OSO Indirect 250 Unvented Tundish Dripping

[chalky71]

Last week I noticed that the tundish was dripping and followed the normal procedure:

Cold or tepid water discharge from tundish
1. Turn off the electrical supply to the immersion heaters.
2. Turn off cold water supply valve.
3. Open a hot tap.
4. Drain water from commissioning valve (12) until water flow stops.
5. Turn the knob on the Temperature and Pressure Relief Valve (5) to the left and hold in this
position until water flow stops from the commissioning valve.
6. Close commissioning valve.
7. Close all hot taps.
8. Open cold water supply valve.
9. Turn on electrical supply to the immersion heaters.

However, when on number 4 above, there was no water! It now seems to be getting worse so is there another way to stop it. For example can I just leave the hot water tap on downstairs, would it do the same job? I've attached some photos.

Thanks in advance. I normally just call out British Gas but they won't come due to Coronavirus.

 

[picasso]

Why are you using the immersion heaters ? the gas boiler should be doing the work, the small rubber washer in the draincock/commissioning valve is probably stuck on its seating.

 

[chalky71]

I don't believe that I am using the immersion heater, any reason why you think I am?

 

[picasso]

Number 9 "Turn on electrical supply to the immersion heaters."

 

[chalky71]

That's just a safety procedure, i.e. isolate it before doing any work, I'm not actually using it

 

[Madrab]

If you turn on the electricity to the immersion heaters, then they're usually turned on . i.e. they would normally warm up and be creating hot water.

That being said what version of OSO is it, can you give us the version/model number?

As @picasso mentions, the commissioning (drain) valve washer is probably stuck. With a hose tight onto that valve run into a bucket, open up the water supply to the cylinder and open that valve slowly, the mains pressure should hopefully shift the washer off it's seat.

 

[chalky71]

Thanks regarding the note about Immersion Heater, it's definately off.

It's an OSO Indirect 250. I did what you said with the commissioning valve and water flowed out. I then closed the cold water feed and opened the Pressure Relief Valve as per the procedure and hot water flowed out from it down into the tundish pipe outside. The commissioning valve then reduced to a trickle. After a while the hot water stopped and I could hear gurgling from inside. So closed commissioning valve and switched cold water supply back on and same problem, cold water continue to drop from tundish

 

[Madrab]

Can you give us a close up picture of the whole of top label where is says "notice to"

It's either a Pressure Relief Valve or an expansion issue by the sounds of it.

 

[chalky71]

Also spoke with OSO (very helpful) and they said the same thing. It's replacement part number 355045. Thanks for your help.

 

[Madrab]

I wouldn't go running to get one yet, you need to know what the issue is first. If it's not holding the bubble (if that unvented cylinder has an internal one, hence the need for the model number, pic of that top label) then that's one issue, if it's the PRV itself passing then that needs replaced.

You need it serviced by a qualified engineer, you cant DIY repair these cylinders.

 

[chalky71]

Absoluely, got a service contract with British Gas so will just have to wait until they can come out to do it. I'll attach the label pic in a minute.

 

[chalky71]

Finally got a qualified plumber out to look at this and changing the inlet control valve (https://www.unventedcomponentseurope.com/oso-multibloc-inlet-control-valve-22mm-355045.html) fixed the issue I live in a hard water area and it was last changed five years ago.