I could use a quick bit of advice if possible please. I will explain the situation in as few words as I can listing just the important stuff. I would like to know if running the system as it is could cause any damage to anything, or reduce it's life? I had a new 18/25 Utility System boiler fitted, My system is S Plan and before the new boiler it wasn't sealed, now it is and has an expansion vessel. Boiler fitted over 2 days - When fired up downstairs rads got hot, upstairs didn't - Stone Cold. Hot water working OK. 2 Day wait for engineer to come back - Diagnoses the problem to a faulty non-return valve stopping the water flowing upstairs. He didn't touch that pipework so the fix will be chargeable and treated as a new job. Can't do it there and then as wants to go home. 10 days later he comes back - Removes non return-valve, adjusts pipework slightly and upstairs starts working fine right away. Next day - I'm tidying up and notice that the arrows on both my zone valves (HW & Rads) are pointing the wrong way so I send an email to engineer with a picture saying "My zone valves are the wrong way around" Reply by email points out that he didn't touch them and the fact that everything is working means they are okay as they are. My reply was along the lines of "the zone valves don't have arrows on them for fun and I want the system right", I also pointed out that if he had noticed this when the system was drained down, and half the pipework was cut away, it would have been a 15 minute job to swap them around, but now it's all back up and running it will be considerably more work, and also that I would have expected him to spot it, especially as the valves are both right in the area in which he was working. Reply by email says that he wasn't looking for things like that and would have expected them to be right, and if he had noticed he wouldn't have had time to put it right anyway as he worked late enough as it was. In my reply to that I said I was going to check with the guy who installed the zone valves (10 years ago) just incase there was a good reason why they were reversed, and asked them (again) how long it would have taken to swap the valves around when system was drained and pipework cut away, and how much they would charge me to come out and do the job. I have had no reply to that email. After spending hours looking at pictures, making phone calls and looking at installation instructions I have worked out that the zone valves were originally fitted on the return, now they are on the flow.. so it's been plumbed in the wrong way around and the water is being pumped around the whole system the wrong way. That explains why the upstairs didn't work to start with, the non-return valve that I paid to have removed wasn't faulty at all and didn't need to be removed. I haven't spoken to the engineer yet, I'm writing a fairly long email to him at the moment and will send it in the new year on Monday. I just want to know if I'm likely to damage anything running the system in reverse, and if the life of any of the components is likely to be shortened because of this? Any other comments or observations about this situation are welcome!