Odd hot water cylinder issue

IRLConor

I've a weird problem at the moment where neither my immersion or my gas boiler is able to heat the water in the hot water cylinder. The water goes from cold to tepid/lukewarm but never gets hot. The setup isn't that complicated, it's like this:



Gas on its own, immersion on its own or both on together. Nothing heats it. Now, the two pipes from the boiler circuit are roasting hot, so I'm assuming heat is getting into the cylinder (plus the immersion sounds like it's working) so the only possibilities I can think of are:

1. Hot water going back into the cold input. This is implausible because:
   1. That pipe is cold enough to have condensation on it.
   2. As far as I know, it comes from a tank 3 stories above me (apartment building) so there's enough pressure to resist hot water flowing back through it.
2. A leak somewhere which is drawing off the water faster than it can be heated. I don't think this is plausible because either we'd notice a bunch of water under our flooring (wood floor on concrete - squelch!) or our neighbours would have enough water coming down to cause them to notice and complain.
3. There could be a continuous flow of water through the cylinder which is magically draining out of the apartment in such a way that it's not causing a mess (i.e. going out into the waste water system somehow).

Option 3 is the only vaguely plausible option, but I can't for the life of me figure out where the water could be going! I'm going to shut off the cold input (to prevent any flow through the cylinder) and try and heat the water. If it's hot, I'm going to assume option 2 or 3 is true.

Is there anything obvious that I could be missing?

Micky Dolenz

Is there condensation on the cold feed inlet pipe? If there is, it shows that very cold water is passing through the pipe,which would point toward constant flow. Water in that pipe should be static normally and would not condensate.



What time of heating system do you have? sealed or vented? is a hole in the heating coil a possibility?

IRLConor

Micky Dolenz wrote: »

Is there condensation on the cold feed inlet pipe? If there is, it shows that very cold water is passing through the pipe,which would point toward constant flow. Water in that pipe should be static normally and would not condensate.

Hmm, that makes sense. There is quite a bit of condensation on that pipe.

Micky Dolenz wrote: »

What time of heating system do you have? sealed or vented?

I hate to sound like a noob, but what exactly is the distinction?

Micky Dolenz wrote: »

is a hole in the heating coil a possibility?

Inside the tank? Perhaps, but wouldn't that lead to warmer water?

Avns1s

Is there a stopvalve on that green pipe somewhere in the hotpress?

If there is, turn it off and see if the top of the cylinder heats then.

To me, it seems like there is a flow through the cylinder pointing to a leaking pipe feeding one of your hot taps or a leaking tap.

Micky Dolenz

What type of gas boiler have you? Do you have a small tank in attic?

IRLConor

Avns1s wrote: »

Is there a stopvalve on that green pipe somewhere in the hotpress?

If there is, turn it off and see if the top of the cylinder heats then.

To me, it seems like there is a flow through the cylinder pointing to a leaking pipe feeding one of your hot taps or a leaking tap.

There's no stop valve on the green pipe, but there's one on the blue. Stopping that should have the same effect, right?

IRLConor

Micky Dolenz wrote: »

What type of gas boiler have you? Do you have a small tank in attic?

I don't know the type of boiler I have off the top of my head, I'll check when I go home. It only went in a year ago, so I'm not suspecting issues with it. (Also, the radiators work off that and are fine.)

It's an apartment, so no attic. There's a tank on the roof AFAIK.

This problem started happening after clearing an airlock in the blue pipe (caused by works on the roof to fix burst pipes going to some of the other apartments). Before then, we had no pressure in the hot taps at all.

slavetothegrind

is there a chance the expansion pipe is syphoning?

IRLConor

slavetothegrind wrote: »

is there a chance the expansion pipe is syphoning?

If I knew where my expansion pipe is, then I'd check! (But yes, going on my extremely limited knowledge of plumbing that would fit the symptoms.)

SEVERA

Deffo water being drawn away faster than it can be heated i would say you should even be able to hear the water flowing through the cylinder,,, unless you have a thermostatic blending valve on the green pipe which may be faulty, these mix the water to a safe temparature before it leaves to the taps and showers etc if so increase the mix of hot water through this valve by turning anti clockwise normally but it usually is marked on top of the blending valve.

IRLConor

I turned off the cold input (blue above) and I could hear water stopping.

Thanks for the help folks!

Now for the next trick: find where the water's going and stop it!

Micky Dolenz

you have a flat under you? and no attic, so I assume all your systems are pressurised, ie plumbing and heating.

Check outside where your boiler is and ensure that the safety valve isn't letting by. could be a sign of a breached heating coil in cylinder.

IRLConor

Micky Dolenz wrote: »

you have a flat under you? and no attic

Yup.

Micky Dolenz wrote: »

Check outside where your boiler is and ensure that the safety valve isn't letting by. could be a sign of a breached heating coil in cylinder.

The boiler's in the kitchen and all appears fine. So far, luckily enough, the boiler hasn't complained about anything.

Micky Dolenz

IRLConor wrote: »

Yup.



The boiler's in the kitchen and all appears fine. So far, luckily enough, the boiler hasn't complained about anything.

Look outside, where the boiler flue exists.The pressure relief valve will terminate in the same general area, is there any sign of spillage of water there? unlikely but possible.

IRLConor

Micky Dolenz wrote: »

Look outside, where the boiler flue exists.The pressure relief valve will terminate in the same general area, is there any sign of spillage of water there? unlikely but possible.

I had a quick look there, it looks fine and dry.

Thanks again for all your help!

SEVERA

i suggest you get in contact with people who are in apt below you if occupied asap