The best air admittance valves, compared.
Top pick: LavaTap Air Admittance Valve 32mm 40mm 50mm, AAV Waste Pipe Vent, White Best value: FloPlast AV40 40 mm Compression Air Admittance Valve - White – About £11.38 with 4.6 from 80 reviews for a 40 mm compression branch. The page does not state BS EN 12380. Updated 22.10.2026.
An air admittance valve lets air into a soil or waste pipe when a flush pulls a vacuum, then closes so sewer air stays in the pipe. You are usually choosing a 110 mm valve for a soil stack, or a 32, 40 or 50 mm valve for a basin, bath, shower or washing-machine branch. What matters is a declared fit to BS EN 12380 and a joint that matches the pipe. It still expects the drain to relieve positive pressure. The valve does not replace every open vent, and it is not a boiler air vent. See the [air admittance valve buying guide](/hub/diy-supplies/air-admittance-valve/sub/air-admittance-valve-buying-guide). A 110 mm valve does not go on a basin pipe. Solvent weld needs cement, and the file does not give a cure time. UK nominal bore is not the outside diameter. LavaTap’s listing says 32, 40 and 50 mm pipe measure roughly 36, 43 and 56 mm outside.
An air admittance valve lets air into a soil or waste pipe when a flush pulls a vacuum, then closes so sewer air stays in the pipe.
28 products checked · 56 hrs invested · +21,400 readers
Swipe for more
1-2 of 8
Personal buying guide
Question 1 of 2
What pipe are you capping?
LavaTap’s white 32/40/50 mm valve is £14.99, with a headline of 4.8 from 7 reviews. The listing describes a 32 mm solvent socket and a stepped adaptor for 40 mm or 50 mm, for indoor basins, sinks, baths, showers and washing machines, fitted upright above the highest trap, and it says the valve does not replace the main stack vent. A seller note says those nominal bores measure roughly 36 mm, 43 mm and 56 mm outside. The four written reviews praise the three sizes, a fit on Osma solvent-weld pipe, a small space, and one case where it worked after a more expensive brand failed. Those same four texts appear on the black ASIN, so you should not add the two star counts together. BS EN 12380 is not stated, and the weight field prints 0.9 g against a body of 5.8 × 5.8 × 10.5 cm, which is not a usable mass. One buyer fitted it outside, which the bullets do not recommend. It is a compact indoor branch option if you want the adaptor pack and will accept a thin, shared review file.
Pros
Cons
Best for: You want a white indoor adaptor valve for 32, 40 or 50 mm solvent waste and you can ignore the shared star line.
Less suitable: You want a Kitemark on the page, a 110 mm stack, or an outdoor termination.
Specifications
Common questions
Will it fit 32 mm, 40 mm and 50 mm waste?
The listing says the valve fits a 32 mm solvent socket and the stepped adaptor takes it to a 40 mm or 50 mm socket.
Can it replace the main soil stack vent?
No. The listing says it adds a vent to a branch and does not replace the main stack vent. Fit it upright and indoors, above the highest trap it serves.
Is it for a shower or washing machine?
Yes, the bullets name basins, sinks, baths, showers and washing machines indoors. A WC is not named.
The black LavaTap is the same £14.99 branch valve in a black finish, with 4.8 from 7 reviews and the same four written texts as the white ASIN B0FWRZZMWR. The bullets again limit it to indoor basins, sinks, baths, showers and washing machines, upright and above the highest trap, and they say it does not replace the main stack vent. The pack is a 32 mm spigot plus a 40/50 mm stepped adaptor, and the page again prints 0.9 g, which is not a usable mass next to dimensions of 5.8 × 5.8 × 10.5 cm. No separate defect is reported for the black colour, and no BS EN 12380 line appears. The listing date in the file is 27 April 2026. Choose it when the pipe run is black and you are buying the same indoor adaptor valve as the white page, not because the seven ratings are a second independent sample. Skip it for a 110 mm loft stack and for any outdoor termination in England or Wales.
Pros
Cons
Best for: Your waste pipe is black and you want the indoor LavaTap adaptor, knowing the reviews are shared with the white listing.
Less suitable: You need independent reviews, a stated UK standard, or a 110 mm soil valve.
Specifications
Common questions
How does the black valve differ from the white one?
The listing colour is black. Size, price (£14.99), adaptor and indoor-use bullets match the white LavaTap 32/40/50 mm valve. The written reviews in the file are the same texts.
What joint is it?
A 32 mm solvent spigot with a 40 mm/50 mm stepped adaptor in the box.
Does the listing allow outdoor fitting?
The bullets say indoors. One review describes an outdoor fit. That review is not the listing instruction.
The Oatey 39017 Sure-Vent is £12.82 with 4.6 from 2,253 reviews, sold for 1.5 inch to 2 inch pipe with a PVC adaptor. The listing cites ASSE 1050 and ASSE 1051 plus the IPC and UPC, and it does not state BS EN 12380. It says the valve vents up to 160 DFU on a branch or 24 DFU on a stack, which is US drainage-fixture language, and the country of origin is the USA. Most of the praise is from the United States, Canada, Mexico and Spain: gurgling sinks and tubs on imperial pipe, and an adaptor that steps 1.5 inch and 2 inch. A UK review says it does not fit 40 mm pipe. Another says the toilet still did not flush correctly until the valve was removed, and a Spanish review says the sizes are not European. The thread type is listed as NPT, with inlet solder and outlet NPS on the attribute block, so the joint is not a UK 40 mm solvent or compression socket. The star count is the largest in the set, and it is still the wrong buy for metric UK waste or soil pipe.
Pros
Cons
Best for: You are repairing a 1.5 inch or 2 inch imperial DWV branch and you want the ASSE valve Oatey lists for that pipe.
Less suitable: Your pipe is 40 mm or 110 mm UK plastic and you need BS EN 12380.
Specifications
Common questions
Will this Oatey valve fit 40 mm UK waste?
The listing size is 1.5 inch to 2 inch with a PVC adaptor. A UK review says it does not fit 40 mm pipe. BS EN 12380 is not stated.
Which standard does the listing cite?
ASSE 1050 and ASSE 1051, plus the International Plumbing Code and the Uniform Plumbing Code. It also quotes 160 DFU on a branch or 24 DFU on a stack.
Is it for a shower?
A shower is not named. The bullets describe it as an alternative to a secondary vent in a DWV system.
The FloPlast AF110G is a grey 110 mm push-fit air admittance valve at £23.85, with 4.6 from 251 amazon.co.uk reviews. The listing states A1 approval to BS EN 12380, Kitemark KM512474, a range of −20 °C to +60 °C with no insulation required, and use below the flood level of connected appliances. Reviewers who fitted it on a loft soil stack often say the sewer smell went within a day, the socket felt snug on 110 mm pipe once the rubber was lubricated, and the toilets still flushed. The same reviews say the rubber fin is tight and the instructions do not explain that the seal can come off. Rubber that stiffens later is a repeated complaint, and spare seals are not described as available, so those buyers replace the whole valve. One buyer reports a unit that closed the vent with a sliding collar and did not work as an air admittance valve, with the seller query ignored. The size line says Small and the outlet connection is listed as 1.5 inches, so you should check the socket against your pipe rather than trust every size field. In this set it is the top pick for an internal 110 mm stack where you want the standard stated on the page, and the wrong valve for a 32, 40 or 50 mm basin branch.
Pros
Cons
Best for: You are capping an internal 110 mm soil stack and want the BS EN 12380 and Kitemark sentences on the amazon.co.uk page.
Less suitable: Your pipe is 32, 40 or 50 mm waste, or you need a spare rubber seal rather than a whole new valve.
Specifications
Common questions
What pipe does this FloPlast valve fit?
The listing describes a grey push-fit air admittance valve and states A1 approval to BS EN 12380, including use below the flood level of connected appliances. The size line says Small and the outlet connection size is listed as 1.5 inches, so check the socket against your 110 mm soil pipe before you order.
Does the listing say it is tool-free?
Tool-free is not stated. The inlet connection is push-fit, and reviews mention lubricating the rubber seal.
Is a shower or washing machine named?
The bullets do not name a shower, a WC, or a washing machine. Reviews describe loft soil stacks.
The FloPlast AV40 is a white 40 mm compression valve at £11.38, with 4.6 from 80 reviews. The listing says the compression socket fits 32 mm ABS, polypropylene and MUPVC as well as the 40 mm size it is sold as, and a bullet says it may be used as a secondary rodding point. Reviewers describe it stopping drain smell, fitting 40 mm uPVC waste, and stopping a bath from pulling the water out of a shower trap on a shared branch. One buyer uses it on a Saniflo to stop smell in the room. The internal rubber is the recurring snag: it is difficult to keep seated while you tighten the nut. BS EN 12380 and Kitemark KM512474 are not stated in this file, so it does not inherit that sentence from the AF110G or the AF32. One review hopes it will survive outdoors, which is not a listing claim, and another review is about a belt and does not describe the valve. At this price it is the best value in the set for a short 40 mm waste you can reach, and a poor match if you need the standard stated or a 110 mm stack cap.
Pros
Cons
Best for: You want a reachable 40 mm compression valve on a waste branch and you accept a listing that does not state BS EN 12380.
Less suitable: You need a stated Kitemark, a 110 mm soil stack, or a solvent-only joint.
Specifications
Common questions
What does the AV40 connect to?
It is sold as a 40 mm compression air admittance valve. The bullets say the compression socket also fits 32 mm ABS, polypropylene and MUPVC.
Does this listing state BS EN 12380?
No. BS EN 12380 and a Kitemark number are not in this file.
Can it be a rodding point?
The listing says the air admittance valve may also be used as a secondary rodding point to remove blockages.
The FloPlast AF32 is a white solvent-weld valve at £14.99, rated 4.6 from 56 reviews, for 32 mm UK pipe with an adaptor for 40 mm and 50 mm. The listing states A1 to BS EN 12380, Kitemark licence KM512474, and −20 °C to +60 °C with no insulation required, and it says the valve may sit below the flood level of connected appliances. Reviewers praise the three sizes in one pack and describe decent ABS that stops waste glugging when they wanted a separate valve rather than a trap with a built-in vent. The joint is solvent weld, so it is not a tool-free push-on, and this file does not give a cement cure time. One buyer reports the seal failing after a month or two and fitting another brand. Country of origin is listed as the United Kingdom, the warranty line is two years, and the weight is 83.6 g. It is the branch valve in this set that states the Kitemark, which is the reason to pay £14.99 instead of the cheaper AV40, and it is the wrong object for a 110 mm soil stack.
Pros
Cons
Best for: You have 32, 40 or 50 mm solvent waste and want the Kitemark sentence on the branch valve itself.
Less suitable: You need a 110 mm stack cap, or a compression joint you can undo without cutting the pipe.
Specifications
Common questions
Which waste sizes does the AF32 cover?
The listing says it fits 32 mm UK pipe directly and 40 mm or 50 mm pipe with the adaptor supplied.
What standard does this listing state?
It states A1 approval to BS EN 12380, Kitemark licence KM512474, and a range of -20°C to +60°C with no insulation required.
Is the joint tool-free?
No. The connector type is solvent-welding. A cure time is not given in the file.
LavaTap’s 110 mm valve is £23.49, with 4.3 from 13 reviews and only three short texts in the file, which say it stops smells and is easy to fit. The listing describes a female socket for 110 mm male pipe, push-fit or solvent weld, and a rubber lining for tool-free installation. It tells you to install the valve vertical, at least 200 mm above the highest flood level, and it names kitchen islands, lofts, basements and multi-storey stacks. The same bullets say internal or external use. BS EN 12380 is not stated, and colour and included items are not stated. At 270 g and £23.49 it sits next to the FloPlast AF110G on price without the Kitemark sentence that listing carries. Treat the external sentence as a product claim, not as permission under Approved Document H for England and Wales. It is a possible 110 mm cap only if you have checked the standard yourself and will keep it indoors and reachable.
Pros
Cons
Best for: You already know you need a 110 mm indoor cap and you will not treat the external sentence as the building-regulations rule.
Less suitable: You want BS EN 12380 stated on the page, or you plan to fit the valve outside.
Specifications
Common questions
What stack size is this LavaTap valve for?
The listing says a female socket accepts 110 mm male pipe, for push-fit or solvent weld, and says to install it at least 200 mm above the highest flood level.
Does the listing say it can go outside?
Yes. It says internal or external use. It does not state BS EN 12380.
Is installation described as tool-free?
Yes. A bullet says the rubber lining allows tool-free installation on 110 mm male pipe.
Operitacx lists a white PVC air admittance valve titled 50/75 at £10.69, with dimensions of 8.8 × 8.8 × 10 cm and a weight of 240 g. The saved listing has no customer-review line, no connection type, and no BS EN 12380 or Kitemark sentence. The title says two pieces while the unit count is 1.0, and the model number is a catalogue string rather than a plumbing code you can match to a Kitemark schedule. The bullets repeat negative-pressure and water-seal claims without a standard number, and the country of origin is China. At 50/75 in the title it is neither the 32, 40 or 50 mm UK waste set nor a 110 mm soil valve. With no reviews in the file, you cannot tell whether the socket fits the pipe in your hand. It is the cheapest listing here, and it is the one to skip when you need a stated UK size and a standard you can check.
Pros
Cons
Best for: You have already measured a 50 mm or 75 mm socket against this fitting and you accept a listing with no reviews.
Less suitable: You need a checked 40 mm or 110 mm UK valve with a standard on the page.
Specifications
Common questions
What size is the Operitacx valve?
The title says 50/75. The connection type is not stated. Dimensions are listed as 8.8 x 8.8 x 10 cm and weight 240 g.
Does the listing name a standard?
No. BS EN 12380 is not stated, and the saved listing has no customer-review line.
Is it for a WC or a shower?
Neither is named. The bullets only repeat a negative-pressure and water-seal claim.
Not a laboratory test. Scores use the amazon.co.uk listings captured for this set on 19 October 2026: shelf price in GBP, star rating, review count, whether the page states BS EN 12380 and a Kitemark you can match to the product code, whether the pipe size is UK metric, and deductions for shared reviews, non-UK review bases, missing standards, listing conflicts and no reviews. A stated UK standard and a matching pipe weigh more than a raw star line. The highest score is the top pick. Best value is the lowest shelf price among branch valves whose UK reviews describe a metric waste fit. A cheaper listing with no reviews does not take that badge.
Stated UK standard
30%A page that states BS EN 12380, and a Kitemark you can match to the product code, scores above a star line. Only the AF110G and the AF32 state KM512474 in this set.
Pipe size and joint
25%110 mm for a stack, or 32, 40 or 50 mm for a branch, with push-fit, solvent weld or compression that matches the pipe. A US inch size is marked down.
Review evidence
25%Stars and how many reviews sit behind them, with deductions when the texts are shared across two ASINs or the sample is mostly outside the UK.
Listing conflicts
10%A size line that disagrees with the socket, an implausible weight, a missing joint, or no reviews at all, is a deduction.
Price for that job
10%Best value is the lowest shelf price among branch valves whose UK reviews describe a metric waste fit. The dearest stack valve can still be the top pick.
Buy the pipe size and the stated standard before the star rating. A 110 mm valve finishes a soil stack. A 32, 40 or 50 mm valve sits on a waste branch. The joint is push-fit, solvent weld or compression. In England and Wales the valve stays indoors, upright and reachable. It does not replace every open vent, and it is not a boiler air vent.
An air admittance valve lets air into a soil or waste pipe when a flush pulls a vacuum, then closes so sewer air stays in the pipe. It is not a boiler air vent and it is not a compressor check valve. You are usually choosing a 110 mm valve for a soil stack, or a 32, 40 or 50 mm valve for a basin, bath, shower or washing-machine branch. A 110 mm valve does not go on a basin pipe. Some FloPlast solvent sockets are 82 mm. None of the eight listings here is that size.
The Oatey Sure-Vent has 4.6 from 2,253 reviews and is sold for 1.5 inch to 2 inch pipe. A UK review says it does not fit 40 mm pipe. BS EN 12380 is not stated.
The valve needs to sit upright, with air around it, where you can remove it. England and Wales do not allow it outside or in a dust-laden atmosphere. Loft insulation fibres are a known reason valves stick.
An air admittance valve is not a boiler air vent and not a compressor check valve. It does not clear a blocked drain, and it must not be the only vent to a septic tank or cesspool.
Nominal size is the first cut, and it is not the outside diameter. A soil stack in this set is 110 mm. A basin, bath, shower or washing-machine branch is 32, 40 or 50 mm. A 110 mm valve does not go on a basin pipe. The FloPlast AF110G is the 110 mm push-fit with BS EN 12380 stated. Its size line still says Small, and the outlet is listed as 1.5 inches, so you check the socket against the pipe. On branches, the FloPlast AF32 is a 32 mm solvent socket with an adaptor for 40 mm and 50 mm.
The standard to look for is BS EN 12380:2002. Approved Document H clause 1.33 uses it for England and Wales. Scotland’s domestic Technical Handbook 3.7.8 and Northern Ireland’s Technical Booklet N point at the same standard. A1 on a box is trade shorthand for designation A and temperature class I. A means the valve may sit below the flood level of connected appliances. B means it may not. Class I is −20 °C to +60 °C.
Three typical situations, each with a recommendation from this comparison.
You are capping an internal 110 mm soil stack and you still need a way for the drain to relieve positive pressure. The FloPlast AF110G is the top pick at about £23.85. The page states BS EN 12380 A1 and Kitemark KM512474, with 4.6 from 251 reviews. Check the socket: the size line also says Small and 1.5 inches.
A bath, basin, shower or washing-machine branch is gurgling, and a blockage is already ruled out. The FloPlast AF32 is about £14.99 for 32 mm solvent waste, with an adaptor for 40 mm and 50 mm. It states BS EN 12380 A1 and KM512474, with 4.6 from 56 reviews. It is the wrong valve for a 110 mm stack.
You want a compression joint you can undo, and you accept a listing that does not state BS EN 12380. The FloPlast AV40 is best value at about £11.38, with 4.6 from 80 reviews. The bullets also name a secondary rodding point. It is a poor match for a 110 mm stack or a stated Kitemark.
The top pick is the FloPlast AF110G at about £23.85. It scores 90, the highest here: a grey 110 mm push-fit valve, 4.6 from 251 reviews, with BS EN 12380 A1 and Kitemark KM512474 stated. Rubber that stiffens, and a size line that also says Small and 1.5 inches, are the deductions. Best value is the FloPlast AV40 at about £11.38, with 4.6 from 80 reviews, for a reachable 40 mm compression branch. That page does not state BS EN 12380. The Operitacx listing is cheaper at £10.69 and has no reviews in the file, so it does not take the badge.
FloPlast AV40 40 mm Compression Air Admittance Valve - White
About £11.38 with 4.6 from 80 reviews for a 40 mm compression branch. The page does not state BS EN 12380.
Editorial
Peter F. is the editor for DIY & tools at productscompared.co.uk. Comparisons in this category are checked against amazon.co.uk listings, review evidence and public UK sources.
Guides on what to look for, how to use a product, and common mistakes.
Public UK sources and the amazon.co.uk listings compared on this page. Listings captured 19 October 2026. Updated 22.10.2026.
This page contains affiliate links. If you buy through them, we may earn a commission at no extra cost to you. Links to amazon.co.uk use the tag pcuk26-21. Prices, stars and review counts are the figures already stored for this set. This is not a laboratory test.
