Loss Of Pressure In Unvented Hot Water System

Joined
4 Jan 2019
Messages
3
Reaction score
0
Country
United Kingdom
I have a Kingspan Range Tribune Unvented Hot Water Cylinder (on 3rd floor) with an Ideal Logic 15 Boiler (on ground floor). Whole system is only 4 years old, as is the house. No obvious signs of leaks anywhere. No water coming about

We put the central heating on for the first time since the summer the other week, and when the radiators weren't heating up, I found the pressure gauge at the expansion vessel to be at 0. I topped up the system with water to around 1 bar, bled the radiators and then topped it back up to 1 bar. Within a day or so the pressure is back to 0.

The water pump looked like it may have had a small leak out of one of the isolation valve compression fittings at some point. Took that off, cleaned it all up and refitted it, no leak there. Took the expansion vessel off, made sure the seal was good there, refitted it and re-pressurised it and the system. Again, within a day or so the pressure began to drop.

Last night I thought I need to now do some process of elimination. I took the expansion vessel off again, and pressurised it to 1.5bar off the system. Left it for 45mins and it had held its charge. I then filled the system to 1.5bar. I have the boiler turned off, with valves 1 & 2 closed (red circle - 2x central heating zones), valve 4 closed (blue circle - hot water) and the water pump isolated (by the valve in the orange circle). The pipe labelled 1 comes directly from the expansion vessel and goes to point 2. So I essentially have the system isolated from the expansion vessel to the valves. Since last night the system has lost 0.5bar.

I'm now confused as to what it could be. I haven't checked the pressure of the expansion vessel yet as I just checked the gauge before I left for work, but seems like its the system is losing pressure rather than the vessel. Could it be the PRV for the expansion vessel? The only other thing is at point 1 on the picture the pipe T's off to two other pipes and disappears into the wall, I have no idea where these go.

Any suggestions would be gratefully appreciated

Water Tank.jpg


Expansion Vessel.jpg
 
Sponsored Links
Joined
4 Oct 2012
Messages
9,116
Reaction score
2,702
Location
East Renfrewshire
Country
United Kingdom
Remove the boiler out of the equation first. Isolate the boiler flow and return and see if it still loses pressure overnight. Is there any water in the tundish/@ the outlet outside?

Oh and please don't put PTFE tape around the threads of anything in your system (pump!!)
 
Joined
4 Jan 2019
Messages
3
Reaction score
0
Country
United Kingdom
Remove the boiler out of the equation first. Isolate the boiler flow and return and see if it still loses pressure overnight. Is there any water in the tundish/@ the outlet outside?

Oh and please don't put PTFE tape around the threads of anything in your system (pump!!)

Would me not closing the isolator valve (orange circle) on the pump take out the boiler?

No water in tundish or outside outlet
 
Joined
4 Oct 2012
Messages
9,116
Reaction score
2,702
Location
East Renfrewshire
Country
United Kingdom
What about the boiler return/Ch system system? You need to locally isolate at the boiler on both flow and return, if the pressure doesn't drop then it's the boiler, if it does then it's not.
Use an adjustable spanner on the 1/4 turn valves if you can, not a screwdriver, less liable to leak.
 
Joined
4 Jan 2019
Messages
3
Reaction score
0
Country
United Kingdom
What about the boiler return/Ch system system? You need to locally isolate at the boiler on both flow and return, if the pressure doesn't drop then it's the boiler, if it does then it's not.
Use an adjustable spanner on the 1/4 turn valves if you can, not a screwdriver, less liable to leak.

The flow and return that come out the top of the boiler don't have any isolation valves on them. It seems my only options for isolation are by the tank (unless I'm not seeing something).

When I returned home I checked the pressure of the expansion vessel (via the Schrader Valve) and it had dropped by 0.5bar, could it be this? No water came out when I have released some pressure from it before. I have had to put the heating and hot water on for a bit now, and the pressure has risen slightly too.
 
Joined
21 Feb 2019
Messages
1
Reaction score
0
Country
United Kingdom
guarantee if theres no visible leaks, vessels ok, then the issue will be with the logic boiler (i think they had an issue on the heat exchanger or something)
i know this because i mainly work on that particular cylinder.

:)
 
Joined
15 Aug 2010
Messages
24,926
Reaction score
11,125
Location
Livingston
Country
United Kingdom
The flow and return that come out the top of the boiler don't have any isolation valves on them. It seems my only options for isolation are by the tank (unless I'm not seeing something).

When I returned home I checked the pressure of the expansion vessel (via the Schrader Valve) and it had dropped by 0.5bar, could it be this? No water came out when I have released some pressure from it before. I have had to put the heating and hot water on for a bit now, and the pressure has risen slightly too.
if you have an expansion problem then the water will be visable in the tundish, place a small piece of toilet paper at the outlet of the tundish and see if it gets wet, or put a bag or balloon over the relief valve outlet outside and see if any water collects, if either does then you have an expansion problem if not, if you can disconnect the condensate out let from your boiler and put it into a dish or bowl or something and turn the boiler off, if you get water coming from the condensate with the boiler off then the boilers heat exchanger has pinholed, and you are correct your boiler doesnt come with isolation valves
 
Sponsored Links
Top