PI251216S 1/2in Hose Barb to 3/8in Stem Adaptor

The John Guest PI251216S adaptor joins 1/2in ID hose onto a 3/8in push-fit stem connection, letting you connect flexible hose to a 3/8in tube system such as an RO unit or small-bore pipework. WrekinWater supplies this as a straightforward way to step down from a wider hose bore to the narrower 3/8in stem used across many John Guest fittings. The barbed end is designed to be secured with a hose clip.

When you need this fitting

• You need to connect 1/2in ID hose onto a 3/8in push-fit fitting or tube.
• Your existing stem adaptor has cracked or the hose no longer grips it securely.
• You're stepping a wider hose down to a narrower 3/8in system, such as an RO unit.
• You're replacing a damaged connector found during a service or hose change.

Stepping between two different sizes, 1/2in hose down to a 3/8in stem, only works reliably if each end is matched correctly: the barb needs to be gripped tightly by the hose and clipped, while the stem end needs to push fully home into its mating push-fit fitting. Get either end wrong and you risk a slow weep at the joint rather than an obvious leak, which is easy to miss until it causes damage nearby.

WrekinWater has stocked genuine John Guest fittings for the water treatment systems we sell for over 15 years, working from our base in Bettisfield, Shropshire. Choosing the correct stem-to-barb size from us avoids the trial and error of generic hardware alternatives.

How to fit it

1. Cut the 3/8in tube square and deburr the end if fitting into further push-fit pipework.
2. Push the 3/8in stem end fully home into the mating push-fit connection.
3. Tug-test the stem end to confirm it's seated and gripped.
4. Push the 1/2in hose fully onto the barbed end.
5. Secure the hose with a hose clip.
6. Run water through briefly and check both ends for leaks.