Decent video. Confirmed what I already thought about dropping the system water pressure to zero before charging the vessel with air, but added that you need to keep a valve open for water to escape WHILE charging. Good point! Basically my understanding is that an expansion vessel or any water / air pressure vessel needs to be able to empty itself of water while you're charging it with air so that you're measuring the pre-charge pressure with it full of air.

"How to recharge an expansion vessel". Good thing to know. Have gone to many jobs when all what was needed was a recharge of the expansion vessel but the person before hadn't seen this video and the poor customer had to suffer.

Excellent video Derek like always very useful information regarding the expansion vessels, thanks for the time and effort taken in making the video. Derek still looking forward to the video on how to service and unvented cylinder, please if you can do a video on that it will be appreciated. Thanks. 😃😃👍

Nice video . We do similar, but ... 1. We tend to replace the shrader valve, for 5p not worth waiting to find it's leaking. 2. There is often a little water on the air side, I know you know that, but worth pointing out. We had time served good heating engineers working for us, I collected 10 expansion vessels that had been replaced, I put them on test with new valves and found 8 were perfectly fine.. on the whole they are pretty reliable and in most cases if they are falling its system design or high flow temps especially on oil combi's. Keep up the good work, all the best for 2022

Thanks Derek great video 👍

Thanks Derek

brilliant video

Thanks for your videos

Just something I've thought of: if you can't get any air to go into a pressure vessel it might be because the air side is so full of water that there's no space for air. I had that once when I was fixing my house water pump which has a small PV. Couldn't figure it out at the time, but that might've been the reason.

Sound advice sir.

Good video Derek, thanks. The video in your link is not the vessel-sizing video, it's the 'What's inside the boiler' video. Very interesting and informative.

Happy New year Del🍾🍾🥂🥂

I always find it good practice to put a little silicone grease on the Schrader valve. It helps the valve seat and keep the Schrader valve rubber supple. I do think baxi undersize those expansion vessels. 7 litres is a bit small. Great tutorial as usual Dez.👍

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Hey Derek. Great video as usual. Just have a couple of questions. 1) how did you get to the figure of 8 litres for 150 litres of system water ? 2) why did you add another 0.2 bar to the charging amount? Apologies if I just missed the detail in the clip I watched it more than once. Thanks in advance. Mac

Hi Derek. So, if you can't check the expansion vessel pressure accurately while the system is full of water, as it will always be unless some serious work is being done on it, then that explains why Gas engineers never check them. Right? I asked my engineer to check mine, but I realise he didn't.

@ 2:37 Ergo... Even if Gas Safe Registered on paperwork... Dose NOT make them competent;... if they FAIL to check expansion vessel;... where ever fitted in the system...

Why the extra 0.2 bar?

Shouldn't use PRV to drain a boiler. Asking for trouble

This video is typical of people who work in training centres but not in the real world. Never touch the iso valves and never open prv unless you have too. 99 times out of 100, these components will leak if disturbed and cause the customer more money.

ta