Thread Sealant & PTFE Tape

70 items: 33 pipe thread sealants, 15 PTFE tapes, 9 caulks, 5 plumber's putties, 3 duct tapes and 5 specialty sealants, from RectorSeal, Mill Rose, Hercules, J.C. Whitlam, Loctite, Chatham Brass, Pasco, Harvey, IPS and OmegaFlex.

PTFE tape and Teflon tape are the same product — Teflon is a trademark and PTFE is the film itself, so the two names on two shelves are one thing. What is not interchangeable is the colour. Mill Rose codes the roll by service and the name on the package is the spec: red for water, yellow for gas, green for oxygen, plus dedicated stainless steel, Copper Guard and Nickel Guard rolls. Gas-rated tape is a heavier, denser film than general-purpose white and it is what fuel gas work calls for — grabbing the thin white roll off the truck for a gas thread is the substitution inspectors look for. Green oxygen tape is manufactured oil-free, because oil in an oxygen line under pressure is an ignition source, not a mess.

Tape and dope do different jobs, which is why the trade often uses both. Tape fills the thread and lets the joint turn further before it tightens. Pipe dope lubricates the threads going together, fills what the tape misses, and stays workable so the joint can be broken later. On gas and on larger diameters the common practice is tape first, dope over it — belt and suspenders on a joint nobody wants to revisit.

Neither one goes on a compression, flare or union joint. Ever. Thread sealant is for tapered NPT threads, where the seal comes from metal wedging into metal. A compression fitting seals on the ferrule, a flare seals on the flare face, and a ground-joint union seals on its machined seat — the threads on all three only supply clamping force. Tape on those threads does nothing useful and can hold the joint apart just enough to leak. This is the single most common misuse of both products.

Thread sealants split into three behaviours and the label says which. RectorSeal's line makes it explicit: T Plus 2 and Blue+ are non-hardening and PTFE enriched, so the joint comes apart years later; No.5 is soft setting and slow drying, the traditional choice where the joint is meant to stay put; Tru-Blu is fast-dry and PTFE enriched, for when the system gets pressure-tested the same day. Hercules covers the same ground with Pro Dope, Real Tuff, Megaloc and Grrip, and Mill Rose's Blue Monster runs from a 2 oz tube to a 16 oz brush-top. Match the behaviour to whether anyone will ever need to open that joint again.

Plumber's putty is not a pressure sealant. It beds a sink strainer, a pop-up flange or a drain body against the fixture, where nothing is pushing on it, and it stays soft forever so the part can be pulled. It does not belong on a threaded pressure joint. Standard Sta Put covers the ordinary case; Sta Put Ultra is the version stocked for surfaces where the standard putty would stain, which on stone or some plastics it will.

Checking materials before you pick: PTFE tape and PTFE-enriched dope are compatible with potable water, gas and most plastics, but a few plastic threads are attacked by solvents in some hardening compounds — on plastic, a non-hardening PTFE product is the safe default. The nickel-based anti-seize here is for threads that will be taken apart hot, not for sealing.

Sealants sit alongside pipe fittings, black iron fittings, gas press fittings, solder and soldering and installation tools.