Laundry room with a tank-type water heater beside the washer
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Thread sealant on water connections: PTFE tape vs pipe dope, how to apply, and where no sealant belongs (gas goes to a licensed tech)

Tapered pipe threads (NPT) need a sealant to fill the small gaps between threads: PTFE tape, pipe dope (joint compound), or both. Tape is clean and common on small threads (about 1 in and under) and plastic; dope fills coarse or large threads better, but some formulas attack plastic, so read the label. Compression, flare and hose (washer-sealed) connections seal elsewhere and do not get sealant on the threads. Gas piping and gas appliance connectors are licensed gas-tech work: this guide covers water only.

Cross-checked ~15 min easyBrands: All

Before you start

  • Gas: do not make or remake gas joints or connectors; refer to a licensed gas technician. If you smell gas, leave and call the utility from outside.
  • Shut the water and relieve pressure before opening a joint; electric water heaters: breaker off first.

Diagnostic steps

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