PEX usage in marine applications

May 20, 2016
3,014
Catalina 36 MK1 94 Everett, WA
One project on my to do list is to put in a salt water wash down pump. I would "T" into the head supply line and use reinforced PVC to the pump (mounted above the waterline) - but on the output can I use 1/2" PEX to run to the anchor locker in the bow and someplace in the stern?? The pump would only be turned on when actively used.

If so is crimp, expansion, press, or push (shark bite) the preferred method

Thanks

Les
 
Oct 22, 2014
20,993
CAL 35 Cruiser #21 moored EVERETT WA
Les, examining new boats it appears that PEX has become a preferred resource for fresh water systems. I would guess that with a proper thru hull valve system it might serve. There is something about a double clamped hose on a thru hull fitting that makes me feel a bit safer. What do you do to handle the water in the system during the winter? Leads me to consider the wash down hose as a totally separate system where the access to water is a hose I drop in the water while I want to do the wash down and then coil and stow the intake hose till needed again. The wiring, pump and hoses could be located in a locker and the hoses dropped over the side and taken to where needed when in use.
 
Feb 20, 2011
7,990
Island Packet 35 Tucson, AZ/San Carlos, MX
Pex is great stuff, but just know that its UV resistance is poor.
 
Oct 26, 2008
6,045
Catalina 320 Barnegat, NJ
I sure hope PEX is suitable, and the sharkbite connections, too! I just finished plumbing the whole boat with it for a pressure system. My nightmare is that I'll have water spraying out at every fitting when I pressurize it for the first time this spring!
 
Jul 7, 2004
8,402
Hunter 30T Cheney, KS
I've used pex in the home for some years now. Both crimp and Sharkbite connections. The one down side to pex is it doesn't bend much, meaning more joints in tight places. They warn against exposure to UV but that shouldn't be a problem in proper applications.
 
Jan 22, 2008
1,654
Hunter 34 Alameda CA
Will the materials used in the fittings stand up to long term standing saltwater exposure? Even though you only plan on using PEX and its associated fittings on the output of the pump, typical brass for home use may not last very long. Also as justsomeguy says, the UV resistance is poor. For home construction, there are limits as to how long PEX can be exposed to sunlight before it has been installed in or under a building (30-60 days). Longer than that and it has to be discarded.
 
May 24, 2004
7,129
CC 30 South Florida
Give it a try, if it starts leaking after some hours of hull flexing then go back to hoses and clamps.
 
Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
When I put in a washdown pump on my B323, I was pre-advised to use the biggest thru-hull and hose to supply as much water to the sprayer as the pump could move. I used 3/4, and sometimes that does not seem like enough pressure.
 
Apr 4, 2016
201
Newport 28 Richardson Marina
PEX is great stuff, I have installed hundreds of thousands of feet of it in radiant heating applications. For plumbing your domestic water system I think it is great, I prefer the hose clamp connection which uses the special ratcheting pliers for crimping. For a saltwater wash down application I do not feel the brass domestic plumbing fittings will hold up very long. Some commercial only suppliers like Wirsbo make plastic fittings and you use a ring of PEX to make the connection, all plastic, I would trust it on the downstream side of a sea-cock. The tools for the latter application are a couple hundred bucks though and unless you have a friend who is a plumber it gets cost prohibitive. Flexible PVC pipe which you can glue up cheaply may be a better option, you can find pretty easily.
 
Nov 30, 2015
217
MacGregor 26S Lakehills, Tx
I may be a bit odd here, but I ran PEX tubing up the interior of my mast to keep the electrical wiring and antenna wire from banging around. The wiring is inside the tubing.
 
May 6, 2010
472
1984 Oday 39 79 Milwaukee
I replumbed the domestic water on our 34 several years ago with Pex, using a fitting similar to a Shark Bite. I have had no problems at all with the plumbing or fittings, but we are in fresh water. I think the fittings I used were by Watts, they do not seem to have as much metal as the Shark Bites, in fact they may be all plastic.
 
Dec 25, 2000
5,702
Hunter Passage 42 Shelter Bay, WA
Hunter used 1/2 inch Zurn (Quest) Pex Quicktite brand polybutylene grey plastic hose for the fresh water system on our 1991 P42. It has worked well for us over the years and was trouble free. It is also very reliable when installed correctly. It is my understanding that Hunter uses a different product on newer model boats.

Except for an improperly installed fitting that failed, the product has held up well and should be suitable for what you want. As mentioned in other posts, and if it were my boat, anything below the waterline should be double clamped using duty rated reinforced hose before connecting to the above the waterline PEX product.
 
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May 20, 2016
3,014
Catalina 36 MK1 94 Everett, WA
Thanks all. I'll be using reinforced pvc to the pump and pecks on the output side.

Terry missed seeing you Wednesday at the skippers meeting.
 
Dec 25, 2000
5,702
Hunter Passage 42 Shelter Bay, WA
Thanks all. I'll be using reinforced pvc to the pump and pecks on the output side.

Terry missed seeing you Wednesday at the skippers meeting.
Thought about y'all, but it was Ash Wednesday. Plan on attending this week.
 
Sep 30, 2016
339
Island Packet IP 44 Ventura, CA
I have experience with PEX in residential applications. Its great stuff and very convenient compared to copper. As for the sharkbite slip-on fittings: my only caution for these is they seal with a rubber O-ring on each end. And rubber o-rings get old and brittle over time. I would use the crimp fittings over sharkbite fittings if a "permanent" repair is being done.
 
Jun 9, 2004
615
Catalina 385 Marquette. Mi
Pex is in our C-385. WM has the tube and fitting, although Catalina used metric, which WM had. Its great....especially for bypassing the hot water heater here in the great white north.
 
Jan 18, 2016
782
Catalina 387 Dana Point
I'd use nothing other than PEX for water lines in a boat, house, or RV. (Unless it's exposed to sunlight) It is far superior to everything else.

For fittings, by far the very best is the Uponor/Wisbro ProPex system. Fittings are inexpensive. The magic tool is very expensive. Not too hard to use in tight locations. The fittings are available in plastic, so corrosion would be a non-issue. Has to use PEX-A tubing (not typically available at home depot).

The crimp type fittings are decent, but you have to be careful to get them crimped perfectly - i.e. use the "tester" measurement tool. Hard to crimp in tight locations.

Slip-on fittings like Sharkbites are ok. I wouldn't put em behind drywall, but they're OK for a boat. There are some plastic ones made - I'd use the plastic ones. (Hopkins-Carter sells em, bet you can find lots of vendors)

There are radius supports for tight bends - you rarely will need an elbow.

Video about how ProPex is used: