Recurring issues on recreational vessels Part 2

Residential plumbing on a boat and why you should avoid it.
 
For part two of our series on recurring issues on a boat we will look at the potable water plumbing system.  Most boats will have some combination of flexible hose and flexible tubing.  The flexible tubing is most often PEX A or PEX B on vessels.  This can come in several colors, usually red for hot potable water, blue for cold potable water and a teal for watermaker water that is filling the potable water tanks.  Today we will discuss some of the pitfalls of going to your local home improvement store to pick up parts for your vessels plumbing system.

The ABYC Standard H-23 governs the potable water system on vessels.  While most of these standards are the same for residential plumbing as they are in the marine industry the most frequent issue you will come across if you repair a plumbing issue with home improvement parts is the size.  If you walk into any home improvement store looking for PEX that may fit your vessel you will see sizes of ½” and ¾” for tubing, fittings, valves, etc.  However if you were to purchase a similar fitting or tube from a marine supply store like Marine Craft Supply, Defender, or West Marine you will notice something different.  The vast majority of options will be 15mm and not ½” or ¾”.  Whale products will have reducers or other fittings to work to the sizes that are odd to marine use such as ½” or ¾” but the standard is 15mm.  When you bring your new fittings from the home improvement store and install them on your vessel they may even appear to fit given the sizes are so similar.  However, if they do not leak immediately when you install them they will leak soon.  Always ensure you are using the correct sized fittings for your potable water system.
 
If you want the ease of use of something like a Shark Bite fitting, Whale makes quick connect fittings that require no special tools.  These fittings can be uninstalled and reinstalled several times in case you didn’t cut your PEX tubing perfectly to size the first time.  You will see these fittings all over most modern vessels due to their ease of installation and lifespan in the marine environment.  The Shark Bite fittings also may not be corrosion resistant in the marine environment.
 
Another way to secure PEX fittings is to utilize Oetiker clamps and fittings.  These fittings make a strong connection but they do require special tools to install and remove.  Most boat owners do not have these in every tool kit.  If you prefer this connection the tools are fairly inexpensive and easy to use.
 
Whichever route you go to repair your vessels potable water system the first step and the most easily overlooked one is selecting the correct size.  It may be hard to discern 15mm or ½” simply by looking at the tube.  If you’re unsure grab some calipers and confirm before you make a run to the store. 

Some of the ABYC standards we discussed here are;
H23.6.2 Metals and metal alloys shall be corrosion resistant, or coated to provide protection from corrosion, and mated parts shall be galvanically compatible.

H23.6.5Joining  compounds  in  potable water systems  shall  comply  with  the  requirements  for  materials  as  stated  inH-23.6.3.
 
If you are looking for repairs to your marine plumbing systems let us know at Marine Craft and we can help ensure you keep the potable water in and the sea water out.  You can also view our YouTube video for this subject here.

​We'll see you out on the water.
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Frequently Asked Questions

Can I use residential plumbing parts like PEX and fittings on my boat?

No — you should never use residential-grade PEX, fittings, or connections (e.g., SharkBite from home improvement stores) on a vessel. Marine environments require marine-grade, tinned, corrosion-resistant components. Residential parts often fail quickly due to vibration, saltwater exposure, and size mismatches (½" vs. standard 15 mm marine PEX).

What size PEX tubing should I use on a boat?

Always use marine-standard 15 mm PEX tubing (not ½" or ¾" residential sizes). Brands like Whale, John Guest, or similar marine suppliers provide the correct fittings. Using the wrong size leads to leaks — even if it seems to fit initially. Use calipers to confirm sizing before buying.

Are SharkBite-style push fittings safe for boats?

Only marine-grade versions (e.g., Whale Quick Connect fittings) are safe and recommended. Standard residential SharkBite fittings are not corrosion-resistant in saltwater and can fail under vibration. Whale fittings allow easy install/removal without special tools and are built for marine use.

Can I use Oetiker clamps for boat plumbing?

Yes — Oetiker clamps and fittings create very strong, reliable connections when installed correctly. They require a special crimping tool, but the tools are inexpensive and widely available. They’re a preferred option for many marine professionals.

What does ABYC say about potable water systems on boats?

ABYC Standard H-23 governs potable water systems. Key rules include using corrosion-resistant metals/alloys (H-23.6.2), galvanic compatibility, and joining compounds that meet H-23.6.3 requirements. Residential parts rarely comply, increasing leak and contamination risks.

Where can I get the right marine plumbing parts and service?

Shop at marine suppliers like Marine Craft Supply (www.marinecraftsupply.com) for correct 15 mm PEX, Whale fittings, Oetiker clamps, and more. For professional installation or repairs, contact Marine Craft NC at 252-571-9980 — we specialize in ABYC-compliant potable water systems so you keep fresh water in and seawater out.

Posted by Dave C., ABYC Master Technician 08 March 2026