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Old 07-06-2022, 11:14 AM   #1
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Why not pex everywhere?

My 2001 Mainship 390 has pex tubing, but from the factory came with the compression-screw on fittings that are all being replaced as I come across them with crimped connectors or shark-bite style if Iím unable to crimp something. As Iíve been doing this and staring at other various hoses Iíve been wondering, why not pex tubing and connectors more places?

Iím not advocating replacing anything like through hull water intake hose, Iíll stick with the marine water hardwall hose for that stuff.

What about all the super cheap corrugated type bilge discharge hose? They used the same stuff on most sink and any other type of drain I come across.

I also noticed my supply connections for the A/C-heat units are cheaper hose. I know most will say not skimp there and I agree, but Iíve thought about it.

Some places may be more challenging with bends and turns, and Iím not fond of adding connectors in any spot I canít easily monitor. Iíve heard there is something called ďflexi-pexĒ that may handle bends better.

Iíd be curious about your thoughts on this. Thank you!
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Old 07-06-2022, 11:54 AM   #2
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I think flexibility is a big factor, especially as you get into large hose/pipe sizes. Marine hoses can bend and hold a curve without kinking, where PEX has very limited ability to do that. So you end up adding elbows to PEX which reduces flow. Also PEX is a bit smaller ID vs hose. And I wouldnít want to use any fittings that contain steel or brass with salt water.

Another consideration are the various hose ratings that marine hose has. I donít know what the specs are behind those ratings, and whether PEX meets them. Thatís regardless of whether they have been certified.
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Old 07-06-2022, 11:56 AM   #3
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I'm not sure if the 'flex pex' that you mention is the rounded ( in a coil). I will post pics, and I mentioned in an earlier post that I had a leak of the old polybutylene hose originally installed on my boat. I replaced all lines with pex, using a combination of straight pieces when it was appropriate and the coiled when needed. I alreadly had a compression tool, so all my fittings are compression fittings and of course they are all where I can get to them.
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Old 07-06-2022, 12:17 PM   #4
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Pex sizes correspond to copper tubing sizes. Things like bilge pump hoses
and other drain hoses will not be easy to replace with Pex without changing the fittings.
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Old 07-06-2022, 12:24 PM   #5
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Get rid of the corrugated hose, particularly in bilge pump discharge application. But just use quality smooth wall hose.

I re-plumbed most of my water system in PEX though.
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Old 07-06-2022, 12:42 PM   #6
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Quote:
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Get rid of the corrugated hose, particularly in bilge pump discharge application. But just use quality smooth wall hose.

I re-plumbed most of my water system in PEX though.
Right. The only advantages of corrugated stuff is it's cheap and easier to route due to it's flexibility. The corrugations slow the water flow which you do not want to do for a bilge pump. The smooth walled vinyl hose with the braid inside (from the hardware store) would better and about the same cost or just a little bit higher.
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Old 07-06-2022, 12:44 PM   #7
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I like PEX for plumbing but not for discharge hoses. I use SaniFlex hose for discharge if the size works, smooth bore and very flexible. For making 90 degree turns in PEX I use hose benders found in plumbing supply stores. It makes a 90 without kinking the tube and no fittings to leak or restrict flow.
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Old 07-06-2022, 01:20 PM   #8
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And I wouldnít want to use any fittings that contain steel or brass with saltwater.

Great point on the saltwater. Not an issue currently but probably will be someday.
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Old 07-06-2022, 01:26 PM   #9
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Why not pex everywhere?

Kind of on the same subject, my boat has no p-traps on any of the drains. Just the undesirable bilge hose running straight out as a drain. Some of the bends are collapsing and itís just a matter of time before clogs or leaks happen.

Has anyone added p-traps? I think Iíll be mating any trap I put in with hose just because of access issues but adding traps seems like a good idea. Or is there a reason traps arenít used on boats?

Thanks
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Old 07-06-2022, 01:32 PM   #10
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I don't use P traps on boat sink and shower drains. It is my understanding that P traps in house plumbing are to create a seal so that sewer gas does not back up into the house.

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Old 07-06-2022, 01:33 PM   #11
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As Portage_Bay mentioned, the trap in a house drain is to block sewer gas from coming back up the drain. No such problem on a boat where the drain goes right over the side, so no reason to have a trap. And no traps means the drains are harder to clog as well.
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Old 07-06-2022, 01:35 PM   #12
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Quote:
Originally Posted by Portage_Bay View Post
I don't use P traps on boat sink and shower drains. It is my understanding that P traps in house plumbing are to create a seal so that sewer gas does not back up into the house.

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That is correct. No advantage in a boat, and if you winter in a cold climate they're one more thing to winterize. I'm from Michigan so that's something I pay attention to.
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Old 07-06-2022, 01:49 PM   #13
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Just have them drain straight out, no P traps needed or desired. You can use spa type hose for these non critical applications. Smooth bore but not quite as flexible.
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Old 07-06-2022, 02:00 PM   #14
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Pex-A is more bendable and kinks can be repaired with a heat gun. I think the black plastic 90* bend on the blue tube on the righthand side of the photo below is what Comodave is refering to.

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Old 07-06-2022, 02:37 PM   #15
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Great points after I thought about what PTraps are for I had the same thought.

Just had to think a little harder!
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Old 07-06-2022, 02:38 PM   #16
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Quote:
Originally Posted by Datenight View Post
Pex-A is more bendable and kinks can be repaired with a heat gun. I think the black plastic 90* bend on the blue tube on the righthand side of the photo below is what Comodave is refering to.



Rob

Cool. I used a couple of those on the head faucet replacement. I thought it was the right thing, confirmed!
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Old 07-06-2022, 02:56 PM   #17
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Quote:
Originally Posted by Datenight View Post
Pex-A is more bendable and kinks can be repaired with a heat gun. I think the black plastic 90* bend on the blue tube on the righthand side of the photo below is what Comodave is refering to.

Rob
Exactly.
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Old 07-06-2022, 04:02 PM   #18
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I recently replace all of my hot water lines with pex. It fixed all my hot water leak issues. I also bought blue for cold. The job was so hard to complete on my 55 I said hell no to the cold, not unless I have to. Three or four times I thought it was going to be impossible to complete just the hot but we got it done. Scary moments after cutting lines then not being able to proceed. Many obstacles but we got it done. No more leaks for months now.
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Old 07-06-2022, 04:52 PM   #19
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On a previous 46í I replumbed the whole boat. It was a big job. I think I used SeaTech fittings and tubing. I ordered 10í sticks so they were straight. The straight pieces were much easier to work with than the rolled tubing. The rolled tubing really wouldnít straighten out well and wouldnít go straight in hidden areas, instead it would just curl up and not go on through.
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Old 07-06-2022, 05:29 PM   #20
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I too did my whole boat but with the crimp stainless rings as suggested by Rick B.

I ordered the more flexible pex and it came in a roll...but a snap to straighten and feed with care though dead areas or rebend into tight 90's with the 90 degree curved supports. Super to work with and also nice to feed a continuous length and cut where a branch was necessary.

The stainless ring crimps are easy to install one handed when you have to reach into a hard to reach area,,, not one leak to start with or for many years.

To me it was one of the easiest jobs on the boat....maybe because I rearranged just about everything in the engine roon to make installs and repairs easier.
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