To leak or not to leak - that is the question!

[Milleniumaire]

Sorry, this may seem like a strange question, but it's based on my observations over the last week while I've been having problems with my boiler.

When the boiler has been turned off for a while and the CH water cools down, I've found a number of small leaks around the boiler area:
- 2 port valve leaking from the top, where it inserts into the actuator head. Telltale sign was water dripping from the bottom of the valve
- Water leaking from magnaclean cap
- Small drops of water leaking from auto venting cap on top of the pump

However, for the last 3 days, the heating has been behaving and I have not seen ANY sign of leaks from these same places. Whenever I've checked, the CH has been on, so the water in the pipes will be hot.

Does cold water leak more easily than hot water?

I'm thinking that when my boiler cuts out due to lack of pressure and I wake to a cold house, this is when I tend to notice the small leaks. The water in the pipes is cold and standing i.e. not being pumped around.

Most of the time, when the boiler is working, the water in the pipes is hot and being pushed around, but then there's no sign of water leaking out from the mentioned places! I would have thought that hot water under pressure would be more likely to be forced out through a leaking valve than standing cold water.

Why does my CH system only appear to be leaking sometimes?

 

[ianmcd]

when the system water is hot the boiler components are also hot and everything expands , when the system water is cold all the component contract and can start to leak, sometimes works the other way around as when the system water is hot it is under a slightly greater pressure

 

[dilalio]

There are cold leaks: when materials contract and hot leaks: when they expand!
During operation of your system, there is a point at which falling or rising pressures interact with expansion or contraction of materials (threads, o rings etc) to manifest in leaks!

Blockages in system and pressure from pump overrun or vent pipe can lead to this.

 

[dilalio]

when the system water is hot the boiler components are also hot and everything expands , when the system water is cold all the component contract and can start to leak, sometimes works the other way around as when the system water is hot it is under a slightly greater pressure

Bloody hell Ian... you beat me to the post button That'll teach me to go to the fridge for another cold one

 

[ianmcd]

Bloody hell Ian... you beat me to the post button That'll teach me to go to the fridge for another cold one

No six nations this weekend mate so nothing else to do ha ha , enjoy your beer I am having a lovely Rioja before she that must be obeyed gets in demanding sex again

 

[dilalio]

I have lots of jobs that I need to do around the house but, following a production meeting with myself earlier today, it was decided that all the relevant works permits and RAMS were not in place; plenty of beer in the fridge however, so works have been postponed to a later date!

SWMBO will not be demanding sex off me when she returns!
I however, will be demanding pizza!

 

[dilalio]

OP: rereading your post, indicates your system is sealed???
Scrap my vent pipe comment but check gauge during operation and also ev charge.

Edit: oh, and bypass

 

[Milleniumaire]

Thanks guys, I had forgotten about expansion of the pipes etc and was only considering the state of the water. I guess depending on the materials, the heat will expand joints and cause a tighter fit. Having not seen any sign of the leaks I saw earlier in the week, they re-appeared today as the warmer weather caused the system to cool down (it uses weather compensation).