How To: Boiler Losing Pressure

In this video I attend a Gas boiler losing water pressure. I show you how I check and repair the most common issue related to pressure problems. The expansion vessel on the boiler has a simple job of absorbing the excess expansion of water in your heating system when it is on and running. If the vessel doesn’t do this the pressure relief valve will begin to leak. This will cause overnight pressure loss within the heating system. Basically every hot and cold cycle will cause the pressure in the boiler to drop. This will lead to topping up the pressure every day. If the pressure gets low enough most boilers will fail leading to no heating and hot water.

See the links below for some of the tools I use in this video. Only quality make the list.

This channel is to help engineers fix boilers. I try and teach boiler repair for the betterment of the UK gas industry. The better we are the more work we get.
Common UK boiler brands such as Vaillant, Ideal, Worcester and Baxi all have more obscure models and this is one of them.
Unlike the USA, our boilers are all high efficiency and more technology makes for harder diagnosis.
For videos on Burnham, Weil-Mclain, Peerless and Lochinvar find a US Channel.
I typed all that for better keyword and YT ratings. Lets see!!

Here are a few affiliate links to some of the stuff I use everyday. This is quality stuff and I have found the best prices possible

Puncture Repair Kit
https://amzn.to/3HhiB5H

Bahco Spanner
https://amzn.to/42vhvgr

Budget Friendly Martindale multimeter
https://amzn.to/3SiV4X2

Fluke Multimeter
https://amzn.to/3HKiMXl

Knipex Grips
https://amzn.to/49jng39

8mm ratchet spanner
https://amzn.to/3HM5Xfq

10mm spanner
https://amzn.to/49EGzUT

Kline Backpack
https://amzn.to/3UsqaON

All right here we are this boiler is on just over half a bar and the heating is off we’re going to put the heating on now and we’re going to see what happens and if your boiler does this same thing then you need to get it sorted otherwise

It’s going to break down on you very soon all right so I’ve just put the heating on the boiler’s lit and running and we’re going to give it 5 minutes and we’ll see what happens all right here we are it’s after about I say 10 minutes so we’re still lit and

Running and we’re at 2 and 1/2 bar over 2 and 1/2 bar okay cuz when you heat water it expands and the expansion vessel on the boiler is meant to absorb that um that expansion the amount of expansion there is determined by two things the amount of water and the

Temperature you heat it to so if I was to whack this temperature up this is down low now to save the boil cuz I saw this a week ago I saying I turned it down and said i’ have to come back soz I didn’t have any tools so if we turn that

Up and give it another few minutes that’s it’s going to get higher and higher and higher and higher okay as that temperature of the water gets hotter that pressure will just keep Rising let me see if you can actually see the needle moving up yeah you can let me try and not Shake

Here we go yeah just by the temperature increasing the pressure’s going up now once it gets the free bar the boiler will let the water out okay and then your boiler will not work the next day cuz it will let all of that pressure out so now I’ve turned it off I’m going

To go I’m just going to turn this down I’m going to turn it off inside as the water cools down that will go back down and uh one tip for engineers out there if you ever go with a boiler and it’s got say two bar and it it’s been running

You think nothing of it and you drain it but when you drain it you get you know this much water in the bottom of a bucket that is that’s telling you the expansion missel full of water and failed because the expansion vessel the water should go into it as it expands

And then when you drain it it all comes back out of it so if you got an 8 lit vessel you should get say 6 L out of it right so when I drain this boiler now in the bottom of my bucket it I reckon I’ll

Have 2 to 3 in of water that’s it maybe even less than that and that will be all that pressure in the boiler in my bucket so let’s get set up for that we take this off undo them two screws get access into the boiler take this cover

Off okay so the boiler’s turned off the pressure is dropping down here as in the power off to the boiler pressure slowly coming down as it cools I’ve got a bucket there and I’m going to try and drain it from here and fortunately my hose isn’t long enough we

All have that same problem look how quick the pressure is dropping look how much water’s in the bucket right now so I’ll open this up a wee bit more one and a half bar and we probably got an inch of water one bar this vessel’s not completely flat it’s got some

Water coming out yeah but you can see that’s not much water in that bucket I don’t to open this too much and have it spray everywhere but so I let this finish draining and then we’re going to get up here and find the uh there it is the connection

For the expansion vessel the uh the Shader valve right there’s a little bit there let’s see how much pressure is actually in this vessel we have to leave this open while we’re doing this cuz any if the vessel’s flat and it’s full of water okay you have to have an open point on

The system so you can pump it and the the water will leave the vessel and come out into this bucket so actually probably got about 3 in of water in there it’s not bad but you’d usually expect it to be sort of up here when you’re draining a

Boiler you know good 10 L comes out of them let’s get on that vessel I make my life easy by using a c pump it’s on bar and I like to put about 1.2 in and that’s where we’re at 1.2 okay let me get this connected

On tank got that on and we are showing Zero let’s pumped it up as the water leaves that pressure may go down okay and it it is see that that’s the water leaving the vessel that’s where you need the open Point okay we’re down to half a bar now see the bucket’s filling up the pressure gauge has gone up that’s

Cuz we’re compressing all that air in the vessel and the water is has hasn’t left the boiler quick enough okay oh this is not good if you see lots of bubbles like this it could be that your vessel is completely failed and the air that you’re pumping in up here here

Is making it way down that copper pipe at the back there a little tiny one going up the back and is managing to come out of this hose don’t think that’s the case here but it could be let’s see if it stops our pressures remain stable in the

Vessel the air vent sucking in now at the back there but that has stopped gurgling down there we’re holding at 1.2 bar all right look how much water’s in that bucket now that’s all the water that shouldn’t have been in that expansion vessel okay so that’s that’s you know

Where you’d expect it to be so still at 1.2 bar it’s time to close this disconnect this up here don’t know if you can see but here we go okay so the sh the valve has a problem okay the core is the core is leaking all right so we’re going to have

To open this cuz we’re going to have to pump that up again and I’m going to go and get a cal Trader valve Cal from the van so if you’ve seen my video on puncher repair you’ll know I have this kit in this kit is also where mark cores are in there get

That there’s the removal bit there I’m going to unscrew that and I’m going to I’m going to unscrew that on the boiler and replace it with that one and these are just a standard trade of valves that you would get on a car tire or a bicycle

Tire so I’ll get the old one out put one of them in hopefully this tool will bit here yeah just just okay so I will say you can sometimes get these working again bit of WD40 and give it a good finger in but doesn’t always work and

Uh I just want to get this done so very awkward this I’m leaning in a corner and I can’t get there we go got it out I can’t get get my fingers in there cuz the flu’s in the way anyway there we go that’s the shrade of Val caught out I do

Uh use the universal Lube of spit on them simply because that’s what I’ve got to hand right now and the van is parked a long way away that got very tight very quick I’m hoping that’s all right one 1.2 bar here we come so ldf a bit of leak detection

Fluid on that this one I like and the reason I like it is because you buy bolt fluid and you can top it up um I do have the aerosols I do use the aerosols but I do prefer this type that does not appear to be leaking anyway let got

A yeah no big bubbles coming out get a cap on that get this B filled up and I’ll show you the result of topping up an pumping up an expansion vessel correctly I want to just mention one other thing there is a seal inside these you see there’s a Rubber seal SE around

The outside of that point that’s a Rubber seal it’s a bit dirty in this one so if they let by a little bit you can tighten these on to get people by if you haven’t got core um but let’s close this for the second time now give them a flick sometimes the gaug

You stick okay so if this pressure has reached three bar okay because you haven’t noticed that you’re having the problem the safety valve the pressure relief valve which on this boiler is right at the back there pretty awkward not as awkward as some n worsters though um you will

Have a leak dripping outside so on this boiler here is cu this is an out house it just drips on the floor but you will probably have a pipe go through the wall in your kitchen and then outside it will hook back to the wall all right that’s

So if it sprays hot water out it runs down the wall if that’s dripping then that safety valve they don’t usually seal back up once they’ve started dripping that will need to be replaced or serviced all right um you’ll need an engineer for that you’ll all need an

Engineer for all of this so this is a 24i junior there you go you can see there’s a flame in there so it’s back on and running so to check that this has worked we’re now going to run this for 5 or 10 minutes now let’s say after

10 minutes if we haven’t gone above you know 1 and 3/4 we can be quite comfortable that this is good all right we’ll turn that right up and that vessel is doing its job all right so I’ll give it 10 minutes I’m going to put it back

Together while I wait um cuz I’m assuming it’s okay and uh and I’ll get back to you in 10 minutes we’re just below 1.5 bar obviously the temperature is much higher than it was uh the customer I had turned it previously down to less than that I’m going to leave it

In the dot there that boiler is done all right so tips to stop your boiler breaking down due to pressure loss number one check for leaks cuz that will give you a pressure loss number two notice when your pressure begins to fluctuate if you notice it early the

Safety valve on the boiler the thing at the back on this one won’t start leaking so if you notice that pressure early get an engineer out he can pump that vessel up number three this is a tip when you’re recharging or pumping up an expansion vessel you have to have an open point

You need to have the drain Point open so that when you pump that up the water can leave it otherwise you get a false reading on your gauge as in the gauge that you’re using to Pump It Up and you won’t put enough air in it okay a lot of

Engineers newly newbies don’t realize that number four check it afterwards turn the boiler up I mean even run it on Max get it as hot as you can as quick as you can and check you’ll know if you fixed it now if you’ve done this this is a big tip if

You’ve done this and when you put this on and run it on Max this pressure goes Sky High the little copper pipe at the back or the little flexible hose which is more common is blocked okay if you look at my uh heat line Caprice video that I

Made last year I’ll show you how to deal with a block expansion vessel pipe okay it’s there are some really important tips in that video if you get it wrong you’re going to get absolutely filthy water all over a customer’s house running sweet as a nut now it’s definitely time to go

Because look at them clouds look at it w it’s ominous absolutely ominous tip number one when dealing with expansion vessel problems or pressure losses check your pressure more regular be aware of what’s going on if your pressure is going Sky High you got an expansion vessel full if you’ve

Got an expansion vessel full it could be leaking out of your safety valve okay check outside for the pipe that hooks back to the wall and make sure that’s not leaking that’s tip number one tip number two if your pressure is going skyh high if you can notice that before

A problem you can get it rectified easily tip number three make sure the drain point is open while you’re pumping the expansion missile that way you can allow the excess water that’s built up inside it to escape tip number four check your Shader valve make sure once

You finished the job you spray that with some sort of soapy water solution Leak Detection fluid something like that to make sure that that is not leaking otherwise you’ll just be doing the same thing again in a couple of days okay last but not least tip number five make

Sure you check it afterwards you run your boiler up to a really nice and hot temperature to get maximum expansion make sure the expansion vessel can cope with maximum temperature all right I will catch you and see you on the next one