you have gravity hot water so there are no motorized valves.
The pipes fromm the boiler are 2*28 and 2*22.
It's not normal, but certainly not heard off, for gavity sysytems to block up, it's more likely to be an air lock, is the cylinder directly above the boiler or are they off-set?
If you need to find a tradesperson to get your job done, please try our local search below,
or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local