Can You Use Flex Stainless on Water Heaters? Safety Guide

Yes, flex stainless steel connectors can be used on water heaters for safe and flexible plumbing connections, ensuring durability and resistance to corrosion.

Flexible stainless steel connectors are common in plumbing, but using them on water heaters requires careful consideration. This guide covers when flex stainless works, code requirements, and safer alternatives.

Flex stainless steel for water heater use

Is Flex Stainless Safe for Water Heaters?

Flexible stainless steel connectors can be used on water heaters if they meet three key requirements:

  • Rated for minimum 150 psi working pressure
  • Designed for temperatures up to 180°F
  • Certified to ANSI/NSF 61 for potable water

The International Association of Plumbing and Mechanical Officials (IAPMO) requires connectors to withstand 210°F for residential water heaters.

When Flex Stainless Works Best

These situations allow flex stainless connectors:

Application Recommended Type
Tankless water heater connections Braided 304 stainless with brass fittings
Short runs (under 24″) Corrugated stainless with dielectric unions
Vibration-prone installations Double-braided stainless with vibration loops
Flex stainless for water heater connections

Code Requirements for Water Heater Connections

Most plumbing codes specify:

  1. 18″ minimum rigid pipe before any flexible connection
  2. Dielectric unions required when connecting dissimilar metals
  3. Shutoff valve within 5 feet of water heater

For tankless water heaters with recirculating pumps, some areas require earthquake straps with flexible connections.

Common Code Violations

Avoid these mistakes with flex connectors:

  • Using washing machine hoses (max 125 psi)
  • Oversized connectors that sag and trap sediment
  • Missing temperature/pressure relief valve extension

Better Alternatives to Flex Stainless

For safer installations consider:

1. Semi-Rigid Copper Connectors

Type L copper with proper bends handles vibration better than flex in many cases.

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2. CSST Gas Connectors

For gas water heaters, corrugated stainless steel tubing (CSST) works when properly bonded.

3. Dielectric Unions

Required by code when connecting copper to steel water heater nipples.

Installation Best Practices

Follow these steps for safe flex stainless installation:

  1. Measure exact length needed (no slack)
  2. Support pipes within 18″ of connections
  3. Use two wrenches to prevent twisting
  4. Check for kinks after pressurizing

The International Code Council Evaluation Service maintains a list of approved connectors for plumbing applications.

Maintenance Tips

Inspect flex connectors annually for:

  • Braiding corrosion (white powder or rust)
  • Bulging near fittings
  • Mineral deposits at connection points

Replace any questionable connectors immediately – a failed water heater connection can cause thousands in water damage.

Joye
Joye

I am a mechanical engineer and love doing research on different home and outdoor heating options. When I am not working, I love spending time with my family and friends. I also enjoy blogging about my findings and helping others to find the best heating options for their needs.