Blockage in supply pipe from boiler to cylinder

[Morris134]

Hi:
I have an unvented system and there's a blockage somewhere in the supply pipe from the boiler to the water cylinder. I say this because the central heating and all radiators are working fine. The zone valve has been checked and is ok and I can get hot water fine switching on the immersion heater.

It's been recommended by SSE/Hydro that I need a power flush but separately by a plumber that a chemical flush would do the trick. So, I'm confused. Would a power flush be necessary, but would a chemical flush work? (By the way, the system did undergo a power flush around 5 years ago). Advice much appreciated.

 

[erj]

this is a fully pump system so a blockage on a 22mm pipe unlikely. Is there a air vent at the cylinder end on the flow pie? if so check it is not full of air.

 

[Morris134]

Thanks for your advice. I've unscrewed the air vent a fraction but there's no air trapped - just water there. Regarding your remark about 22mm pipes, those who installed the system unfortunately did so on the cheap and used only 15mm pipes :-(. I should have mentioned that before.

 

[Morris134]

Thanks for your advice. I've unscrewed the air vent a fraction but there's no air trapped - just water there. Regarding your remark about 22mm pipes, those who installed the system unfortunately did so on the cheap and used only 15mm pipes :-(. I should have mentioned that before.

Two pics of cylinder arrangement:

 

[erj]

what happens if you open the zone valve by hand or take it off altogether and turn the shaft with a pair of grips?

The photos are a big help.

 

[Reg Man]

what happens if you open the zone valve by hand or take it off altogether and turn the shaft with a pair of grips?

The photos are a big help.

What ever you do don't leave the head off, this is linked to your overheat stat i thinks.

 

[erj]

just checked the photos again can I see a gate valve on the return from the cylinder?, if so try opening it up just in case some muck has stuck there.

 

[Morris134]

just checked the photos again can I see a gate valve on the return from the cylinder?, if so try opening it up just in case some muck has stuck there.

Hi:

I've taken the zone valve off and operated the shaft by hand. No difference. The pipe below anyway remains cold.

Gate valve - please see photograph. Is this the gate valve?

 

[erj]

thats the gate valve, just turn it with a pair of grips and see if any thing happens, if nothing Iam stuck.

 

[Morris134]

thats the gate valve, just turn it with a pair of grips and see if any thing happens, if nothing Iam stuck.

I've tried but ...nothing. Anyway, many thanks for your help.