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Megaflo combination valve height

Discussion in 'Plumbing and Central Heating' started by Friday round, 26 Mar 2021.

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  1. Friday round

    Friday round

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    I’d like to carry out maintenance on the combination valve strainer. I’ve seen some videos, but have a question on the low height of combination valve relative to height of the T&P release valve. After draining from the T&P, does it matter that the combination valve is so low? I’m concerned that since it is lower, then water will flow out when I open the valve.
    D39287FE-7868-44EA-BE22-54B3B8CD7428.jpeg
     
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  3. Madrab

    Madrab

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    Unvented cylinders are non user serviceable, it needs a qualified engineer to perform any service work. The only work that a user can perform is to replenish the internal bubble if it has one.

    I think I'd be more concerned about the D1 pipe from the PRV, I need to check but I certainly wouldn't have it installed rising vertically, if the picture's the right way up?
     
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  4. muggles

    muggles

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    As Madrab says, you can't service that yourself, you need to be G3 Registered to work on these. The T&P valve should never be used for draining either. Also, it's installed incorrectly - the cold supply pipework needs to be extended up to near the top of the cylinder, and the pressure reducing valve and pressure relief valve fitted up there. It's not permitted to fit the pressure relief valve with the discharge pipe running uphill. I'm sure your G3 engineer will be able to correct this when they carry out the service.
     
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  5. Friday round

    Friday round

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    I thought the cold water combination valve strainer inspection and clean is maintenance and not G3 required. Directions are on their manual.
    Also T&P drains what’s in the tank out so I don’t get what you mean. Here’s the video

    Thanks for calling out the upward pipe direction. Please point out where in the Megaflo doc that says where the mains, PRV and PRV need to be at the top of the cylinder and the reason. Genuinely want to understand.

    Back to the original question. If I follow the directions in the Baxi video, is the only water that will spill be from the bit of pipe between the PRV and the shutoff valve right below the combination valve?
     
  6. Madrab

    Madrab

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    Invariably the combination valve is located above the level of the HW outlet, it allows maintenance of the valve and it's components and attachments without the need to drain the cylinder down etc. Not sure it's actually part of the G3 requirements or specified by the installers but it's certainly best practice and promotes energy efficiency and minimises the waste of water etc.

    Given where the combi valve is, if the video is followed and drained to the level of the T&P valve then there's still the water from the T&P valve down to the combination valve to go. Depending on what side the NRV is in the combi valve ..... but even then it's not worth the risk ... if the top of that valve is opened then there could be the other half of the cylinder on the floor. That's why the combination valve is best placed at least above the level of the T&P valve, so that's all that's needing drained.

    As far as the D1 relief pipe is concerned then again I'm not sure if it's in the regs, when I get back I'll need to check. The whole point of a relief pipe though and the D1/D2 runs is to allow a free and easy path for the vented/relief water to exit and an upwards outlet is certainly not that.

    The info is in the manual as that's the cylinder's MI's, it's mostly there for the service engineer. Not sure what megaflo you have but pretty sure they usually only have a small one odd page for the user section and cleaning the strainer isn't usually in that section, it's usually under servicing.
    Servicing should be performed by a qualified (competent) person, unfortunately it's the regs as unvented cylinders have the potential to be dangerous.
     
  7. sjmac

    sjmac

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    What sort of ****** fits that valve at the inlet height
     
  8. Friday round

    Friday round

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    Servicing the PRV strainer is under the manuals maintenance 1 pager. There’s several utube videos when searching for Megaflo maintenance with similar setup where the cold water combo valves sit low. It must be ‘those’ G3 engineers. It does seem dodgy and so why I’ve asked the question.
    But to push the question further... the 8 bar Prv can be demonstrated to work properly by performing the air gap replenishing steps or shutting off the cold feed, so with no positive pressure, water escapes from the tank to Prv and tundish or not, right? So, as I’d like to maintain the 3 bar PRV is it really a risk at all and why?
     
  9. muggles

    muggles

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    Do you have the necessary tools and experience to test that it's working correctly one you have finished b̶u̶g̶g̶e̶r̶i̶n̶g̶ ̶a̶b̶o̶u̶t̶ ̶w̶i̶t̶h̶ maintaining it, or are you just going to hope that you've not damaged it in some way?
     
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  11. Friday round

    Friday round

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    @muggles If you’re not going to constructively advise, then what’s the point of responding. Please focus on the discussion. If you’re raising additional points to consider and you have experience in the matter then ok - what tools are you talking about? Otherwise, I know it’s still lockdown put please log off and go outside.
     
  12. fezster

    fezster

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    The T&P valve is much higher up on the cylinder, so that isn't sufficient. Without an isolation valve on the cylinder CW inlet, you'd have to use the drain off valve to empty the majority of the cylinder out and then be left with a small amount of water sitting in the pipe above the pressure reducing valve.

    As these components are for an unvented cylinder, they fall under the G3 regs. However, if you didnt have an unvented cylinder, a pressure reducing valve, pressure relief valve and expansion vessel would all be perfectly DIY-able.
     
  13. ianmcd

    ianmcd

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    @muggles is correct and what you are proposing is not a DIY job, im afraid the HSE trump youtube in this case, being rude to the pros on here seldom gets you the advice you seek, you will get advice but from other google warriors
     
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  14. Madrab

    Madrab

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    We are trying to explain that service work on an unvented or it's components shouldn't be performed by a non qualified engineer. We're not saying it to get your nose out of joint or have any other ulterior motive, it's just the way it is.

    In the Megaflo manual, only the 2 pages from the heading 'Users Instruction' are what a non qualified user can perform. Once it gets to the 'Maintenance' section, it's back to the professional. In the 1st paragraph under maintenance it states that the work should be performed by a 'competent person', in the case of an unvented HW cylinder and in the eyes of the HSE/Law, competency is only proven by obtaining a relative qualification I'm afraid.
     
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  15. fezster

    fezster

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    I tend to stay away from these types of threads, because the end result is always the same - the GSE's have their view and the DIY-ers have their own. All of the professionals who have posted on here are genuinely very helpful - and the principle of what is being said is completely on point. You get all manner of people trying to DIY and some may be more capable than others, so the caution is understandable.

    However, on this particular topic of a pressure reducing valve, I have to disagree. Heatrae Sadia's literature states that maintenance of the integral strainer should be performed by a "competent person". We can argue over what exactly that means, but I do not believe it equates to a G3 certified engineer. Indeed, I've seen plenty of Gas Safe registered engineers (who have NOT done the 1 day G3 course and do not hold the certification - I checked), servicing a pressure reducing valve, where the HW system happens to be an unvented cylinder - are they breaking the law? I don't think so, but happy to be corrected.

    As I said in my previous post - if OP had come on here and asked for advice on how to clean a strainer on a pressure reducing valve (with no mention of an unvented cylinder), then any question of being G3 qualified would not have come up.
     
    Last edited: 27 Mar 2021
  16. ianmcd

    ianmcd

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    you dont have to have any gas qualifaication of any description to be G3 qualified, you certainly dont have to be GSR

    you have to prove competency and one way of doing that is by holding the G3 qualification, there are others

    yes they are breaking the law if not competent
    only supplying the information that you want to supply will never get the correct answer, the correct answer in this case is get the unvented serviced as is required anually, by a competent person
     
  17. muggles

    muggles

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    Wow, that's quite an attitude you've got there. You're not going to get much help here if you start being rude to people.

    This thread is now locked. The professionals on here were correct about the need for an unvented cylinder to be serviced by a competent person and we would not advise it on a DIY basis.

    Muggles has not complained to the mods his was merely the last post before I saw and locked the thread.

    Moderator
     
    Last edited by a moderator: 27 Mar 2021
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