke to have suggest it would decrease.

There are (at least) two types of leak with different behaviours.

Most of the discussion in this thread assumes a simple bidirectional leak, such as one caused by pin-hole corrosion or a split in copper tube. The flow through such a leak depends on the pressure difference in a symmetric manner. I.e. positive difference causes flow in one direction. Reversing the pressure difference causes flow in another direction.

The second type of leak occurs when joint (solder or welded) fractures but is held normally closed by the springiness of the metal pieces being joined. Such a leak can exhibit unidirectional, aka 'diode', action. I.e. allow flow in one direction, in this case from CH to DHW, but not vice versa.

The second type is less common than the first type and can give rise to some puzzling behaviours.

Anyway, I suspect you have a 'second type' of leak. To diagnose, you either need to put tracer dye into the CH water or pressure test the cylinder coil.

 

[Dave18183]

Thanks Chuck, thats interesting thoughts. It doing my head in!

Afte a bit of a tank refill and emptying again I feel like it should be empty now but its still draing with not quite clear water and a very slight noticeable chemical film on the stop of the water.

Getting noises as it goes. Is this the sound of the coil draining into the tank?


Pressure has continued to drop at the boiler thought slowly. Down from 0.4 bar earlier to just over 0.2

 

[ShaunCorbs]

Fill the boiler up to 1 bar once the cylinder has stopped draining does the cylinder start running with water

 

[Dave18183]

Fill the boiler up to 1 bar once the cylinder has stopped draining does the cylinder start running with water

Thanks.

Currently the cyclinder is still running at a slow pace into the washing up bowl which I keep emptying. Water slightly browned.

To fill up the boiler I guess I just need to open the cold water isolation above the tank (which will fill the tank again) but t will also provide water to the filling loop which is above the tanke (which I need to use to raise the boiler to 1 bar) Is that right?

 

[ShaunCorbs]

Have you got a pic ?

 

[Dave18183]

Have you got a pic ?

Here you go. Thanks

 

[Chuck]

Currently the cyclinder is still running at a slow pace into the washing up bowl which I keep emptying.

Open a hot water tap to allow air in and help drain the pipework. (The glugging sound on the video is the clue that this is needed.)

 

[Dave18183]

Open a hot water tap to allow air in and help drain the pipework. (The glugging sound on the video is the clue that this is needed.)

Ive had the nearest hot tap open througout the drainning

This slight flow that has been draining out from a short refill has just finished. Took a long time, and cant help but feel more water than what I let back in the tank just to wash ip up again.

 

[Dave18183]

Fill the boiler up to 1 bar once the cylinder has stopped draining does the cylinder start running with water

Ive tried tried to do this. Went abit past 1 bar, but in using the filling loop water was coming into the tank anyway and yess it did drain down (hot water tap was open not sure if it was meant to be)

 

[Dave18183]

I have refilled the tank completely now, its full but some pressure is returning to the boiler 0.2 Bar to 0.7bar, the filling loop valve is shut.

How can the CH pressure increase by filling the DHW tank if they are separate systems? Is this not a sign that there is A breach i.e. coil split/perforated

 

[ShaunCorbs]

So you filled the ch sys to 1 bar then opened / left open the cylinder drain and water came out and the boiler pressure went down ?

 

[Dave18183]

So, the tank refill was complete, central heating and hot water


I’ve still not opened the filling loop to fill the boiler/central heating system but the boilder pressure

So you filled the ch sys to 1 bar then opened / left open the cylinder drain and water came out and the boiler pressure went down ?

yes, as above. Ive tried tried to do this. I did go a bit past 1 bar in filling back, but in my configuration, opening the filling loop and the col water valve (on the picture I put that you asked for) water is also going into the empty tank at the same TimE (not sure that is what you intended.

I began to drain the tank/cyclinder, opened a hot water tap to let air escape, drained the cylinder totally and the pressure at the boiler dropped to as it was ealrier in the day when emptied (about 0.2 bar) the water was a little discoloured.

 

[ShaunCorbs]

Right don’t fill the heating system up remove the flexi link

open the cold water to the cylinder and vent eg fill it up

does the heating system pressure rise

 

[Dave18183]

Ive then after above, refilled the cyclinder/tank fully with the filling loop valve (to the central heating) closed. Boiler gauge was at 0.2bar.

The tank was full and I left it for a couple of hours. Boiler i.e. central heating pressure is now just short of 1.8 bar

How can the CH / boiler pressure increase with the filling loop valve closed? Other than filling slowly through a coil breach?

Ive just opened the filling loop just now and there was no inrush of water at all.

ive turned the heating and hot water back on now for the first time all day

 

[ShaunCorbs]

Remove one side of the filling loop is there water coming out ?

 

[Dave18183]

Remove one side of the filling loop is there water coming out ?

So with DHW tank and CH seemingly fully filled now, remove the loop a the blue circle with the filling loop valve closed (as in the picture).

 

[ShaunCorbs]

Correct right nut on the flexi remove slowly encase there’s water there

 

[Dave18183]

Correct right nut on the flexi remove slowly encase there’s water there

Ok. Done. No drips or flow

turned the HW and CH off before I did it

 

[ShaunCorbs]

Is the water back onto the cylinder?

 

[Dave18183]

Is the water back onto the cylinder?

Yes fully open. Here is what you see. And the cold water isolation fully open (spindle extended) at the back

 

[ShaunCorbs]

Then yes I would concur that your hot water cylinder has failed somewhere

 

[Dave18183]

Then yes I would concur that your hot water cylinder has failed somewhere

Ok thankyou. For my understanding. Can you help me understand how what I did helped you determine this? On it own or with something else I have done this far. Thanks