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How to fit a ball valve

Updated: 23 October 2026

You have a threaded water or air valve that already matches the male fitting, and the supply is still live. This page is how to fit a ball valve: isolate, seal the male thread, tighten, and test. It is not a gas-fitting guide. If the pipe carries natural gas or LPG, stop and use a Gas Safe registered engineer. The shelf context is the [ball valve comparison](/hub/diy-supplies/ball-valve). If you are still choosing bore and thread, use the [ball valve buying guide](/hub/diy-supplies/ball-valve/sub/ball-valve-buying-guide) first. If you buy through our links, we may earn a commission at no extra cost to you.

You have a threaded water or air valve that already matches the male fitting, and the supply is still live. This page is how to fit a ball valve: isolate, seal the male thread, tighten, and test.

Our top picks

Bächlein Bächlein 3/4 inch female brass

Best overall

Bächlein Bächlein 3/4 inch female brass
7.5/10about £13.95
View offer
JIVTO JIVTO 1 inch BSP male to female

Alternative

JIVTO JIVTO 1 inch BSP male to female
6.3/10about £15.48
View offer
Bwintech Bwintech 1/4 inch brass pair

Alternative

Bwintech Bwintech 1/4 inch brass pair
5.0/10about £9.99
View offer
On this page
  1. 1.Isolate and drain
  2. 2.Seal the male thread
  3. 3.Open, shut, and test
  4. 4.Stop here
  5. 5.When the joint is finished

Isolate and drain

Turn off the supply that feeds this pipe. On a cold feed that is often the stopcock. On heating, use the zone isolators with the boiler off, and follow the maker's drain-down notes. If a dribble continues, you have not isolated the leg. A valve is not a pipe clip. If you cannot find the isolator, call a plumber. Female-to-female bodies take tape on the nipple. Male ends in this set are the 1 inch JIVTO and the TAILONZ minis. Offer the threads dry. An NPT nipple can start on BSP and then refuse to seal.

Seal the male thread

Wind PTFE on the male thread in the tightening direction. APM's three to five wraps, and Ball Valve UK's two or three layers, are rules of thumb on a taper, not a measured standard. Do not tape a compression olive. Parallel BSP threads often need a washer as well. The Bwintech review is the case: poor included tape, no washers, and a leak until washers were found. TAILONZ tape held one air line at about 70 to 90 psi. Start by hand, then use a spanner on the hexagon without twisting the pipe. Albion's three quarters of a turn past hand-tight is for a compression nut, not these threads.
Bächlein Bächlein 3/4 inch female brass

Testsieger

Bächlein Bächlein 3/4 inch female brass
7.5/10about £13.95
View offer

Open, shut, and test

Handle in line with the pipe is open. Across the pipe is shut. Check a wing handle before you refill, because it is easier to misread than a long lever. A weep at the thread means redo the tape or add the washer. A drip from the outlet while the handle is across the pipe is the ball or the seat. One UK review of the 1 inch JIVTO describes that drip. Leave the valve fully open or fully shut. A part-open ball can damage the seats. On air, charge slowly, and vent the hose before you remake a joint that pops.

Stop here

PTFE will not rescue a slack thread. If the valve rocks on the nipple before any tape, as one buyer found on the standard-port 1/2 inch JIVTO, replace the valve or the nipple. Stop if the pipe is gas. The Gas Safety (Installation and Use) Regulations 1998 require competence, and regulation 9 is the meter control. A title that says for gas does not change that. Stop too if you cannot isolate a shared riser, or if a concealed wholesome-water fitting does not state a dezincification-resistant material.

When the joint is finished

If the dry threads start cleanly, tape the male side, add a washer on a parallel thread, and test with the handle fully open and fully shut. If the female thread is slack before any tape, or the shut valve still passes water, change the valve rather than winding on more tape. If the pipe is gas, or you cannot isolate the leg, stop and call a Gas Safe registered engineer or a plumber.

Common questions

Do I tape the valve or the pipe?
You tape the male thread, in the direction you will tighten it. A female-to-female valve has no male thread, so the tape goes on the nipple. Male minis and the male end of a male-to-female valve take the tape on that end. Do not tape a compression olive. An olive means this is the wrong body.
Which way is open?
With the handle in line with the pipe, a typical ball valve is open. Across the pipe, it is shut. One TAILONZ review describes travel slightly past 90 degrees before the stop, so check the stops. Do not assume a wing handle reads the same way as a long lever at a glance.
Can I leave it half open to reduce flow?
No. A ball valve in this kind of service is an isolator. Leaving it part open can damage the seats, which is the warning in installation notes such as Albion's. If a radiator needs balancing, use the lockshield or the valve the system was designed with. If a tap is too fierce, fix that at a valve meant to throttle, not by parking this lever halfway.
What if the female thread feels loose?
Stop, before tape. A slack fit, as described on the about £8.68 JIVTO against existing 1/2 inch nipples, is a thread problem. PTFE fills a small gap on a taper. It does not turn an oversized female thread into a sound joint. Compare the nipple with another fitting of the same nominal size. If it is loose dry, change the valve or the nipple.
Do I need washers as well as tape?
On a parallel thread, often yes. Tape is the usual seal on a taper. The Bwintech review leaked until washers were added, and the bullets did not promise washers. An air mini sealed with included tape at about 70 to 90 psi is a different joint. Match the joint you have, and test the fill.
When do I stop and call someone?
Call a Gas Safe registered engineer for any gas pipe. Call a plumber if you cannot isolate the leg, if the pipe is shared, or if a hidden mains fitting has no suitable material stated. A drip through a shut valve is a faulty valve, not a cue for more force. Remaking a weeping thread once is normal.

Related pages

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Ball valve for central heating: full bore, open or shut

Sources

Public UK sources and the amazon.co.uk listings compared on this page. Shelf figures captured 19 October 2026.

  1. Water Supply (Water Fittings) Regulations 1999 (retrieved 19.10.2026)
  2. GOV.UK water fittings guidance (retrieved 19.10.2026)
  3. Water Regs UK, Schedule 2 paragraph 3 (retrieved 19.10.2026)
  4. WRAS directory guide (retrieved 19.10.2026)
  5. Gas Safety (Installation and Use) Regulations 1998 (retrieved 19.10.2026)
  6. HSE domestic gas FAQs (retrieved 19.10.2026)
  7. EN 13828:2025 (retrieved 19.10.2026)
  8. Albion Valves ball valve IOM (retrieved 19.10.2026)