OSO Unvented water tank - Pressure issues

[jonstatt]

I have an OSO 210l indirect series 20 water tank. In the last 6-12 months it has developed some symptoms

1) When the hot water is really hot, it affects the pressure from the cold water. This can be particularly seen if I flush a toilet, where the cold drops to practically nothing while the hot remains high pressure. While you would expect some drop on the cold, the drop has become much more severe

2) The pressure from the hot water is initially stronger then reduces down after flowing for about 60 seconds or so to match the cold pressure


There is no leaking to the tundish right now although I have had to recreate the air bubble every 6 months or so to prevent a cold dripping.

My first thoughts are the pressure reducing valve and pressure relief valve. I have opened the pressure relief valve and there was quite a build up of green calcium debris in there. This seems to have improved things.

For the life of me I simply cannot get the pressure reducing valve cartridge open. Here is a picture of it. You see it has a massive 50mm nut at the bottom. I have used the tool I have also pictured here to try and undo it. I have used all the force I can muster and it will not budge (the tool is not slipping) and I am trying to undo it in an anti-clockwise direction (i.e rotating the handles of the tool from the left side to the right). Am I trying to open this the wrong way? I am probably being an idiot with this part.

 

[Dan Robinson]

Call a professional.

These devices are not for DIY'ers.

Let alone ones that don't know how to undo a nut.


Sorry, but its for your own good.

 

[jonstatt]

Call a professional.

These devices are not for DIY'ers.

Let alone ones that don't know how to undo a nut.


Sorry, but its for your own good.

Believe me I do know how to undo a nut! But this was the only tool I had that would open up to 50mm. I have also installed a complete EVOHOME system for both water and heating without any issue and done plenty of minor plumbing jobs like changing tap fittings etc. So I am not dim! But I just wondered if this pressure reducing valve had a trick to opening it! Or perhaps the nut has been over-tightened when installed or even has a reverse thread!

More importantly I want to understand if the issues I am seeing are even related to these valves or some other issue.

P.S I have learnt to do things on my own these days after being ripped off by a couple of plumbers in Hertfordshire/UK who think people in this area have more money than sense.

 

[Dan Robinson]

Call a professional.

These devices are not for DIY'ers.



I hope you wired your Evo up correctly for hot water otherwise you might have made a potential bomb.


Only those competent to work on unvented cylinders should be playing with safety devices. Hydraulic or otherwise.



I say again.

Call a professional to look at this problem and check your work.

But what do I know? I only do this for a living

 

[jonstatt]

Of course. I wired the tank thermostat in series with the EVOHOME one so that the high limit cut-off is still in place. There is no bomb here.

 

[Dan Robinson]

P.S I have learnt to do things on my own these days after being ripped off by a couple of plumbers in Hertfordshire/UK who think people in this area have more money than sense.

Irrelevant.

 

[Dan Robinson]

Of course. I wired the tank thermostat in series with the EVOHOME one so that the high limit cut-off is still in place. There is no bomb here.

Still doesn't mean you got it wired correctly.


But hey what do I know? I'm only talking to some one who can't undo a nut.

 

[jonstatt]

Of course. I wired the tank thermostat in series with the EVOHOME one so that the high limit cut-off is still in place. There is no bomb here.

Still doesn't mean you got it wired correctly.


But hey what do I know? I'm only talking to some one who can't undo a nut.

I am not quite sure what your beef is here. I am a quick study and practical. I like to learn about things and do as much myself as I can. I studied very carefully before installing the EVOHOME and talked to other forum members who were keen to share and had spoken to OSO about where to install the temperature probe etc. I was warned what to look for in terms of safety risks , such as keeping the original thermostat in place and I followed all such precautions. I then validated the install by ensuring that the built-in OSO thermostat still had the ability to stop the circuit thus closing off the zone valve and the boiler (After pump over-run). I am confident it is correct. I even validated that the probe reading was the same as the built-in thermostat so I know I got a good install of the probe part too.

And surely for someone like me, cleaning out a pressure reducing valve cartridge should be fairly straightforward! Like I said, I have never had any issue with any nut before...your insults are not doing any good to give a good name to your profession in the area...you are just confirming my lack of confidence and trust in the trade.

And like I said earlier...I would like some information on likely causes of the symptoms I am seeing. Because of my distrust at least I would be armed with the right information if I do eventually call in a professional.

 

[Dan Robinson]

I am not insulting you.

I am pointing out that undoing a nut is not difficult.

If you find it insulting I would politely suggest that is down to your own inadequacies. Perhaps I should take your insinuation that plumbers are all rip off merchants? Especially those who have "Hertfordshire" as their location?

You can confirm and corroborate all you like. Doesn't mean to say that it is done correctly.

Have had to rectify plenty of work over the years that was assumed to be correct by someone who thought they knew what they were doing.


And who ever said cleaning out the cartridge would (or wouldn't) fix the problem?

 

[Dan Robinson]

And like I said earlier...I would like some information on likely causes of the symptoms I am seeing. Because of my distrust at least I would be armed with the right information if I do eventually call in a professional.

The assumption that you would be the only person reading this advice is somewhat typical.


These are controlled, dangerous appliances and require a competent person to work on them.

 

[jonstatt]

I am not insulting you.

I am pointing out that undoing a nut is not difficult.

If you find it insulting I would politely suggest that is down to your own inadequacies. Perhaps I should take your insinuation that plumbers are all rip off merchants? Especially those who have "Hertfordshire" as their location?

You can confirm and corroborate all you like. Doesn't mean to say that it is done correctly.

Have had to rectify plenty of work over the years that was assumed to be correct by someone who thought they knew what they were doing.


And who ever said cleaning out the cartridge would (or wouldn't) fix the problem?

Of course not all plumbers are rip-off merchants...just I have had some bad local experiences in the past few years which caused me to want to be more self educated and do more things myself. If you knew more about the type of behaviour I have experienced I think you would understand.

Like I said I have undone plenty of nuts in my time, but this one requires a wide jaw and perhaps I am just not using the best tool for the job and so thought someone might point me to a better one. For all I know the nut is cross threaded or has been over tightened and perhaps I am just not strong enough!

 

[igneous]

Listen to Dan.

I might as well burn all my certificates because they are aparently pointless.

 

[igneous]

I've cooked plenty of meals, doesn't make me a chef

 

[jonstatt]

Listen to Dan.

I might as well burn all my certificates because they are aparently pointless.

Of course not. But what is wrong with someone bettering themselves and educating themselves? Many people wouldn't want to do your job and will happily call out a professional. And of course if I was getting a whole heating system or water system installed, I would never do it myself. But troubleshooting and cleaning out a valve should not be beyond my limits. And doing so does not take away from your skills or qualifications. I am very aware of the dangers of unvented cylinders which is why I would only venture as far as cleaning out a valve or restoring the air bubble etc.

And you say about cooking meals doesn't make you a chef. Sure, but at least there are many chefs willing to share their recipes!

 

[Madrab]

The regulations (law) state that only a competent person can work on un-vented HW systems and their associated safety systems. In the HSE eyes, competence can only be asserted by individuals passing and obtaining the relevant qualifications, very similar to the rules governing gas work. Therefore if anything did happen and individuals were injured, as you don't have the qualifications, you would be criminally responsible.

I and the others are not trying to be cheeky or insult your intelligence or even having a go at your proficiency, ability or the right to learn and beter yourself, that's the rules & regulations plain and simple and therefore the law I'm afraid and what everyone else is saying!