Poor pressure with oso unvented hot water system

[roberthgn]

I have an oso unvented water system. The idea was to enable constant pressure at all taps or showers (we have two showers). At the moment there is a discharge of water regularly from the tundish. When we flush the toilet the water pressure virtually vanishes at the taps until the toilet tank has filled. It is not possible to use both showers at the same time.

A plumber (not the original installer) has looked at the system and has said it needed recommisioning which he did. Things were ok for a few months and then the above problems have returned. The water supply to my house is only 15mm copper pipe but plumbers think this shouldn't be causing my problems especially the didcharge of water from the tundish. Any help would be appreciated.

 

[ChrisR]

You need to re-establish the air gap.
Same in principle as Megaflo (aka Megaflow)

Turn off CW supply.
Open lowest hot tap
Hold open the red (usually) topped (Pressure and temperature relief)valve on the side of the tank by turning it - you may get it to stay open, or you hold on for an eternity until the hot tap stops flowing. Could be 15 mins or so
(Let) close the red topped valve.
Shut hot tap.
Open mains supply.
Wait till filling noise stops.
Open that same hot tap - it will sputter a lot as the air comes out.
SHould then be OK for another 3 months - 2 years or so. Watch for continued drip at tundish. The valves can "let by".

 

[bab]

OSO & Mega flows same dog different country. Both require draining & refilling at least every 12 months to regenerate the air bubble at the top of the cylinder to accept the expansion of water.If the air has depleted into the water then the pressure will rise up to the safty discharge level then it will drip into the tundish & out side. thats the idea but a lot of the time the tundish dont catch it all & uget a wet floor .There is a step by step blue sticker on the side of the cylinder & in the M/instructions.on how to regenerate the air . Its not good to leave them in this sate. if all the saftey relief valves fail & the cylinder stat (slim chance but not impossible) these things explode like a bomb.A 15 mm supply is not the recomended supply it should be 25mm alk/ from the road then 22mm copper to the cylinder as a minimum. READ manufacture,s instruction's.Thats if u got good pressure if u aint its not that suitable.

 

[roberthgn]

Thanks to Chris R & bab for suggestions with my oso pressure problem. Will try this and see what happens.

 

[Cooperman123]

Can you get an unvented system where you don't have to refill every 12 months or so?