Morning all,
I did as suggested. Bypass valve mostly closed, ensured some flow while tank was cold.Flow valve was half closed. This morning we didn't have any hot water so I've opened up the flow valve all the way to see if this fixes the issue.
At the moment I think that the pump may need replacing. We've not had any heat in the downstairs radiators and the pump is a little noisy. However, I've had mixed results when closing off all the rads upstairs which has resulted in some heat coming downstairs. System has been drained so sludge is not a problem.
My question as follows: If pump is on its way out and we have hot water/heat upstairs anyway , why would mostly closing the manual bypass cause a loss of hot water in the tank?