Loctite SI 5331 100 ml sealant for plastic threads in plastic cold or hot water installations, NSF P1 approved, sold in packs of 12, price per pack.

Expiration date: 14/04/2026

LOCTITE SI 5331 – Silicone thread sealant for plastic and metal fittings (hot/cold water)

Need a reliable thread sealant for plastic threaded connections used in hot and cold water systems? LOCTITE SI 5331 is a one-component, acetoxy silicone (white paste) that cures with moisture and forms a flexible, low-strength seal—well-suited for plastic fittings, as well as plastic/metal combinations in piping assemblies.

Selection tip: match the product to the thread material, medium, operating temperature and pressure. Similar thread sealing solutions may be available in other listings.

Typical applications

✅ sealing threaded plastic fittings in hot/cold water systems (industry, agriculture)

✅ plastic-to-metal threaded joints in piping and installations

✅ threaded connections in drainage and water handling systems

Why customers choose it

✅ one-component—no mixing, easy to apply

✅ moisture-curing at room temperature

✅ low-strength joint (easier servicing/disassembly) while maintaining sealing performance

✅ suitable for water installations including potable water—when the recommended cure time is respected

How to apply (recommended procedure)

1. Apply the product to the thread (it can be “as manufactured” or wiped with a damp cloth/paper towel).

2. Apply to both the male and female threads and work the product into the threads to ensure good wetting.

3. For potable water systems, allow the sealant to cure for 96 hours at 20–23 °C before commissioning.

Important limitations

✅ Not recommended for use with pure oxygen or oxygen-rich systems.

✅ Do not use in installations exposed to chlorine or other strong oxidizing agents.

Storage

Store in the unopened original container in a dry place. Recommended storage temperature: +8 °C to +21 °C. Storage below +8 °C or above +28 °C may adversely (and irreversibly) affect product properties. Do not return dispensed material back into the original container (risk of contamination).

FAQ – common customer questions

Is LOCTITE SI 5331 suitable for plastic threads? Yes. It is designed for sealing threaded joints in plastic and for plastic/metal combinations in hot and cold water systems.

When can I put potable water into the system? For potable water applications, allow 96 hours curing at 20–23 °C before commissioning.

Can the joint be disassembled later? The product forms a low-strength seal, which typically supports service disassembly while maintaining sealing performance when applied correctly.

Is it suitable for oxygen or chlorinated systems? No. It is not recommended for pure oxygen/oxygen-rich environments or for installations with chlorine or other strong oxidizers.

How do I know the application is correct? Apply to both male and female threads and work it into the threads to achieve continuous wetting/coverage.