Q. Flexible Line With a Water Heater?

Q. Hey Mark, Yesterday someone asked me if they could use “flex line”, like what is used for toilets and under sinks, to connect a gas or electric water heater in his home. What do you think?

Fred O.


A. Hey Fred,

I’m not sure what the code officials would say about it, but it doesn’t seem like a good idea from a practical standpoint. The flex lines under sinks and toilets don’t have a very large diameter. They are only designed to supply a single fixture. The water heater has a much greater volume demand, and the smaller diameter flex line wouldn’t supply the need fast enough. The manufacturer of the water heater probably has installation instructions requiring a ¾ inch supply and service line. Your best bet would be to follow the installation requirements of the water heater itself to the letter. Most manufacturers have those instructions available from their respective web sites if you have misplaced those coming with the unit.

There is a plastic based product, which is somewhat flexible and would probably work as an alternative in this situation. (Assuming your manufacture’s instructions, and local building codes allow it.) The brand name I’m thinking of is called PEX. PEX is a generic term for plastic pipe made from cross-linked polyethylene.

You should be aware that there have been reported problems with certain brass fittings produced by Zurn, which are used to connect the hose sections together. This has lead to a class action lawsuit. Zurn plastic fittings and fittings made by other manufacturers are not part of this case. I would advise any homeowner considering the use of the PEX products to thoroughly research the fitting options available to them.

Anecdotally, I’ve personally found fewer problems with PEX installations than with traditional copper, cast iron, and CPVC plumbing systems. However, because of the problems with the Zurn fittings, I would recommend that anyone who chooses to use such PEX tubing should make sure that all fittings be readily accessible and not hidden where potential leaks could cause harm to your home. To learn more about PEX plumbing, do a web search for “PEX”. For more information about the Zurn fittings, visit http://www.zurnclassaction.com/index.html


3 Responses

  1. They make flexible water connections for water heaters that are larger diameter and meet the code. ASME A112.18.6 is the product standard referenced in the plumbing code.

  2. Bill,

    That’s correct. Thanks for sharing that with the readers. I don’t seen those very often in the St. Louis area, so that option didn’t come to mind.

    I would add that even though they are acceptable to the ASME standards, it would only be appropriate to use them if the water heater manufacturer’s installation instructions approve them as well.

    – Mark

  3. Hey, Mark.

    To the best of my knowledge, every water heater manufacturer approves the metal braid flexible connections as long as they meet local codes, and I don’t know of any local codes anywhere that prohibit them. If they can be used at the toilet and sink, then there should be no problems at the water heater. After all, excepting the water in the actualy water heater tank, the whole house is under the same water pressure.

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