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How to fit a gas regulator

Updated: 23 October 2026

You already have the regulator and the cylinder, and you want to know how to fit a gas regulator without guessing the twist. On UK barbecues the motion depends on the valve. A POL nut, a clip-on head, and a 4.5 kg butane screw thread are three different joints, and one clockwise instruction will tighten the wrong one or wreck the right one. This page is the sequence and the soap test only. Matching the millibar rating is already decided on the main [gas regulator with pressure gauge comparison](/hub/grills-and-barbecues/gas-regulator-with-pressure-gauge). Peter F. edits DIY and tools at productscompared.co.uk. We did not measure outlet pressure.

You already have the regulator and the cylinder, and you want to know how to fit a gas regulator without guessing the twist. On UK barbecues the motion depends on the valve.

Our top picks

IGT IGT 4.5 kg butane gauge

Best overall

IGT IGT 4.5 kg butane gauge
8.6/10about £12.49
View offer
Adventure Outdoor Supplies Adventure 21 mm butane clip-on

Alternative

Adventure Outdoor Supplies Adventure 21 mm butane clip-on
8.6/10about £14.95
View offer
Cavagna Cavagna 0.5–2 bar POL

Alternative

Cavagna Cavagna 0.5–2 bar POL
8.0/10about £28.99
View offer
On this page
  1. 1.Identify the valve before you turn anything
  2. 2.POL and the 4.5 kg screw-on
  3. 3.Clip-on heads
  4. 4.Leak test

Identify the valve before you turn anything

Turn the appliance controls off, and leave the cylinder valve closed until the regulator is seated. Look at the metal, not the gauge. Here the 4.5 kg listings are screw-on butane regulators, the 21 mm listing is a clip-on, and Cavagna and Tezla state a POL inlet. If the body is marked in bar or PSI, stop. Do not wind a 0.5 bar regulator down to 37 mbar. The plate check is on the buying guide. A Calor 4.5 kg butane cylinder takes a screw-on. The black washer from the protective cap is not the seal. A 21 mm head is the butane clip on larger cylinders, not patio gas. A 27 mm head clicks on: no spanner, and the gas goes off before you lift it. UK POL is a 5/8 inch left-hand male thread, anti-clockwise to tighten. If the body does not match, do not force it.

POL and the 4.5 kg screw-on

For a POL joint, clean the valve first. UK POL is left-hand, so you tighten anti-clockwise, then nip with a spanner. Clockwise loosens it. Do not wind PTFE tape onto that thread. Point the vent downwards. A 4.5 kg butane screw-on is a different thread, so do not copy the anti-clockwise rule. Follow the direction marked on that regulator. Use the seal supplied with it, not the washer from the black cap. A spanner is only a final nip on a POL nut. Most listings here do not include a hose. Read the date on the rubber. If a regulator has already failed open, replace it. That report is on one 4.5 kg screw-on, not a repair.
IGT IGT 4.5 kg butane gauge

Testsieger

IGT IGT 4.5 kg butane gauge
8.6/10about £12.49
View offer

Clip-on heads

Patio gas uses the 27 mm clip. Push down until it clicks. No spanner, and switch the gas off before you lift it off. No PTFE tape. If it will not click home, the head is the wrong diameter or the valve is damaged. The 21 mm clip-on here is for cylinders such as 7 kg and 15 kg, not the patio head. One review says it did not fit a 13 kg Flogas cylinder. Pushing harder will not fix that. Leak-test before any flame.

Leak test

Brush leak-detection fluid, or a weak soap solution, onto the cylinder joint and the hose joints. Calor and Flogas both forbid a naked flame. Open the cylinder valve with the appliance taps still off, and watch the wet joints. Bubbles mean gas is escaping. Close the valve and do not cook. If bubbles continue after you have cleaned the valve and tightened it the correct way, replace the regulator. Do not add tape or a longer spanner. If you still smell gas, close the valve, leave the appliance unlit, and ventilate. Fixed pipework is a Gas Safe job. A pass is no bubbles and no smell. The dial is not the pass mark. What the needle does with the valve closed is on the contents gauge page.

Common questions

Which way do I turn a POL nut?
Anti-clockwise to tighten. UK POL is a 5/8 inch left-hand male thread. Flogas and Wonkee Donkee both describe that sequence. You then nip with a spanner. Clockwise undoes it. Do not reuse that direction on a 4.5 kg butane screw-on or on a clip-on.
Do I need a spanner for a 27 mm patio regulator?
No. Calor's patio-gas guidance is a push down until the regulator clicks, and no spanner. You switch the gas off before you lift it off. A spanner belongs to the POL nip, not to a 27 mm clip and not to a 21 mm butane clip. If the patio head needs force beyond a firm push, stop. It is the wrong fitting or a damaged valve.
Can I use PTFE tape on the cylinder joint?
No. Do not put PTFE tape on a POL thread or on a clip-on head. Those joints seal on the fitting they were designed with. Tape makes a cross-thread feel finished and makes the leak harder to see. The 4.5 kg screw-on uses its own seal, not the washer from the black protective cap, and not a wrap of tape.
What washer do I use on a 4.5 kg butane cylinder?
Not the washer that comes in the black protective cap. Calor's butane safety sheet says that cap washer is not the seal. Use the seal supplied with the screw-on regulator. Fitting the cap washer can give you a joint that feels tight and still leaks under the soap test. If the proper seal is missing or crushed, replace the regulator rather than substituting the cap washer.
Where should the regulator vent point?
Downwards, not up. Set that before you nip the POL nut. A gauge glass facing you is secondary to the vent. If the only way to see the dial is to point the vent at the sky, the regulator is a poor match for that cylinder.
What if I still smell gas after the soap test?
Close the cylinder valve, do not light the appliance, and ventilate. A soap film with no bubbles plus a lasting smell is still a stop. Replace the regulator or the hose on a barbecue. If the smell is from fixed pipework, use a Gas Safe engineer. Do not treat a failed-open regulator as something to adjust.

Related pages

Butane or propane

Gas regulator with pressure gauge

Best gas regulator with gauge UK for your cylinder

Gas regulator with pressure gauge: match the valve

Gas regulator gauge: how much gas is left in the bottle

Sources

Public UK sources used for this comparison. Listing prices, stars and review counts are the amazon.co.uk figures for these ASINs. Retrieved 22 October 2026.

  1. Liquid Gas UK: Consumer Guidance Sheet 39 (August 2020) (retrieved 22 October 2026)
  2. Calor: which hose and regulator for a gas barbecue (retrieved 22 October 2026)
  3. Calor: gas regulator FAQs (retrieved 22 October 2026)
  4. Calor: 4.5 kg butane cylinder (retrieved 22 October 2026)
  5. Camping and Caravanning Club: gas in caravans and motorhomes (retrieved 22 October 2026)
  6. Flogas: how to connect a propane cylinder (retrieved 22 October 2026)
  7. Gas Safety (Installation and Use) Regulations 1998 (retrieved 22 October 2026)
  8. GOK: does the regulator gauge show the filling level (retrieved 22 October 2026)