This is a follow-up question to https://www.mybuilder.com/questions/v/52403/pressure-increasing-on-pressure-relief-valve as I now have more information.
I have a Heatrae Sadia Megaflo unvented system. The water pressure in my flat has decreased over the years and so a plumber replaced what I now know to be the Cold Water Combination Valve (including an attached expansion relief valve connected to a tundish and discharge pipe) with a Pressure Reducing Valve. The PRV isn't connected to a tundish/discharge pipe. The water pressure is now brilliant again however I noticed that when the boiler is heating the hot water (not the central heating), the gauge on the PRV increases a lot. We have turned down the pressure on the PRV but this isn't a proper fix as surely, the pressure shouldn't increase at all? This feels like a sticking plaster rather than a fix.
I have a few questions:
1) Is it appropriate to replace a Cold Water Combination Valve with a Pressure Reducing Valve?
2) Is the behaviour of pressure increasing when the boiler is running to be expected given the replaced part?
3) Do I need to get the PRV taken out and replaced with a new Cold Water Combination Valve?
Thanks for any advice - I appreciate it!
Are you a tradesperson and able to answer this question?
If your water pressure and flow rate was resolved then the combination valve may have been the answer. If you are experiencing any problems with an increase of water pressure
if you still aren't satisfied, my personal level would be to call in a qualified G3 technician, as these systems have their tiers of safety that aren't supposed to be adjusted tampered with.
Hope this helps
Thanks pd
NO a PRV is never to be put in place of a cold water combination valve. The combination valve has safety devices fitted I.e an expansion relief valve.
My advice to you would be to turn off the supply to your cylinder, and have a qualified unvented plumber replace the PRV with the correct cold water combination valve.
Where do you live? If your close I am more than happy to come and have a look for for you. I am fully unvented qualified and deal with these kind of cylinders on a daily basis.
If you would like to contact me please feel free to do so on 07757796010.
Answered11 July 2019
0
Anonymous user
The combination valve is more than just a prv, and when used in conjunction with an unvented cylinder should always have an expansion vessel and discharge safely onto a tundish and be piped to a safe discharge point as stated in building regulations. To replace the combination valve with a normal prv is illegal and dangerous. You should turn of the water supply to the cylinder and open a hot water tap to relieve the pressure. Then find a qualified unvented cylinder engineer, who should have a G3 certificate to work on these systems.
sounds very much that wrong valve as bee fitted, was you plumber registered to work on unvented systems?, what make of valve as been fitted, if any doubt you should contact heatrae and ask for one of there installers in your area
