Replacing ALL of the plumbing

Feb 19, 2008
508
Catalina 320 Tawas Bay Yacht Club
Hey everyone - Thanks for the advice.
I'm oddly intimidated by starting new boat projects, but I can usually figure them out as I go along. I think I'm going to bite this off in the spring.

My first land based plumbing project was replacing ALL of the galvanized pipes in my first house with copper. Literally a friend showed me how to sweat copper on Saturday and on Monday I started cutting the pipes out. I only had to knock down ONE beautiful 70 year old plaster wall (I think your first house should always be a small one).

BTW my wife made me promise it would be done by Easter, and it was . . . I caught her on a technicality, she didn't specify what year!
 
Dec 2, 1997
9,011
- - LIttle Rock
When you say "ALL" the plumbing, are you including the sanitation plumbing or limiting this project to the fresh water system? If you're including the sanitation system, I'll be glad to help you.

--Peggie
 
Sep 28, 2025
87
Catalina C 30 MK1 1983 Stockton Lake Missouri
I have been replacing my hose and fittings with the same as was there before. Worked for 40 years as it was.
 
Aug 17, 2010
364
Oday 35 Barrington / Warwick RI
I posted this in the O'day Bigger Boats sub-forum yesterday, and somebody pointed me here.

I just bought 100' each of red and blue PEX-A, an assortment of fittings, and a
PEX-A expansion tool, so that I can replace all of the 40 year old Polybutylene (PB) pipe in my 1986 O'day 35. The PB pipe is grey.

I have had a couple of small leaks over the 15 years that I have owned the boat, but I still recall the broker recommending that I replace all of the pipe when I bought the boat.

Google Gemini says this:

"
For marine water systems, PEX-A is generally considered the best choice, followed by PEX-B, while PB (Polybutylene) should be strictly avoided due to reliability issues and bans in many regions. [1, 2, 3]
Here is how they compare for boat installations:
  • PEX-A: The top choice for marine plumbing. It is highly flexible, making it incredibly easy to route through tight, twisting bilge spaces and bulkheads. It utilizes expansion fittings, which maintain the full interior diameter of the pipe and ensure maximum water flow to your fixtures. It also boasts excellent freeze-resistance. The main drawback is that it requires an expensive expansion tool. [1, 2, 3, 4, 5]
  • PEX-B: A stiffer, slightly more rigid pipe. While functional, the insert-style fittings have a smaller inner diameter, which creates flow restrictions and can reduce water pressure in your boat's system. It cannot be expanded, and if it kinks, the damaged section must be cut out. However, it is cheaper and uses standard crimp or clamp tools. [1, 2, 3, 4]
  • PB (Polybutylene): Obsolete and notoriously prone to leaking and degradation when exposed to chlorine over time. You should not use PB for a new installation or repair. [1, 2, 3, 4, 5]
"
My question is whether anyone here has done this? If so, how long did it take and there any tips that you can share?

Here are some pictures of what I'm dealing with;
20260608_115848.jpg

The blue pipe is a 15mm add on under the lavatory that provides fresh water to the Vacuflush head.
20260608_120234.jpg

Under the galley sink. Two "T"s the branch of each T goes to the hot water heater.
20260608_120709.jpg

This is the hot water heater in the lazerette. Looks like I have to fix the strain relief on the AC for the hot water heater.
20260608_120713.jpg

Another view of the HW heater. This is the bypass that really doesn't work well for winterizing. I plan to get rid of it.

20260608_115634.jpg
20260608_115643.jpg

These two pictures are under the port settee, where the accumulator is mounted. The grey thing is a spare wheel pilot.
 

Apex

.
Jun 19, 2013
1,223
C&C 30 Elk Rapids
I replaced with PexB. getting to the tanks was the most difficult, access is always hard. Couple of learnings is my manifold was too short, so handles would collide...Easy fix someday. Add in drainage service points for winterization. I removed all floor boards and the installation really looked tidy.
 
Aug 17, 2010
364
Oday 35 Barrington / Warwick RI
Note; I looked into getting push-to-connect fittings, but read (somewhere) that they are prone to leakage from the vibration that one may experience on a boat. Now, I'm not always slamming through chop, but entering Buzzards Bay from the Canal is frequently "sporty." I would prefer to minimize the possibility of having to chase down water in the bilge after exiting the Cape Cod Canal. You may note that my last picture (above) clearly shows a SharkBite fitting (and the logo). Look closely, and you will see verdigris from a small, occasional, leak.
 
Nov 6, 2020
569
Mariner 36 California
Note; I looked into getting push-to-connect fittings, but read (somewhere) that they are prone to leakage from the vibration that one may experience on a boat. Now, I'm not always slamming through chop, but entering Buzzards Bay from the Canal is frequently "sporty." I would prefer to minimize the possibility of having to chase down water in the bilge after exiting the Cape Cod Canal. You may note that my last picture (above) clearly shows a SharkBite fitting (and the logo). Look closely, and you will see verdigris from a small, occasional, leak.
I think the trick to not having them leak is to not put any stress at all on the hose where it goes into the fitting. Not that thats an absolute guarantee, and not that it matters since you are doing PEX-A. I just redid all of mine with PEX-B push to connect fittings and paid close attention to this. No leaks at all. The only leaks I did have where fittings that I did not push in all the way and get them to seat properly past the O-ring. Its been a couple of months and all is good. Luckily mina are all easily accessible if I do need to change one out. I agree though PEX-A would be much better if you have the time.
 
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