Brilliant and informative. Fitted a 3/4 bypass valve in a system with Trench Radiators just before the room Thermostat controlled TRV for them. If the room gets hot with its big floor to ceiling windows in the spring sunshine the boiler gets the hot water back and shuts off. Lots of solar gain and not wasted heating. Thankyou I fit kitchens and plumbers are so busy no one wants to fit my T/heaters. Thanks for your calm knowledge👌

Brilliant! Informative and very, very clear instructions. Much appreciated .

Your plumbing videos are the best on you tube. Hats off to you. You should run training courses.

Just to thank you. I have visitors coming in 2 weeks. Don't want them to be cold. Manged to get the all the radiators working , with yourhelp.

Thanks. I like the channel and very well explained. You can make this work by having a cheaper non modulating pump so that will keep the valve open when the modulating pump slows down if TRV's close or zone closes.

Like the way you also replaced that isolation valve on the discharge of the pump as those suckers tend to leak at the spindle and also seize in the open position....

Your video helped me out yesterday massively Thank you

Very good instuctional Utube - and I feel as though you are a friend, even though we have never met. Well done - you've saved me hundreds from getting cowboys in who never really seem to understand how the system works!

Very useful. Thanks for posting this.

Thanks for your help and advice. Great video 😊👍

Great video Dereton I remember the old bypass with the gate valve these are much better

Thank you for your video, apparently the new main boiler does not have a bypass built in it anymore so if all the thermostat valves are closed it will overhead. Your video has helped me. Thank you

This is why it is also good practice to fit atleast one without TRVs and fit lock shields. Preferably this should be nearest to the thermostat.

Another great vid from the master, thanks.

Another nice nugget of information.

thank you, very clear instruction.

Sorry Al, great video....

It's always sunny where you live, always rains right up in the north east

thanks for sharing

Also it avoids heat loss when open so its not circulating throughout the pipework it zones or TRV's are closed. Thats actually what it was designed for. Nice job on the video

thanks a lot for the clear instructions :)

Hey Al, have an issue with an automatic bypass valve that i think is causing the CH gas boiler to pump over... History as follows - - Home is 30 years old running an open vented F&E system. 9 Radiators. - Potterton Suprima 50l (2004) serviced and running very well. - Climote controller and 3 x Zone valves fitted approx 2 years ago. - Recently was in the attic and noticed quite bad condensation, noticed the vent pipe from the CH was pumping over into the F&E tank. Eventually figured out it was only pumping over when a single zone was turned on i.e upstairs heating only. - Had issues with cold spots on downstairs rads so ran X400 for nearly 4 weeks and drained the system, decided to remove all effected rads, cleaned and hosed them out thoroughly until they ran clear. 30 years of sludge was bad! Cleaned F&E tank spotless, refilled the system and added X100 inhibitor. I think that eliminates any chance of blockage/obstruction in the system as all rads heat perfect now with no cold spots. - The boiler is still pumping over on a single zone and as normal over-runs(but pumps over) for approx 2 mins when the CH is timed off. If two zones are put on together i.e upstairs and downstairs the boiler does not pump over except for when timing off… - An automatic bypass valves is fitted to the immersion pipes upstair in the cubby, I thought that may be the issue so tried resetting it by closing it fully to 0.6 and then turning off all the rads except one for the purpose of backing off the ABV until flow through… - Turned on the upstairs and downstairs heating and the vent pipe(blue) immediately got hot (system pumping over) the (green) pipe also got hot in the lower part but not in the upper part after the compression fitting and then the (orange) pipe got hot within about 3-4 mins with the ABV still fully closed, should that not be the case? Im confused as to the operation and location of the auto bypass valve, its there to prevent pump-over? is it working and fitted in the correct location, direction? Pics below of pipework above boiler and cubby for reference… ibb.co/JHyMb7z ibb.co/QYxzhfR ibb.co/3y4vc3x

Great video thank you so much

Thanks for the information.

Top video, thanks.

simple nice vid mate

Combi boilers usually have this built-in btw, have done for a long time.

cheers mate

thanks,well explained!

Awesome video

Thankyou for that insight very helpful. I have a similar system as yours Dereton33, just installed by British gas : my pump would hum when all the rad stats were closed I have had 2 British gas Engineers tell me I need to keep 1 rad open and use the wall stat in that room to turn off the heating : to stop the humming, "unbelievable" I did try it though just to say I tried it, my heating came on at 7am the wall stat turn the heating of at 9.15am, I was a bit nippy that morning.

Hi Al, I've got to replace my valve just wondered if you've ever froze the pipes rather than drain the system? Good or bad idea. Cheers

I'm guessing you'll struggle to use the chart with these modern Combi types that have variable pumps though? But, as you say, maybe adjust by feel. Good vid, thanks :)

Thanks for that - Our system seems to be using the secondary coil in the immersion copper cylinder in the immersion cupboard as a 'relief system' / bypass if all the radiator TRV's were closed - have you ever seen that kind of system? - I dare say you have. There is no zone valve to shut off the HW to the immersion tank coil so i have to make sure the oil boiler stat shuts off at between 60c-65c which is a bit of a pain because if i wanted say 70c in the rads but 60c in the immersion coil I cannot set it that way because there is no zone valve fitted. Also I see in your system there the CH pump is on the flow, on our system the CH pump is on the return pipe inside the outdoor boiler module - in your opinion which do you find best? - do you find pump best on the flow or the return?

Hello thanks for another informative video, I have just moved into a new house, and my system currently has a gate valve on the heating return (which is fully open), and a small section of pipe joining the flow and return which presumably acts as a bypass if all trvs are shut. Currently the rads downstairs are not hot at all, is this because the return gate valve is fully open or is there another possibility? Many thanks for any guidance

Hi fantastic intuitive video but hope you don't mind me asking at 5:40 you say make sure the arrow on the bypass is pointing towards the flow? But the flow heads towards the port valve A and B so surely the arrow points towards the return pipe from the flow 🤔

Very informative, thank you. Is something dripping at @ the 7"00 mark?

Sorry for late response, just discovered this video. Very helpful video, but one question. Will this type of bypass work with a 'Smart Pump' like my Grundfos Alpha 2. With that unit, as the TRV's close down the pump automatically reduces its speed to try to maintain a near constant pressure (so without a pressure rise, what would force the bypass valve to open)? If a system needs a bypass, does it mean that the pump's 'dumb' speed settings must be used?

I know most combis have them built in now. But if the gate valve version is banned now, does that mean having the rad in the downstairs WC not having a TRV to act as a bypass also banned? all the best

Great video, I watched it before installing my valve. It might be because I bought the cheapest valve toolstation had, but is it normal to always have some flow through the valve even when TRVs are open? If my pump is on speed 3 I get hot water going through the valve, even when it's on the tightest setting, and the radiators don't heat up properly but the boiler gets up to temp and switches off. So I put the pump on speed 2 but even when the valve is on the least tight setting, there isn't enough pressure to open the valve when all the TRVs are closed, so it causes a flow error on the boiler. Just can't find a setting where the water only goes to the radiators until all the TRVs are closed.

I know you can have auto bypass valves etc , but could you please do a video on setting up the manual bypass valves please, and also when my hot water and rads are both on it robs the radiator heat away, can you please help, I have already balance the rads etc

Hi Big Al, quick question is the valve fully open at 0.1 or at 0.6? Also my Pump is a Grundfos Alpha2 and I have it set to auto, what setting do you think would be best for the bypass valve? Thanks

the auto bypass valve I have appears to stuck open causing radiators to fail to receive hot feed. Can I replace just the plastic head from a new valve?

Hi when you say you can leave it in the fully open position is that 0.1 or 0.6

Could you replace the gate valve then simply?

Do I need one of these on a combi, I have all trv on my rads?

Hi my loft expansion tank overfills and the ballcock shuts off ok i wonder if this would cure it?

Hi Al, Just had a Worcester External boiler fitted... Me being a little nosy I decide Check it out after they had gone.... grrrr. The boiler has a froststat, They ran a new cable with switched and constant live for the stat....Thought I would check the wiring and guess what, after all the work to run the cable they have not wired the constant live! No Stat... further investigations show they have not fitting auto bypass Valve, so now I am thinking a). they didnt fit bypass to save time and b) they knew they were not going to fit one or run the boiler frost stat, or why would it not be wired in after all that work. If it was wired frost stat would cut in with no bypass valve. would this burn the pump out and destroy the boiler? Greenstar Danesmoor External Regular 18/25...any advice welcome

Hi, i tried the bypass on half a turn and then turned every radiator off and fired up the system, the pump sounded fine and not too noisy, the boiler sounded fine it didn't make any strange noises however i noticed the flame light was out, is this because there is not enough circulation or is it because the heat is not being dissipated anywhere because its only going through the bypass and making the return pipe too hot? The boiler is a worcester 18ri Thanks

Hi, I have a baxi ecoblue 30 system boiler feeding 16 radiators which have Danfoss radiator thermostats. I have installed a Honeywell DU144A1001 to replace the gate valve on my heating system. Any idea how I determine what setting to choose on the new valve?

Does it have to be installed near the boiler/pump? Does bigger loop will make it better or worse? I have TVRs installed (with one radiator on manual setting just slightly open for the winter to allow flow when all TVRs close) and thought about removing radiator in the kitchen (it's always shut), and placing bypass valve instead of radiator. Is it good or bad idea...or just genius or stupid? ;)

Hello I have a y-plan and my boiler is showing FA issue (reverse flow), after changing the pump and the motor in the 3 port valve, this gas engineer spotted a by pass valve in the airing cupboard with some silicon on and he said this might be the problem of the reverse flow but I am adamant to remove it as this must have been there since the house was built 2007 and I don't get why should cause this FA issue if always been there. Basically when FA kicks in, cylinder becomes noisy and heating upstairs become also warm even if heating system is on. I have looked and it seems one radiator has just the valve with plus and minus and the others are trv's, would you reckon removing it might cause a problem?

You talk just about TRV’s, but I guess the same problem occurs when all the zone valves close, and the pump overruns; Is that correct?

is this the same for combi?

There is a valve right after the pump. And there´s a "note" saying there is a separate video on how to renew those, but after spending a good 20 min going through your channel, I was still unable to find what that valve it. Would appreciate if you could enlighten me. Your videos are super helpful, BTW! Really appreciate them!

I have a boiler question for you. My boiler is from the late 70s would it be worth installing one of them electronic smart thermostats that control each rad. Got given a second had one that someone upgraded. So the boiler will come on and off when it needs,would it be a waste? Any help would be great, thanks Stephen

Also to be noted that closer to the boiler the better that if your pump is installed to correct spec. One of the main reasons for an auto bypass valve is that the CH water won't be flowing through the pipe work throughout the house if its 2 pipe system. Less heat loss makes it about 5 to 10 percent more efficient.

I get why you need this on a one pipe system, but do you even need this on a 2 pipe system?

Couldn't you just have taken a trv off and put on a lockshield ?

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Bit confusing because for Y plan setups with a mid position 3 way valve, my boiler manual is saying a automatic bypass is not required. I guess because the mid position valve has a default position of allowing water to hot water circuit even in the off position so this is the bypass already...? Makes sense.