Another invaluable piece of info, thanks for that. I was just re-watching an old video of yours regarding leaking stop taps and again a priceless titbit of info that's helped me out a few times. These sorts of videos that you and Robin do are a great source of information and are superb because of how short and straightforward they are. Many thanks again 👍

I had this exact issue in house I bought where the plumbing was converted to a pressurised hot water tank for a loft extension with an extra en-suite bathroom. In summer some of the downstairs radiators got warm from the lockshield ends. Four British Gas engineers tried to fix it over 3 days. They changed the motorised valve twice! They couldn't work it out and left it unfixed. I then got in local independent heating engineer out who diagnosed the problem and fixed it with a non return valve on the hot water return as you described in a mornings work. Great video, spot on.

Love these SB videos. Amazing knowledge and very clear when explaining how things work. I have this issue so know what to look for now. Thank you.

An excellent teacher, clear and precise and has a way of explaining in detail that is very helpful to many.

I think you may be a wizard! This has been bugging me for ages and this was such a simple and clearly detailed explanation that you’ve made it seem completely obvious.

As usual you have done great work and explained your own experience to be helpful for others. Many thanks Roger.

its always a joy to listen to someone who really knows his onions! Brilliant explanation

Roger job spot on, well explained. The time taken is worth it 👌.

Absolutely spot on & exactly what was happening to my system! I tried everything to find out why this was happening, and it wasn't until I got rid of my heat only boiler, and changed to a combi boiler. The connection from the HW return was connected to the radiator return pipe under the floor. This was done when the house was built! Lazy plumbing indeed. Thank you 👍

A decent explanation of a problem most plumbers/heating engineers have come across. Just moved house and it’s happening in mine too! 😀 Need to get round to draining it down and correcting before too much longer!

Hi Roger, Thanks for the clear explanation. I have that problem and never really found a clear explanation until I saw your video! Thanks

Well explained mate! Nice to refresh on these sort of things when you haven’t been jobbing for a while!

This is my favourite type of video, simple but really good. I think explaining stuff like this is your forte! (Not to say the other types aren’t good, but really like this format)

Hello Roger you are a great tutor for me because you speak my kind of uncomplicated language. I think a lot of tradesmen didn't have uncomplicated speakers like you when they were learning so they do their learning at the expense of their customers for many years.

Excellent explanation! thank you

Thanks Roger, that was a great explanation! (I actually have that minor issue with the rad nearest to the hot water tank) Although you explained the “wrong-way flow” and the one way valve solution very well, I think sometimes it’s the convection of the heat that creeps along the pipes, as opposed to an actual flow, so the one way valve may not necessarily function to prevent that…thank you for sharing 🙏

Great lesson. Thank you

I had the exact same issue on the same set up but it was the valve that had failed in my case. Another well explained & informative explanation Roger.👍👍

Excellent Roger. Thanks. Well explained.

Thanks for a great explanation, Roger.

Another terrific video. Thanks. We have only a towel rail heated in the summer via the boiler and all rads are off but still get warm despite TRVs off. Rads upstairs and UFL down. As soon as it gets warm I shut the lock shield valve down and this sorts the problem. A new installation (including a low loss header (no idea what that adds)) but after watching this I'm getting them back in! Cheers

Great stuff Roger , fully explained 👍👍👍

I had this, after I bought a run-down beautiful post-war end terrace in Scotland. It had a turret and spiral staircase, I loved it. Troubles made me sell it after a few years or updating, but the hidden issue was whenever the hot water cylinder was put to use, there was this trend to heat only the lower radiators in the house, not upstairs. I usually believe that once something’s done, I treat it as 100% until I find otherwise, this is one of the three times this has NOT held up! The system had two valves, but once I sketched it out I realised it needed a third. It had been relying on either the house being cold a lot, so some heating downstairs might not be a bad thing (!), or the owners had not noticed, etc. I fitted the third valve, which stopped the back-channel movement of hot water from the cylinder heating circuit, from going at all into the radiators backwards. It drove me nuts, but the present owner benefits as all of a sudden it’s not just a nuisance but an expensive one. As you will understand, the effect mainly was on radiators BELOW the level of the ‘head’ from the hot water entering and leaving the cylinder, which was perched in a corner cupboard of the kitchen, above the fridge. So, a three-motorised-valve system, instead of two, and it was perfect. Quite weird for me. Take care all. PS - have a laugh on me…the cost of the house when I bought it in 2003? £35,000 . 2 bedrooms plus a perfectly serviceable loft bedroom, and in fact this is what scuppered my letting plans - the government introduced a bedroom tax, and suddenly nobody moved because they;d have their benefits and home rooms scrutinised at that point, and this extra room was not ‘legit’. The council man said kindly ‘I am going to forget the request for retrospective approval, and put it in the drawer with the others’. I don;t understand hints, it’s terrible! He meant, I might be asked to return it to how it was, whatever that really means. It can mean, they examine the cables to see what date is stamped on them, but that’s a whole planning and building regs world of pain, let’s not go further.

Thanks, Roger. Indeed very useful information. Continue to keep up the good work

Thanks, exactly the problem iv got! Top man.

Brilliant as usual, we have just had this happen tonight 1st time in 6 years. Turned off the rads on the control unit and let's see what happens tomorrow.

Very informative guide thanks 👍👌

Absolutely brilliant explanation, totally correct. As you've probably guessed we have a similar problem, though only a few rads get a bit warm on top. But even if the primary return went closest to the boiler a strong pump action could still make the rads reverse circulate couldn't it ? Thanks.

Excellent Roger👍

Thanks Roger, more content like this please!

Found this video very informative and useful.

Roger, that might just explain my current problem! I had my combi boiler changed to unvented system and had it relocated in a different part of my house - have some but not all rads getting hot when calling for hot water . Plumber does not now what to do he has changed the 3 way motorised valve so hopefully when I show him your Video it will solve said problem! Thanks I appreciate the time and effort you put into producing these great videos. Ian

Perfectly understandable. Thank you very much 😊😎🇩🇰

Very useful information. Do you have a video covering a constant low level hum from a SSE 330 boiler - even when the CH and HW are off (at night)? Thanks

EXCELLENT EXPLAINATION THANKYOU

Very helpful, thanks.

Great content, keep it coming

Its only been like that for 8 years! We thought we were going crazy or the controls kept losing connection. Our underfloor heating warms the tank and our immersion cooks the underfloor heating. The pipe work looks a little more complex, but I can see the returns are fighting in an equal T. Thanks

solid information yet again :)

Very clear explanation Roger. I had this problem but with a different outcome so I will share it to help others. Rads getting hot when the heating was off but hot water on. Checked the motorised valve, all working correctly, even changed it, still no solution. Used my laser thermometer to see that the three port valve wasn't sealing. The rubber ball in the valve had just deteriorated and was allow some bypass. Changed the three port and the problem was solved.

Brilliant! Thank you.

Excellent timing for me Roger, I'd planned to replace my 3-valve this week to solve this exact problem and now I'm wondering if the problem is as you described. thanks!

This is really good thank you!

Excellent video mate

Thank you 🙏

Brilliant Roger 👍🏼

I learn a lot from these videos. In fact, I learn a lot from all your videos. Cheers Roger 👍

Now I understand. Thanks for posting.

Great explanation, have this problem, rads get a little warm when just HW on, installed by a professional as well....!

Thank you for the really useful videos. I had reverse circulation on my downstairs radiators. This was resolved my fitting a non- return valve. However the issue now is that when i have both the Heating and Hot water on at the same time, the downstairs radiators are not warming up? Any ideas what it could be? Could it be there is too much resistance because of the non return valve?

Perfect explanation. Theres a reason for everything ... when someone like you can articulate that it makes the world a better place. Now time to find that out of place T, on the return from the cylinder. My heat is on in my home, and the thermostat is off. Im thinking to myself, WTF?! Def. subscribing

Roger. Been around construction all my life coming from a building/construction family. Decided on plumbing as my profession. If i'd of had you as a mentor I'd of taken half the time to learn the knowledge. Took me a few years to grasp this particular fault find after my apprenticeship! Amazing explanation.

Thanks Great video! our gravity fed Y system (with cyl) is a you have described, but has a small lock shield valve quarter to half turned on on the cyl pipe return to the boiler. The return pipe is in the correct place as you describe but I understand the addition of a lock shield valve also helps slow down the heating water in the cylinder coil so that the water in the coil is not going too fast as to "whizz" through the cyl and therefor heats the water as effectively as it can. I believe that the lock shield addition on the pipe return from the cyl also means the boiler should not receive back cyl coil water that is perhaps still too hot. NB. I'm Just in the process of tidying up the wiring centre (this is has been been a mess) with the larger Salus wiring centre ready for Hive to work on Home Kit. ( Grundfos UPS3 pump is set to Prop Pressure & working fine) Thanks again great video explanation.

I had this in a house in London. Radiators were hot when the boiler was switched off. Eventually I found the pipes going to the tenants house. The landlord had connected his radiators to his tenants house next door.

Nice one Dave 👍

Really interesting, thank you.

Excellent

Roger, may I ask a question please? I've built an extension that I would like to run the GCH from the house to. I may need a bigger boiler but that's another issue. My question is could I take the extension return directly into the boiler return, close to the boiler, and the hot feed for the extension from the house radiator circuit feed? Thank you and thanks for this video. Anthony

Have this same issue but only with my living room radiator. I’ll give this a go!

any chance you could do a film about under floor heating converting normal radiator heating system if indeed this is possible

I have just got the same problem, atleast I have got an idea 💡 what would be the problem. Now I know what is the solutions. Thank you for making knowledgeable video. Blessings

appreciate it I have the opposite my CH is coming on when I put on the HW only It is not reaching the temp I would expect of 60 to 65deg c but only 54 deg c and no more Preumably because the rads are taking its potential to I keep trying to fix this to no avail Mr Bisby may i ask one thing😊 my HW cylinder return is 22mm buthas been reduced to 15mm and I do not think its connected to the return There is a H piece 22mm twin pipe connected to CH side but one of the pipes has an offset 15mm to the 15 mm pipe that is where it connects Could you help me identify the 15mm pipe if its the boiler return or a CH return and how do I find the primary return

Thanks for another great video, I have this problem but I have a combi boiler. Any ideas?

Even with the rads all tee'd before the primary return is there still not the chance of the water working back some, or would there be some sort of back pressure preventing it. Would it be reasonable to put a one-way valve in too, above the tee, but before the tank return?

Hi this has just started with mine. I have a combi boiler with a mega flow system and I have switched off the heating but have kept the hot water on a schedule. Now when the hot water comes on the heating comes on as well. The heating comes on at full blast. Does this mean my motorised valve need replacing?

Hi Roger, we have a baxi 428 combi and the central heating flow pipe gets very hot when the hot water is on even though the heating is off. Should this happening? If not, what would be the cause please? I did have a baxi engineer out as I felt the hot water wasn’t as hot as it used to be but he just said the weather is colder and dismissed my concern over the CH pipe getting hot. Any advice would be appreciated. Thanks

Brilliant video

Thanks

I'm going to start a campaign, to get you back on LBC radio " helps at hand phone in". Your brilliant and always liked listening to LBC when your radio show was on . Do you also remember the name of a motoring expert that was on LBC at roughly same time as your show? I think his first name was Gerrard?.

Great piece of advice Roger! Appreciated. Cheers.

Bravo! Another nice video. Honest & true. Thanks. Yes now that you have reminded me I have heard about this reverse flow phenomenon. There's another similar possibility isn't there? To do with the header tank feed thermo-siphoning. So you feed it in BELOW the return from a sort of U bend so that the heated water cannot rise. Anyway my heating has worked fine for 17 years but this Summer the rads are getting slightly warm when there is a HW demand, I thought it must be the valve. But is it the ball or the motor? Should I bite the bullet and replace both bits of it? Can the ball be fixed in any way? Why would it get stuck or not seat?

I have two 2 way motorised valves, both brand new, when i want just hot water, they radiators heat up, any ideas, both valves are working ok.

Hi, great video; would this problem occur If an extra radiator has been installed and that one is the only rad getting partially warm when the hot water is regenerating? Kind regards

I have this problem really great to understand why! My DIY solution - the radiator closest to the cylinder I switch off in summer seems to stop the reverse flow.

Rog knows his stuff! 👍🏻🙂

October now. New boiler fitted in 3 floor house by Brit Gas last month. When heating goes off, top floor rads v hot. Same floor as emersion tank. Initially top floor rad long to heat. Now the opposite. Rads had power wash. Something stuck? What's the problem, do you think? Advice appreciated!

Hi roger Great channel and video If i just have one radiator getting hot on the first floor when boiler on the ground floor how do i solve the issue ? Will i still need to lift boards to access pipework ?

Hi Roger, great channel. Only thing I do different is run the heating to define flow and returns after I've witnessed the problem with just the hot water on. If the same pipe gets hotter it's the valve leaking, if the other one does it's reverse circulation.

Thanks for that. I've been going crazy for the past week trying to understand what is going on with this three-way valve and Honeywell actuator on my heating system.

Great video, Im an amatuer but I thought the pump in the airing cupboard pumped it one way? so i don't understand!!...Also, does the 3 port valve let the hot through to the radiators when the flow is reversed, hence the heating on when I don't want it. I'm not sure which way my flow was at the radiators so i can't test by feel. i've replaced the 3 port valve motor following your tutorial and the problem came back after a while so i replaced the pcb and still got the problem.....could it be the internals of the valve body itself sticking open? would appreciate any help.

Very good content

What about bypassed towel radiators? Have come across this when towel radiator heats both on Hot Water and Central Heating. Is that still an acceptable installation technique?

nice video, thx :)

Great advice, as an amateur I would have thought just of the 3 way valve. However what I would say is that if this problem suddenly occurs some time after installation, I would think it unlikely the install problem that you describe as it would have been like it from the start....No?

Good one Roger 👍🏼 My shower mixer doesn’t go completely cold on the coldest setting. Is that likely to be design or installation error?

Your're a master 👍

Brilliant. Makes sense to me :)

well done

Hi Rodger Great informative video as always. I also have this issue but with my combi boiler which was only installed a year ago is there any different issues with this or is it a case where as you mentioned they have joined the return in a similar place ? Thanks

FANTASTIC nice and simple I also had a run in with British Gas 6 engineers came round still could fix my problem they couldn’t run a bath shame the is not enough good plumber like yourself. Great videos 👍👍👍👍

Many thanks . will look for that now, Bloody hate it when rads get hot when not needed. rgds Don

Nice vid. Be even better if you did a loft opening enlargeing video lol. Keep em coming

Thanks roger, you’re such a generous man....👍

Many thanks for explaning this problem,as I have a recurring problem with my central heating that I can not sort, Hopfully I will come across it in one of you blogs,

I have had problems with my entrance heating. I have had 3 new 3 valve changed. I think it is now, after looking at our youtube I think it is revers circulation problem? My question is could you just change around the valves on the radiators? I had a new boiler and tank fitted 2 years ago. Can you give me some advise?

Hi Roger, thanks so much. Our radiators do this but they get absolutely boiling hot in the summer not just warm, would it be the same issue ? It’s a new renovation so all pipework is new. I’ve had the plumber look at it but he couldn’t find anything wrong. Split system our underfloor heating downstairs is fine but all radiators on the 2nd thermostat system do it.

very good

Excellent diagram and explanation of what can or might be problems. Thanks Rodger a little bit of knowledge is better than none👍👍👍

Great video I have this exact issue but only 1 radiator getting hot in the hallway instead of all of them…..could it still be this issue that you have explained?

Excellent video. One question I have is that we have a loft conversion and the radiator in the bedroom in the loft conversion gets hot when the hot water turns on, but no other radiators do in the house (they get hot when heating is on). Is it possible that this problem can effect just one radiator?