HOW NON RETURN VALVES WORK - Plumbing Tips 

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I've had this problem for years and always wondered why I had this problem with hot and cold water in bath's and sinks. Job for the weekend now is fitting NRV's to the taps. Thanks for this great video.

Showers with poor hot and strong cold pressure. I saw this video B4. Got to my sister's house and had a nightmare controlling shower. Thought hang on... I've seen summat. RU-vid a refresh and boom. The video was even better 2nd time round! That's the shower sorted

That is so helpful! Your little video has answered so many questions.

Non return valves fitted on inlet hoses of appliances (dishwasher/washing machines etc) is a great idea and can prevent unpleasant, yet harmless, taste and odours occurring at drinking water taps. Chlorine in mains fed water can react with phenols that are present in some rubbers and plastic fittings (appliance hoses, flexi tap tails, phenolic rubber tap washers). The reaction produces trichlorophenol, more commonly known as TCP. A very distinct taste/odour, which unlike chlorine, will persist even in boiled water and is still detectable in tea and coffee. It's harmless, but who wants top in their tea? Fitting NRVs to appliance hoses is a great step to help reduce such tastes/odours. Note, most appliances will have some backlogs device within the appliance itself, but it's good practice to install on the mains feed side of the inlet appliance hose to tackle the affects of water sitting in the hose itself. Great vid re hot/cold imbalance. I think difference between single and double check valves is that a single check valve contains just one sprung loaded valve. A double check valve has two individual sprung loaded valves, sometimes with a test port between the two.

Can you comment on the pressure loss in these things .

Hi mate .. I have a problem with a mixer tap spluttering on HW side .. it has a non return valve fitted Many thanks for your help

I'm wondering if I should put one of these below my toilet. When my washing machine suddenly uses the water inlet or I use the sink next to it, my toilet inlet seems to have back pressure, as it makes the shut off valve suddenly start trickling water though and it is no longer shut off.

Cats are cool. I have a tabby (Harry), and as long as you remember that he is in charge and owns the neighbourhood - then everything will be fine and dandy. Oh, and also remember - dogs have owners, cats have staff. Remember these things and your cat may just let you smooth him. LOL! Thanks for another great vid.

I changed a mains cold water electric shower to an inbuilt power shower using cold water tank and hot water cylinder ( with surrey flange ). Due to location of bathroom / hot water tank the only practical route was across the loft space from the tanks. The prob is that after a few days, the hot water pipe starts to contain air ,and the pump spins dry intermittently until it grabs a steady supply of hot water. and then its's ok for a few days.

Very interesting as usual. Many thanks for the video. I have a non return valve fitted outside on the pipe leading to my outdoor tap. Throughout the cold months (which seems like far more than the warm ones!) I turn off the ball valve on the inside as I should to prevent very unwanted burst pipes outside. I turned the valve on for the first time in 3 or 4 months and all I got was a trickle from the outdoor tap! It can't be the valve that's the issue as that turns easily. Is it possible that the non return valve has seized? Is that possible? If so, do I have to replace it... OR is there a simpler solution?

Does a Non Return Valve always go after an Isolator valve? or can you fit an Isolator after the NRV? I suppose if you ever have to replace the NRV you can atleast isolate it locally.

Enjoying your videos! Thanks for your channel. When you drew the plumbing schematics, the symbol for the one-way valve is the same as that for a diode in electronics. That reminded me of the many similarities between plumbing and electronic theory. Good show! Roy Lewis. Buffalo, NY USA

dig the way ya break it down simple every time..love the cat.like the way they spazz out randomly for no apparent reason...clawing and bouncing off stuff!

Would reducing the cold water pressure with a balancing valve achieve the same job?

on a macerator ? to prevent smells or backwash to a sink and /or shower running into a macerator ?

Check valves often double are required to stop backflow from dishwashers , washing machines out side taps etc which judged to have a fluid 3 risk which is all of them?). I have noticed that water suppliers are doing more inspections and its what is coming out in improvement notices is lack of double check valves. I have had three customers this week contact me about this and they have all been given 3 week improvement notices

Basically have a job which has gravity system and a grundfos 2bar pump running 2 showers. Keep getting airlock in the system and when the hot tap in the kitchen is opened the pump kicks in and the pumps squeals because of the air in the system. I have been advised by grundfos to fit 2 low pressure non return valves on the outlets from the pump to solve this problem. Does this sound correct to you?

Good video, thanks. Can you advise me before I 'LOSE IT?' Moved my Auto mixer tape from my Appartment to my house, never had a problem until I did that, water started to exit the over flow, advised by a plumber to fix these, just done so now only hot water coming out & that is at a reduced rate! The arrows are facing the take on both pipes. Seems like I can't win, this is winding me up so much. Thanks

Im thinking of using a non-return valve on the hot for mixing solar hot water into a cold feed only washing machine. Is this smart? Will use valves to set the temperature to 30*C.

Thank you, I wasn't clear how these worked and how it would benefit my home. Now I understand how they work I can confidently specify a non return valve in every hot supply pipe where a mixer tap or shower mixer occurs. PS I'm allergic to Cats.

Would you use that for an outdoor tap and Infront of a toilet cistern

Do I need a NRV on a cistern? Are there isolation valves with built in NRV?

Thanks for that. Helped me work out what was going on. Great presentation. Cheers from Australia.

Fab! Can an instantaneous electric hot water heater outlet be fed into an existing hot pipe coming from an electric immersion tank with one of these valves to stop the water from the immersion tank flowing backwards through the instantaneous water heater? I want to shut off the immersion tank feed and supply my basin and mixer-tap shower in the bathroom mostly with the instantaneous heater, but I also want the option of putting the immersion tank back on when I'm really stinky and fancy a bath (There's a big shiny red tap on the pipe from the immersion tank, so it'd be easy to use that to switch between bath mode and shower mode) ..If what I've just written there makes sense.. Good luck deciphering it!

I want to put a Salamanda home boost coz my shower pressure poor and mains pressure the cause. I was told I can install it on my cold water feed to my combi bit would need to install non return valves on all other sources using the cold water before it gets to the combi. But not sure where to position them. Any advice on this? Thanks

Can you add a Non-Return valve to the hot water outlet pipe connected to the boiler, avoiding having to have multiple non-return valves at every tap?

Thanks that has explained why my rental property has these in the washbasin supply pipes to the mixer tap and why they are not needed for separate taps. I do get some vibration though if the hot tap is open only a small amount. Is this the non return valve open/closing?

We had a new Boiler fitted a few months ago. At the time we noted the boiler was kicking in when the engineer turned on the cold water tap in the kitchen. We asked why this was happening and the engineer said this was normal. This has increased our energy bill as the boiler kicks in every time that cold water tap is fully on; boiler doesn’t kick in if tap is running slowly. Now the engineer is saying the problem is with our tap and 2 non return valves need to be fitted at our own expense. Is this reasonable?

I installed a non return valve last year on a outside tap and it was working fine. I needed to use the tap just now and I have no water coming out of the tap. I've opened the little nut in the middle of the valve and water came out. The valve is the correct way. Is this normal?

does a toilet water feed need a double check valve installing?

Another great demonstration, and very entertaining. Next time you put one of these in a plastic pipe, I'd like to see that done. By the way, Most of the water heaters in my homes are under mains pressure, so pressure should be equal on both sides. Evidently that isn't the case everywhere. Why?

Is that might be the reason why you're shower mixer makes whistling sound when turn on cold water?

Hi hope you can help... I have a mixer tap in the kitchen, bathroom and a thermostatic shower and bath tap, will fitting one double check / non return valve on the hot water out of the boiler be serficiant to stop the cold back feeding on the whole hot water side of the system?

Nice vid. Would you suggest putting a non return valve on a washing machine cold in flow or is it unnecessary?

Bra! Check Valve and Non Return Valve the same thing?

What if I have a tankless gas water heater and the hot water goes to several mixer tap, where would I put the non return valve ?

I've got a check valve on my hot water bath tap from the check valve to the tap connector is a push fit connection water is leaking out of the push fit connector??? Any idea how to connect the check valve to the tap connector so eliminating the push fit problem?

Thank u , I used it on a water filter too , I didn’t know it pushed up into hot pipe , thank u very much

Hi mate could you please advise me on this issue... I have thames water supply and i was going to close my main valve which is located outside but I saw a small white stick and inside the whole of the stick there was a screw, nothing to rotate like I have seen in many videos... Could you please advise me if i have to rotate that screw or it's something else ???

very clear and most helpful with a small injection of humor brilliant. Mark

Thx for this video especially the theory side. I just discovered when I empty my bathroom sink it starts to fill the bath through the plug hole. So I need a 40mm NRV on the waste pipe I guess.

HI, My mate was saying about fitting these to the mains feed to his washing machine, to stop any grotty water sitting in the pipe circulating back along and into the sink taps as its drinking water. However wouldn't mains pressure prevent this from happening in the first place?

Why did you not ream the inside of the pipe after you had cut it with a pipe slice?

Hi Mate, thank you for your video very nice work, just one question; on some valves I've seen a hex screw in the middle and wondered what it was for, could it be to allow a small amount back? would appreciate your answer, thanks

Will these work for air ?. I have a large water tank in my van , fitted with a immersion to heat it up in winter to stop it all freezing (window cleaner ). The tank has a breather on the lid that I’ve fitted ,it’s 3/4” . I wondered if I could use one of these to allow air into the tank (tank should suck when water is draining ) whilst I’m using the water so it doesn’t air lock but stop the evaporation leaking out of the tank and turning the van into a sauna in a morning . Any advice is welcome

Hi, is the check volve only for hot water or for both hot and cold water...?

Shoulld a NRV be fitted on appliance waste pipes to stop backflow of dirty water?

Would the pressure from the cold stop the hot water from coming out the tap even with the valve fitted

Good video clips! Whats the difference between a single check valve and double check valve? Thanks

REALLY helpful tips. many thanks. we recently had our kitchen remodeled and the kitchen fitter really did not have a clue about plumbing! Is it a legal requirement to have a non return valve on the pipework leading to an outside tap? ALSO....is it legal to use lead solder on domestic pipework leading to a kitchen sink tap? cheers marc

Good video, aren't you meant to fit check valves, in the mains cold pipes, to prevent back siphonage, although a plumber said it wasn't neccessary as the mains water pressure would prevent back siphonage but what happens if there is a negative pressure in tge mains caused by broken pipe

Thank you 🙏🏾

Hi James Videos excellent keep them coming. A quick question , why did you not use a paste with the compression fittings? I have noticed in the past you sometimes used ptfe and others a paste ? Just wondering thanks Mark

Hi plumber parts, I've got a overflow pipe leaking which is in the loft next to the other tank. It's the hot water tank. I've got a condensing boiler/system boiler. It's only 4 years old. Its not the floater in the tank and I've had that checked and it's working fine but it's still overflowing and water coming back up the system. We have a mixer tap in the kitchen that as already there. We've just had the bathroom done and there was 2 seperate taps on a sink and swapped with a mixer tap. Could this be why my overflow tank is leaking and would these none return valves stop this issue?

What about a NRV where bath and basin use the same waste pipe. How to stop basin water flowing back into the bath? Waste pipe is almost horizontal,

Is it common to have a non return valve on both the cold and hot outlets or only on 1 pipe such as the hot water outlet

Could you not put a pressure regulator into the cold feed to reduce the pressure to match the pressure of the hot feed.?

You could do without the non return by simply partly closing the ball valve on the hot feed. I would have done this even with the non return. It makes the mixer tap flow easier to balance.

Can you install a non return valve for salamander pump pipework, shower works but after a minute when used a while ago? Presuming that the water from the shower head is running back when turned off.

Good morning, I'm fitting a new stop cock and a non return valve, can I put the valve either side of the stop cock?

If you were to place the Non-Return valve on a supply with low water pressure (in this case the hot water supply), won't the supply with the highter pressure (in this case the cold water supply) stop the non-return vavle from opening and supplying the tap with hot water? In other words, can you have both the hot and cold water running at the same time...won't the cold water supply stop the hot water because of the higher pressure of the cold water supply?

Hi buddy i have a redring expressions 500s shower its has stoped getting hot the other day but copper tank inside stays hot overload light dose not kicking but it just runs slightly warm to touch but still cold what could the problem be

Hi there, I fitted a unvented boiler to my system plus new bath and bathroom sink. The only way I can get hot water at the sink mixer tap is when I turn the bath tap on. When I switch off the bath tap the water runs cold in the sink. Question is do I fit a nonreturnable valve in the hot water side of the sink.

Great video I am fitting a bath mixer and having trouble. The mixer has no fittings supplied so I put loads of ptfe on a 15mm compression elbow. It works but was weeping. I removed elbow and fitted a straight 15mm service valve. I thought it was because the thread was not long enough so I tried male straight connectors and it still weeps? Is there any other fittings to use?

Nice and clear mate, thanks

Can you advise me having finished soldering my pipes if one is not satisfied can you go back and reheat and run the solder round once more.Reason I feel I may not have heated the pipes enough as I have had pipes leak years ago scrapped them no problem . Need more practice I think ! thanks bob.

Hi, I live in a townhouse and we recently installed individual meters to all 50 units. We have existing pressure valves (25) now we are being told that we need 25 more pressure valves installed near the geysers because if the geysers blow the insurance wont cover these..we since removed the sensor meters until we get more information to reinstall them. Can you advise on this please..

im finishing my 6129lvl2 in october hopeing to do my lv3 and gas after christmas your vidz r mint and make the plumbing world worth while keep up the gd vids m8

A thought.. would you need a non-return on the inlet to a toilet cistern? Or would would you get an isolation valve that incorporates a non-return??

Can u please suggest something for my new washing machine which is not taking in water seems as though water at the wall outlet is not coming through what could be wrong plz help,

I shall thank you for your video... Actually, you made me plan to fix a returning water issue in one of my customer's shower pump... Welldone Broth...

Saved my life my wife was in the shower i turned the Tap on in the kitchen she was mad as F**k when cold water came out the shower lol.

Nice clear vid. I have a 15 mm double check valve on the hot and cold lines to my mixer tap. There is a screwdriver slot on the side of the valve that I thought may be for isolating the tap. After I got a bit wet I found that it is not for isolation, it just appears to cap a hole in the side of the valve. Can you tell me what it is for?

Good videos. I have a non-return valve on the boiler filling loop (Sime 80E). Can I simply disconnect the loop from the valve or will water pour out. It does not seem possible to turn off the non return valve

Wow this is a well presented and helpful video. Thank you for generous and free help.

Thanks for the video. I just bought a new expensive tap like this one, thinking the old one was just a cheapo thing because it made horrible noises when opening the cold (which runs off the mains). Turns out it isn't the tap that's at fault as the new one does it. Will a non-return valve sort out this horrible noise? It also runs on a bit after I turn off to empty itself. Thanks

If I’m using my kitchen sink downstairs ,running the water , and someone is having a shower upstairs , it interrupts the flow of water. Would I need to install a NRV as well? And if so does anyone know where I would need to install one?

Hi. I have a NRV fitted on my system. It's in 22mm and I noticed it has a test point on it. What is this 'point used to actually test, and how would you go about it? Cheers.

great video.i installed a new mixer tap in then kitchen and i could work out why water was pouring out the over flow on the roof.it seems cold water was being pumped into hot water system.i need to fit a none return valve.thanks

I have a power shower where the hot supply was installed by routing up from the tank into the loft and back down to the shower. When I turn the shower on it pulls air to start with and eventually water. I know the real solution is to re-route the hot supply, but thats a big job. Would a non return valve on the hot supply work, to stop the water returning back to the tank when the shower is switched off? Perhaps placing it as close to the tank to minimise the air? Thanks

Surprised you called it a SINK when it's a BASIN. A plumber stated that to me once when I phoned the shop. Thanks.

Say if there was a combi system and every time the hot is drawn downstairs whilst the upstairs hot Is drawn at the same time, the hot upstairs loses pressure, I was thinking earlier surely if I install a non return valve this will stop happening but just wanted to know if I’m thinking it through right or not 😂 @plumberparts

It's not practical to run the hot water pipe low level into the bathroom due to the upheaval that would entail, so have in fact fitted a non return valve at the bottom of the vertical drop just above hot water cylinder exit, and it works fine. No more air after a couple of days

Ok so I have a combo boiler and when the toilets are flushed the boiler fires up after the cistern has filled up... Only for like 30 secs.... Any ideas? I've heard about fitting a non return valve to the cold supply to the boiler?

I have one query...! I want to install a mixer in my sink where i have two connection 1) Drinking Water and 2) Non-Drinking Water( for washing purposes) Scenario is Drinking Water pipe comes from out side(from Water Corporation) Non-Drinking comes from our storage(which is taken from borewell not all for drinking) In my sink there instead of two tap's(one for Drinking and other for Non Drinking) i want a single tap which serve the purpose of both! But, our plumber said as the Non-Drinking Water may get mixed with the Drinking one this mechanism fails but, i said use two non-return valves on both the pipes, but he said the Drinking Water pressure is really low and non-return valve will make it even more slower . Is this true? what you can suggest in this situation? Cheers,

What’s the difference between a double and single check valve?

Great video thanks

Is a single check valve the same as a non-return valve?.. And when would you need a double check valve?

learnt a lot from you I did plumbing long time ago trying to get back into it

Hi this is a question regarding one of your other videos I am a complete beginner I want to fit a shower but the hot water pressure is non existent I'd seen on your other Video about using a pump my question is can I use a twin pump but block of one end as I only need the hot water may be a stupid question but I am a complete beginner? Cheers Dave.

Would a 22mm non rtn valve in the vertical drop to HW tank stop this ?

All cats are divas. Great advice about non return valves, will have a go myself as only getting warm water upstairs but hot downstairs.

Hi mate me again.Good idea never thought popping out now to get one cheers great job keep the good work up hope the wife doesn't mind you taking her home apart, take mate thanks !.

On another note. Dude, our kitchen hot tap runs really slow (recent kitchen fit, contractor plumb & fit) where as tother taps are reet. tap's not blocked, as cold is OK, isolations are OK too, full on. What the f**k could be the problem? Yours truly, much love.

what is the difference single and a double check valve

Hi there and thank you for your very informative video. My problem is the following: I knew I had to fit a non-return valve to the hot water feed to prevent backflow. Unfortunately, like in your video, the water pressure of the mains far exceed the one from the hot water (Tank in the loft) which prevents a good regulation for the temperature. Do you have any suggestions? I have already changed the cartridges for kitchen taps thinking that it was the problem but no luck. Would a dual flow tap solve the problem? I understand that with these taps the mixing of the water happens in the spout. I greatly appreciate any help or suggestions.

Excellent video. Thank you!

Beautiful keep up the good work

Is there any 'plastic' parts inside the NRV that hot water will damage? or are there special hot water NRV? Thanks.