Best air admittance valve
Updated: 23 October 2026
You want one valve for a 110 mm stack in the loft, or one for a short waste branch, and amazon.co.uk is sorting a US fitting with thousands of reviews to the top. That sort key picks the wrong pipe. The best air admittance valve here is the one that states BS EN 12380 for the pipe you have. Prices are amazon.co.uk shelf prices from 19 October 2026, in the [air admittance valve comparison](/hub/diy-supplies/air-admittance-valve). Products Compared did not run a lab test. A qualifying purchase can earn us a commission at no extra cost to you.
You want one valve for a 110 mm stack in the loft, or one for a short waste branch, and amazon.co.uk is sorting a US fitting with thousands of reviews to the top. That sort key picks the wrong pipe.
You want one valve for a 110 mm stack in the loft, or one for a short waste branch, and amazon.co.uk is sorting a US fitting with thousands of reviews to the top. That sort key picks the wrong pipe. The best air admittance valve here is the one that states BS EN 12380 for the pipe you have. Prices are amazon.co.uk shelf prices from 19 October 2026, in the air admittance valve comparison. Products Compared did not run a lab test. A qualifying purchase can earn us a commission at no extra cost to you.
Our top picks
| Badge | Product | Pipe size | Joint | Standard stated | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  FloPlast FloPlast AF110G Push-Fit Air Admittance Valve - Grey | 110 mm; size line also Small | Push-fit | BS EN 12380 A1, KM512474 | 9.0 | about £23.85 | View offer |
| Best value |  FloPlast FloPlast AV40 40 mm Compression Air Admittance Valve - White | 40 mm; listing also says 32 mm | Compression | n/a | 7.9 | about £11.38 | View offer |
| Alternative |  FloPlast FloPlast AF32 32/40/50 mm Solvent Weld Air Admittance Valve - White | 32 mm; adaptor 40/50 mm | Solvent weld | BS EN 12380 A1, KM512474 | 8.4 | about £14.99 | View offer |
Alternative
FloPlast FloPlast AF32 32/40/50 mm Solvent Weld Air Admittance Valve - White8.4/10about £14.99
On this page
What best means here
Best, on this page, means a UK nominal size, a standard written on that listing, and review text about a UK install. It does not mean the largest review count. The top pick is the highest score from these listings. The best value is the lowest price among branch valves whose UK reviews describe a metric waste fit.
The Oatey Sure-Vent is 4.6 from 2,253 reviews and is built for 1.5 inch to 2 inch pipe under ASSE 1050 and ASSE 1051. A UK reviewer says it does not fit 40 mm. The white and black LavaTap 32/40/50 mm pages both show 4.8 from 7, and the written reviews are the same four texts, so those counts are one sample. Size rules are on the buying guide. This page says who each named model is for.
Top pick for a 110 mm internal stack
The top pick is the FloPlast AF110G, ASIN B0059WR0TI, at £23.85 with 4.6 from 251 reviews. The listing states A1 to BS EN 12380, Kitemark KM512474, −20 °C to +60 °C with no insulation required, and use below the flood level of connected appliances. It is a grey 110 mm push-fit at 439 g. FloPlast’s schedule for KM 512474 includes the AF110 code.
Reviewers who name a loft stack often say the smell went within a day once the rubber was lubricated, and the toilets still flushed. Reviewers also say the rubber stiffens later so the smell returns. Spare seals are not described, so the repair is a new valve. The size line also says Small and 1.5 inches, so hold the socket against your spigot. Skip it on a 32, 40, or 50 mm branch. The LavaTap 110 mm at £23.49 does not state BS EN 12380, which is why it is not the top pick.
Best value on a 40 mm branch
The best value is the FloPlast AV40, ASIN B01L4QTA4U, at £11.38 with 4.6 from 80 reviews. It is a white 40 mm compression valve. The listing says the socket also fits 32 mm ABS, polypropylene, and MUPVC, and a bullet says it may be used as a secondary rodding point. Reviewers describe it stopping smell on 40 mm uPVC, and stopping a bath from pulling a shower trap. The rubber is fiddly to keep seated while the nut tightens.
BS EN 12380 and KM 512474 are not stated on this file. If you want that sentence on a branch valve, the AF32 at £14.99 states it, with 4.6 from 56 reviews, a 32 mm solvent socket, and an adaptor for 40 mm and 50 mm. The extra money is the stated standard. Do not put the AV40 on a 110 mm stack. England and Wales guidance keeps these valves indoors.
Listings to skip for a UK metric pipe
Skip the Oatey 39017 on metric pipe. At £12.82 and 2,253 reviews it looks decisive. The page is 1.5 inch to 2 inch, NPT, country of origin USA. UK texts say it does not fit 40 mm and, in one case, that a toilet still flushed badly until the valve came off.
Skip the Operitacx listing at £10.69. The title says 50/75 and two pieces, the unit count says 1.0, and there are no reviews, no joint, and no standard. The LavaTap 110 mm page says internal or external and does not state BS EN 12380. Approved Document H does not allow an ordinary valve of this type outside in England and Wales.
Common questions
Which valve is the top pick for a loft soil stack?
The FloPlast AF110G at £23.85. It states BS EN 12380 A1 and Kitemark KM512474, with 4.6 from 251 reviews. You still lubricate the rubber and check the socket, because the page also says Small and 1.5 inches. It is the wrong valve for a basin branch. One buyer received a unit that closed the vent with a sliding collar, so check the cap you unpack.
Which is the best value for 40 mm waste?
The FloPlast AV40 at £11.38, with 4.6 from 80 reviews, on a compression joint. It does not state BS EN 12380. If you want that line, pay £14.99 for the AF32, which is a 32 mm solvent socket with an adaptor for 40 mm and 50 mm. The AV40 is not a 110 mm stack cap.
Why not the Oatey with thousands of reviews?
The reviews mostly describe 1.5 inch and 2 inch pipe. The listing cites ASSE 1050 and ASSE 1051, not BS EN 12380. A UK review says it does not fit 40 mm. Review count is the wrong sort for a metric waste pipe. Country of origin on that page is the USA, and the thread type is NPT.
Is the LavaTap 110 mm the same buy as the AF110G?
No. Both are about £23 to £24 and both talk about 110 mm. Only the AF110G states BS EN 12380 and KM512474. The LavaTap has 4.3 from 13 reviews and claims external use, which England and Wales guidance does not support. Three short reviews in the file say little about how long the seal lasts.
Is the £10.69 pack a best value?
No. It is the lowest shelf price and has no reviews in the file. The title says 50/75, not a checked 40 mm or 110 mm socket, and no standard is stated. Best value here is the AV40, which has UK reviews of a 40 mm fit. Cheap is not that badge when you cannot tell if the socket fits.
Related pages
Sources
Public UK sources and the amazon.co.uk listings compared on this page. Listings captured 19 October 2026. Updated 22.10.2026.
- Approved Document H (2015), clauses 1.31–1.33 (retrieved 22.10.2026)
- BPF Pipes Group, Air admittance valves for domestic properties, January 2024 (retrieved 22.10.2026)
- BSI, BS EN 12380:2002 (retrieved 22.10.2026)
- FloPlast soil and waste FAQ (retrieved 22.10.2026)
- FloPlast Kitemark schedule KM 512474 (retrieved 22.10.2026)
- Sefton Council, smelly drains note (retrieved 22.10.2026)
- P&H Engineering, Air admittance valves: getting it right (retrieved 22.10.2026)