presure redution valve fitted with a temperature control valve

[kieronriley]

hi we have just fitted a pressure reduction valve to reduce cold mains pressure going into a temperature control valve ( this is in children's nursery to ensure hot water wont burn kids hands) the hot water is from a vented tank, now can the cold water push the hot water back up to the cylinder through the pressure valve .the hot water side of the temp. valve goes cold as soon a you turn off the hot tap and If I turn the pressure valve down any more the flow from the tap which is not that god anyway drops to much,any advice please .thanks. Kieron

 

[chris watkins]

hi we have just fitted a pressure reduction valve to reduce cold mains pressure going into a temperature control valve ( this is in children's nursery to ensure hot water wont burn kids hands) the hot water is from a vented tank, now can the cold water push the hot water back up to the cylinder through the pressure valve .the hot water side of the temp. valve goes cold as soon a you turn off the hot tap and If I turn the pressure valve down any more the flow from the tap which is not that god anyway drops to much,any advice please .thanks. Kieron

Yes, get a plumber in who has their Water Reg's & Part G tickets. They will be able to advise you on whether what you have installed will ever work and meets the requirements of the Water Regulations 1999 / Building Reg's of course they will probable want to charge you for the advice given &/or work carried out.

I am afraid you have found out that not all plumbing jobs can be DIY'ed.

 

[kieronriley]

Thanks for you reply, as a trainee I was trying to impress my boss with my problem solving abilities,I have been trying for nearly two years to get him to use a computer more often to research things and this time I definitely failed and it just gave him a good laugh and another reason not to use the computer.he has now fixed it as he said without that bloody gismo but with learnt knowledge,and has left me to discover how if I can with that bloody gismo,so thanks again.Kieron

 

[Dotty]

Kieron

If you had included that in your opening post we would have tried harder to help you, however, as you now know there are rules and regulations applying to unvented systems which mean we try and take a responsible attitude towards giving advice. Especially as there would undoubtedly be the have a go hero looking to repair his own system.

One of us would probably have given you a spot more advice via pm to help you impress your luddite boss!

 

[DrainMedic]

For future reference Kieron, most Thermostatic Mixing Valves now incorporate non return valves on both Hot and Cold inlets. It's always worth checking though, and where they're not fitted, it's a good idea to install one on the hot side, to prevent high pressure cold water, as you say, from pushing the low pressure hot back up into the cylinder.
Ofsted insist on TMVs being installed on all sinks and basins that children have access too. Also, it's a requirement for them to be installed to disabled systems too.
I can understand people not wanting to offer advice for certain plumbing jobs, but as your system is not a pressurised system (you say it's vented) then I can't see the problem personally? If it were unvented, then it'd be different, but then again, you would have the problem, as the pressure would be fairly equal on both sides of the TMV.

 

[kieronriley]

Thanks very much for your help. Kieron

 

[chris watkins]

For future reference Kieron, most Thermostatic Mixing Valves now incorporate non return valves on both Hot and Cold inlets. It's always worth checking though, and where they're not fitted, it's a good idea to install one on the hot side, to prevent high pressure cold water, as you say, from pushing the low pressure hot back up into the cylinder.
Ofsted insist on TMVs being installed on all sinks and basins that children have access too. Also, it's a requirement for them to be installed to disabled systems too.
I can understand people not wanting to offer advice for certain plumbing jobs, but as your system is not a pressurised system (you say it's vented) then I can't see the problem personally? If it were unvented, then it'd be different, but then again, you would have the problem, as the pressure would be fairly equal on both sides of the TMV.

Just so Kieron (& any others) don't get confused Mr Medic -
Under the Water Regs when Hot (cat 2) mixes with Cold (cat 1) in any valve, there is a requirement to provide suitable back flow protection to both supplies Hot & Cold.
You are correct that a lot of shower & blending valves do now come with them installed but not all cases, so as plumbers we need to check, if they are not in place then we must provide them, normally single check valves on each.

Unless things have changed recently I believe it is not a requirement to install a blending valve to a disabled WHB, but it of course would be good practise. Thinking back to the cheaper Doc M packs the basins they only came with a mixer tap which was set to limit the blend of cold to hot so not strictly a TMV 2.

 

[DrainMedic]

Just so Kieron (& any others) don't get confused Mr Medic -
Under the Water Regs when Hot (cat 2) mixes with Cold (cat 1) in any valve, there is a requirement to provide suitable back flow protection to both supplies Hot & Cold.
You are correct that a lot of shower & blending valves do now come with them installed but not all cases, so as plumbers we need to check, if they are not in place then we must provide them, normally single check valves on each.

Unless things have changed recently I believe it is not a requirement to install a blending valve to a disabled WHB, but it of course would be good practise. Thinking back to the cheaper Doc M packs the basins they only came with a mixer tap which was set to limit the blend of cold to hot so not strictly a TMV 2.

've just re-read my post and its a bit misleading! I was trying to get across to Kieron the reason why we install a NRVs on the hot side. I suppose I should've stated that one should be installed on the cold side too, along with the reason why.
The mention of it being a requirement to install TMVs in disabled WHBs referred to it being a requirement of OFSTED rather than an 'across the board' requirement. They seem to have rules for themselves which seem ridiculous sometimes. One example being the height of pipework; I recently had to move a pair of pipes up above 1800mm, I assume to keep them out of the reach of the kids. I asked the question if they could be boxed in instead and 'no' was the response from the really helpful OFSTED inspector. A different inspector returned a week later to carry out another inspection of the 'snagged' works - which included decorating, bacterial swabs, plumbing, joinery etc - and when I asked her why the pipes couldn't have been boxed in instead of moved, she said they could've stayed where they were without any boxing in either!

My post was aimed at Kieron's specific circumstances - apologies for any confusion!

 

[chris watkins]

It would seem that OFSTED should stick to their original remit which was education.

Having 1st hand experience of (ex) teachers trying to run an organisation, I would be very weary of letting them loose in a education establishment looking at teaching standards, let along building trades installations.