S
Synec
Excessive pressure drop in Megaflo UV Mark 1 2002
My first posting on this website and I apologise for it being a long one:
A domestic hot water set up first installed in June 2002. It has given us nothing but headaches for 10 out of the last 12 years. At first it was the usual thing – constant dripping from overflow – along with a leaking tundish. Then the immersion heater coil failed after the second night of use. A lot of problems were apparently caused by excessive mains water pressure – particularly bad when over 10 bar but it has settled down to about 8-8.5 bar now. Don’t take my word for it, the measurements come from Essex Water – taken at the garden tap.
Anyway, we contacted a recommended and diligent plumber (UV/G3 ticketed with plenty of Heatrae Sadia experience) who renewed and rectified the slightly non-standard aspects of the original installation – but these seemed not to be major issues. The following were replaced:
In addition, he did some cleaning out of the cylinder via the heater port.
He also provided some enhancements that he thought might assist in future fault finding/ solving, these included:
In addition the whole house (except the MCW to the kitchen sink) is supplied via an Altecnic 535 22mm static/ dynamic pressure regulating valve set at 3 bar to help balance the supplies to bathroom fittings (basin mixer, shower mixer and bath mixer with handspray) and DHW to the kitchen sink.
Everything has worked very well without fault (18 months) until recently when we have noted poor or variable hot water pressure on all fittings.
I have partially dismantled, cleaned and refitted the Altecnic PRV and the Megaflo 3 bar PRV cartridges and reformed the bubble in the Megaflo. A slight improvement has been noted but essentially the same problem remains; water pressure is good to start with for about a minute or so until it tails off into a dribble from the shower head or bath tap. It also pulses slightly.
When all fittings are closed the incoming MCW pressure is noted at 2.8 bar, as is the HW pressure at the top of the cylinder. When a fitting is opened the incoming MCW pressure stays rock steady at 2.8 bar. The HW pressure slowly drops to less than ¼ of a bar and both flow and pressure reduces at any fitting that is open – including the kitchen sink downstairs. When it is closed again the HW outlet pressure rises very slowly back to 2.8 bar – takes about 3-4 minutes.
I will try to contact the plumber who carried out the work in 2012, but before I bother him (he was close to retirement then) I’d like to see if anyone on the forum has had similar problems and resolved them straightforwardly. Logic suggests the 3 bar PRV cartridge is at fault but it is less than 2 years old and does not see hard service as the upstream pressure is regulated to suit.
Given that it is an unvented installation I am limited in what I can do with it as a householder (I have probably gone further than I should with the 3 bar PRV) so am keen for advice on which direction to head next.
My first posting on this website and I apologise for it being a long one:
A domestic hot water set up first installed in June 2002. It has given us nothing but headaches for 10 out of the last 12 years. At first it was the usual thing – constant dripping from overflow – along with a leaking tundish. Then the immersion heater coil failed after the second night of use. A lot of problems were apparently caused by excessive mains water pressure – particularly bad when over 10 bar but it has settled down to about 8-8.5 bar now. Don’t take my word for it, the measurements come from Essex Water – taken at the garden tap.
Anyway, we contacted a recommended and diligent plumber (UV/G3 ticketed with plenty of Heatrae Sadia experience) who renewed and rectified the slightly non-standard aspects of the original installation – but these seemed not to be major issues. The following were replaced:
- Coldwater combination valve
- 3 Bar PRV cartridge and housing
- CW pressure relief valve
- HW temperature and pressure relief valve
- Immersion heater coil
In addition, he did some cleaning out of the cylinder via the heater port.
He also provided some enhancements that he thought might assist in future fault finding/ solving, these included:
- Twin tundishes, one from CW PRV and the other from T&PRV – commoned at low level into a single 22mm to waste.
- Twin pressure gauges, one to MCW inlet to Megaflo after the Combination Cold water valve and 3 bar PRV
- A capped off branch teed from the MCW via an isolating valve to allow later installation of an external pressure vessel in case the Megaflo bubble system ceased to work reliably.
In addition the whole house (except the MCW to the kitchen sink) is supplied via an Altecnic 535 22mm static/ dynamic pressure regulating valve set at 3 bar to help balance the supplies to bathroom fittings (basin mixer, shower mixer and bath mixer with handspray) and DHW to the kitchen sink.
Everything has worked very well without fault (18 months) until recently when we have noted poor or variable hot water pressure on all fittings.
I have partially dismantled, cleaned and refitted the Altecnic PRV and the Megaflo 3 bar PRV cartridges and reformed the bubble in the Megaflo. A slight improvement has been noted but essentially the same problem remains; water pressure is good to start with for about a minute or so until it tails off into a dribble from the shower head or bath tap. It also pulses slightly.
When all fittings are closed the incoming MCW pressure is noted at 2.8 bar, as is the HW pressure at the top of the cylinder. When a fitting is opened the incoming MCW pressure stays rock steady at 2.8 bar. The HW pressure slowly drops to less than ¼ of a bar and both flow and pressure reduces at any fitting that is open – including the kitchen sink downstairs. When it is closed again the HW outlet pressure rises very slowly back to 2.8 bar – takes about 3-4 minutes.
I will try to contact the plumber who carried out the work in 2012, but before I bother him (he was close to retirement then) I’d like to see if anyone on the forum has had similar problems and resolved them straightforwardly. Logic suggests the 3 bar PRV cartridge is at fault but it is less than 2 years old and does not see hard service as the upstream pressure is regulated to suit.
Given that it is an unvented installation I am limited in what I can do with it as a householder (I have probably gone further than I should with the 3 bar PRV) so am keen for advice on which direction to head next.
