Had a calamity the other day when we found that we had a leak in our central heating system pipework. In the excitement (!) to dig up the tiled bathroom floor we MAY have managed to reverse the polarity of the two pipes concerned that feed from the boiler. Does it matter which way round the water flows through the system ? Is the there any simple way to discover if I have them the wrong way round ? Thanks
You should have an adjustable gate valve or TRV on rads usually fitted on the flow side with a locksheild on the return. Check which pipe gets hot from cold first at a rad. This will be the flow.
It matters if it flows the wrong way through the boiler! The boiler thermostat is near the outlet pipe. If this point becomes the inlet instead, the thermostat will sense the cooler return water instead of the just-heated water - and the boiler will overheat.
The flow and return pipes on the boiler should be labelled. If not, you'll have to refer to the installation manual. When correctly connected, the flow pipe will be considerably hotter than the return pipe.
Most TRV's for some years can be fitted on either end. I usually fit on the return side, where the pipework will be cooler and have less direct thermal effect on the TRV sensor. So in short, I don't believe you can use this method to tell which is flow and return.
3-port valves always go on the flow side AFAIK.Thanks guys - all useful stuff ! To be a little more specific about my problem the problem occurred with two 22mm plastic pipes that run up the wall in the hall. There was leak where they joined other pipework under the bathroom floor above. Whilst I took up the tiles in the bathroom to gain access, my wife chopped out the two plastic pipes all the way down to the under the hall connections with the idea that I would then replace the plastic with copper. However in the fun of the moment we didn't pay enough attention to which pipe from below the hall joined to which pipe above the hall ceiling (in the bathroom floor). I have completed all the pipework now, re-filled the system and am now running it up. Apart from a lot of airlocks it appears to be working OK but I am still concerned that I may have reversed those joints. The boiler (which is situated 30 yards from the plumbing incident ) is firing up alright and the correct outlet pipe (ie the flow) is getting hot first. Would this have happened if I had incorrectly joined the pipes ? Thanks again for all this valuable help.
They're unlikely to cross over in this sort of run so I'd guess it would be difficult to get them wrong.
It sounds as if you're probably ok.
The rest of the system probably doesn't care too much as long as the boiler is the right way round. The only exception to this is that some TRVs are noisy if the flow is in the wrong direction, and - for reasons which I don't understand - Honeywell say that their 3-port valves *must* be in the flow pipe.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.