No Hot Water - Gravity Fed System

[Monkey Wrench]

Ok, so I went back last Monday and, before checking pipework with a magnet, turned the hot water and heating on. As previously stated, the hot water cylinder is in the loft and the flow/return pipe run from the Rayburn in the kitchen to the cylinder in the loft (via pump & diverter valves under first floor hall) is about 30-35 feet. After turning the hot water/heating on, I went straight up to the loft to check the cylinder (took a couple of minutes at most) and the flow pipe to the cylinder was already getting warm and after another minute was hot. However, after a few further minutes, the return pipe hadn't warmed up at all.

I then part drained the system, disconnected the flow/return from the cylinder and ran some water through the cylinder (not mains pressure but using a bottle of water) and, apart from a bit of discoloured water coming out the other end, found the cylinder coil to be clear.

I've checked 50% of the flow/return pipework to the cylinder with a magnet (the other 50% is in a difficult to access loft/ceiling void) and it's clear.

Surely, if there was a blockage, there's no way the flow pipe at the cylnder would have warmed up so quickly (if at all) as there's no where for the water to go !

 

[Best]

Ok, so I went back last Monday and, before checking pipework with a magnet, turned the hot water and heating on. As previously stated, the hot water cylinder is in the loft and the flow/return pipe run from the Rayburn in the kitchen to the cylinder in the loft (via pump & diverter valves under first floor hall) is about 30-35 feet. After turning the hot water/heating on, I went straight up to the loft to check the cylinder (took a couple of minutes at most) and the flow pipe to the cylinder was already getting warm and after another minute was hot. However, after a few further minutes, the return pipe hadn't warmed up at all.

I then part drained the system, disconnected the flow/return from the cylinder and ran some water through the cylinder (not mains pressure but using a bottle of water) and, apart from a bit of discoloured water coming out the other end, found the cylinder coil to be clear.

I've checked 50% of the flow/return pipework to the cylinder with a magnet (the other 50% is in a difficult to access loft/ceiling void) and it's clear.

Surely, if there was a blockage, there's no way the flow pipe at the cylnder would have warmed up so quickly (if at all) as there's no where for the water to go !

Yes, the flow pipe can heat up fairly quickly as it is only the water in the pipe heating up. It may only be passing through it very little due to a blockage or air lock. I see this very often on a cylinder with return pipe nearly blocked totally. Something strong, but flexible pushed down into pipe would be handy.

 

[SimonG]

Airlock.

 

[kris]

Ok, so I went back last Monday and, before checking pipework with a magnet, turned the hot water and heating on. As previously stated, the hot water cylinder is in the loft and the flow/return pipe run from the Rayburn in the kitchen to the cylinder in the loft (via pump & diverter valves under first floor hall) is about 30-35 feet. After turning the hot water/heating on, I went straight up to the loft to check the cylinder (took a couple of minutes at most) and the flow pipe to the cylinder was already getting warm and after another minute was hot. However, after a few further minutes, the return pipe hadn't warmed up at all.

I then part drained the system, disconnected the flow/return from the cylinder and ran some water through the cylinder (not mains pressure but using a bottle of water) and, apart from a bit of discoloured water coming out the other end, found the cylinder coil to be clear.

I've checked 50% of the flow/return pipework to the cylinder with a magnet (the other 50% is in a difficult to access loft/ceiling void) and it's clear.

Surely, if there was a blockage, there's no way the flow pipe at the cylnder would have warmed up so quickly (if at all) as there's no where for the water to go !

When u emptied the system did u manually open the zone valves to allow proper filling of the system , ?

 

[Monkey Wrench]

Thanks again for the responses.

Yes, the flow pipe can heat up fairly quickly as it is only the water in the pipe heating up. It may only be passing through it very little due to a blockage or air lock. I see this very often on a cylinder with return pipe nearly blocked totally. Something strong, but flexible pushed down into pipe would be handy.

Ok thank you, certainly worth a try with a sturdy piece of flexible hose pipe.

Airlock.

Thank you, but I've loosened both the flow and return connections at the cylinder and there's water at both. There's also an auto air vent on the cylinder flow pipe so surely any airlock would have vented out through that by now !

When u emptied the system did u manually open the zone valves to allow proper filling of the system , ?

Thank you, yes, I manually opened both zone valves.

 

[Best]

You can still have an airlock. Pipes will fill up with water but still leave air trapped somewhere on a level pipe or high spot. Might be best to try a careful blast of mains water through them if all else fails.

 

[Monkey Wrench]

You can still have an airlock. Pipes will fill up with water but still leave air trapped somewhere on a level pipe or high spot. Might be best to try a careful blast of mains water through them if all else fails.

Thank you, yes, definitely worth a try before I start trying to push something down the pipe. Where do you think the best place to connect the mains feed would be, in the loft near the cylinder ? If so, I'll have to do a partial drain in order to fit a tee and and an isolationg valve.

I guess I'd obviously have to open the drain valve at the same time as blasting the mains water through otherwise the F&E tanks going to fill up rather quickly !

Thanks again.

 

[lucas121]

We recently worked on a plastic sealed system that must have been poorly installed as there were air locks everywhere, even when it was fed by mains pressure.

In the end we had to connect the power flushing machine, cleared the air locks in seconds.

 

[Monkey Wrench]

We recently worked on a plastic sealed system that must have been poorly installed as there were air locks everywhere, even when it was fed by mains pressure.

In the end we had to connect the power flushing machine, cleared the air locks in seconds.

Thanks for that but unfortunately I don't have access to a power flushing machine. I guess I could always try and use a powerful wetvac but I haven't a clue how I'd connect the nozzle to the drain off !

 

[Coldfeed]

It was hard for me to get what your saying. So are you saying you changed the motorised valve for the hot water/ so the coil one yet your not getting hot water out the cylinder but you've got hot water to the valve

 

[jam1979]

Has the cylinder got water in it by that I mean have you checked the ball valve for sticking

 

[Monkey Wrench]

It was hard for me to get what your saying. So are you saying you changed the motorised valve for the hot water/ so the coil one yet your not getting hot water out the cylinder but you've got hot water to the valve

I had to part drain down the system in order to change the hot water zone valve body only (not actuator head). On refilling the system, I could not get the hot water circuit back again due to either an airlock or blockage. Despite several attempts to rectify it, the hot circuit is still not working !

 

[Monkey Wrench]

Has the cylinder got water in it by that I mean have you checked the ball valve for sticking

Yes, the cylinder is definitely full of water.

 

[Coldfeed]

I had to part drain down the system in order to change the hot water zone valve body only (not actuator head). On refilling the system, I could not get the hot water circuit back again due to either an airlock or blockage. Despite several attempts to rectify it, the hot circuit is still not working !

So only cold water out of the hot tap? And is there hot water on the flow to the coil up to the motorised valve? If so have you tried manually opening the valve

 

[Monkey Wrench]

Just to update, I received a text from the customer last Thursday morning to advise that they now had hot water and everything was working ok so it seems the "airlock" finally shifted to the loft and out of the vent.

Thank you for all the helpful advice.