Combi boiler losing pressure, drain dripping, pressure 3.5bar.

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I have a Baxi 105e combi boiler, around 10 years old. Does a good job of warming the house but the pressure drops fairly regularly, and I have to top it up to 1-1.5 bar at least weekly.
I noticed a slight weep and a bit of rust around where the heating return is and assumed it was that. However today I have had the heating on and witnessed hot water dripping out of the 15mm drain outside. The pressure is above 3 bar when it is running.
I've been having a mooch on the internet and read about a pressure relief valve possibly at fault, is this a possibility? Or perhaps it is doing its job and dumping the water as the pressure is so high. Is the fault elsewhere, whatever is causing the high pressure?
Any advice? TIA.
 
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Been having a read about the expansion tank. Is it worth trying to blow it up first with a bike foot pump. If I do have to change it, is it something I can do myself? Industrial electrical background.
 
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The expansion vessel may just need re charging. When was the boiler last serviced ?
 
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About 2 years ago. From what I have picked up looking at this issue in the last few days I would say that part of the service should be ensuring the Expansion vessel pressure is correct, although I am not sure if he did that.
 
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Unfortunately some " servicing" is sadly wanting.
Yes ,you can do it yourself , however you don't just connect a pump ,and start pumping. The system pressure has to be relieved and a drain cock left open whilst you pump air into the EV . The pump should have a pressure gauge so you can pump it to the correct pressure ,as applicable to your boiler.
 
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Had heating on tonight for about 2 hours. Just looked at the pressure now it has been off for a while and its down less that 0.5 bar, and a wet patch beneath the drain pipe.
Following up the replies on here, I've looked on youtube for examples of recharging the vessel. I believe that you isolate the boiler electrically, close the flow and return valves plus the cold water inlet. Drain off the boiler and reinflate to just above 1 bar.
Will try tomorrow.
Thanks for the help.
 

DP

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It's the expansion tank has failed

Fit a new one will be fine after

Why do you think that is the case? One needs to check if the diaphragm is ruptured before going down that path
 
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probably just the expansion vessel needing charged, you have to do it correctly though, you need a drain point open as you charge it, the pressure releif valve (what you call a drain ) might need changing if it has been constantly activating
 
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One way to check if expansion vessel is faulty Is to take of the plastic cap and push finger on valve, if water comes out then the rubber diaphragm has gone inside expansion vessel. If it’s a pain to change expansion vessel inside boiler then you may want to think about fitting a new expansion vessel externally and leaving the old one in place, this will be fine if that is what’s wrong with it.
 

DP

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One way to check if expansion vessel is faulty Is to take of the plastic cap and push finger on valve, if water comes out then the rubber diaphragm has gone inside expansion vessel. If it’s a pain to change expansion vessel inside boiler then you may want to think about fitting a new expansion vessel externally and leaving the old one in place, this will be fine if that is what’s wrong with it.


Some expansion vessels will allow small quantity of water to migrate to air side. If vessel holds pressure, it is fine. If it does not when being pumped, replacement is the way to go
 
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Just an update. Searched for the expansion tank and it is sandwiched between the back wall and heat exchanger. It is a baxi 105he, looks a pig to change if I ever have to. Took off the bar across the top, to access the valve. There was a little air in when I pressed the centre. Inflated it to 1.1 bar with drain open,using tyre gauge to check. Boxed it all up. Pressurised to 1.3 bar. Runs OK round 2.1 bar, with very little coming out of drain. More importantly after it has cooled down, the pressure is still over a bar.
Can't believe that this isn't included in a service. If I left my bike tyre in a garage for 10 years, I would expect it to lose air.
I still have a weeping connection at the bottom which causes pressure drop over time. Will get it serviced and ask him to look at that at the same time.
Thanks to all for the advice.
 

DP

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Just an update. Searched for the expansion tank and it is sandwiched between the back wall and heat exchanger. It is a baxi 105he, looks a pig to change if I ever have to. Took off the bar across the top, to access the valve. There was a little air in when I pressed the centre. Inflated it to 1.1 bar with drain open,using tyre gauge to check. Boxed it all up. Pressurised to 1.3 bar. Runs OK round 2.1 bar, with very little coming out of drain. More importantly after it has cooled down, the pressure is still over a bar.
Can't believe that this isn't included in a service. If I left my bike tyre in a garage for 10 years, I would expect it to lose air.
I still have a weeping connection at the bottom which causes pressure drop over time. Will get it serviced and ask him to look at that at the same time.
Thanks to all for the advice.
But it is, pressurising the EV is 1st thing any good service guy does.
 
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The last one provided a checklist and pressurising the expansion tank wasn't mentioned. Perhaps I need to get someone different in the future.
 
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