Advice: A few quick plumbing Q's for insight.

[keaton85]

Just picked up a Tartan 4100 hull #007 so a pretty early vintage with old systems.

The freshwater system:
3/8th Grey Poly-B with field terminal style fittings (serviceable)
Two aluminum water tanks and one poly v-berth tank

One aluminum tank was replaced and the original is starting to get the pinholes at the weld, so that has to be addressed.

My plan was to go 1/2 PEX-A with a manifold from tanks to pump with 1/2 trunk and 3/8 drops to fixtures using PEX-A and plastic John Guest push connect fittings. I like using clear PEX due to being able to see water line conditions over time. Thoughts?

Black Water:
I have the normal Y-valve and tank with a vented loop overboard. I have to replace all the Sani-hose due to age/smell. I am considering going just straight to tank and removing the extra hose/complexity of the direct overboard. Almost every boat I've been on is like this. The only downside I can think of is if the macerator goes bad offshore?

[GordMay]

Repairs to PB piping are very difficult, since neither PB plumbing pipe, nor the Quest fittings, used to connect it, are commonly made, or sold anymore.

Thus, you intention to replace, is a good one.

For inaccessible repairs [difficult to access the PB, for removal], the best option is to use a transition coupling [1], designed specifically to transition from polybutylene to PEX pipe.
The PB-to-PEX transition coupling [1] is made of brass, and it compensates for the difference in the inside diameter of PB pipe and PEX. This transition coupling also has two different crimp rings, one that is specifically meant to be used to secure the transition fitting to the PB pipe and one to secure the transition to PEX.
[1] Watts PEX LFP-705 Polybutylene Transition Coupling
➥ https://www.amazon.com/Watts-LFP-705.../dp/B003L1V50Y

[keaton85]

Thanks! I found that sharkbite fittings fit perfectly onto the Poly-B 3/8th which is pretty handy. Not that I like sharkbite all that much.

I can do the whole boat with ease so for cost and bullet-proof installation I might just go all straight PEX-A. I'm trying to stay away from crimp rings and stick with PEX-A or JG puch-connect.

[Jammer]

Welcome. I have a Tartan of similar vintage, though mine is plumbed with the (unusual) polypropylene tubing.


I have had good results with PEX-B and crimp rings. Transition fittings from PEX to PB are readily available at Home Depot, Menards, etc. These use a different crimp ring with the the same crimp tool as the PEX ring,


3/8" is of sufficient size for supply piping -- with the short runs and relatively low output of the pump there isn't a technical reason for anything larger. That said, fitting availability in 3/8" is poor. I found it necessary to use 1/2" for most purposes but have used 3/8" for a few specific runs, particularly for hot water, where it reduces the wasted water from running a tap until the water comes out hot. I did use 1/2" for the suction lines to tanks, replacing the 3/8" that Tartan used.



The push-to-connect fittings, sharkbite, etc., add cost and bulk. Either PEX-A or PEX-B will make for a good installation, but with PEX-A you need an (expensive) expansion tool.


Redoing the whole boat is a big project and may not be necessary if you use transition fittings and leave PB in place where it is in good condition. Usually PB systems fail at the fittings, the tubing lasts a long time.


With most water sources, clear or translucent piping will become opaque over time from scale and rust deposits.


Macerator pumps are notoriously unreliable. They are prone to plugging and jamming under the best of circumstances. If someone aboard flushes a tampon, rag, or wet wipe that will pretty much guarantee that the macerator will jam.

[BAD ORCA]

Originally Posted by keaton85

Thanks! I found that sharkbite fittings fit perfectly onto the Poly-B 3/8th which is pretty handy. Not that I like sharkbite all that much.

I can do the whole boat with ease so for cost and bullet-proof installation I might just go all straight PEX-A. I'm trying to stay away from crimp rings and stick with PEX-A or JG puch-connect.

Same here. I have 1980 3/8 water hose. From your description, Im guessing same exact stuff you have. The sharkbite fitting i have used for several years so far with no issues or leaks yet. Iv'e also used some fittings from McMaster Carr that also have worked perfectly and trouble free.

[keaton85]

Originally Posted by Jammer

The push-to-connect fittings, sharkbite, etc., add cost and bulk. Either PEX-A or PEX-B will make for a good installation, but with PEX-A you need an (expensive) expansion tool.

Thanks, yeah the quick connect fittings were more of the idea of being able to maintain underway, as it will always happen underway at 2am in the worst conditions haha. Yet I think I will just keep a set of quick fittings for repairs.

The PEX-A tool is only $100 and I already have one so that helps! not a fan of the red and blue of PEX-B, as its nice to see whats in the lines.

Definitely a lot harder to find 3/8 fittings, so 1/2 is probably what I will do.

[Scorpius]

I've been using 1/2" PEX with crimp rings for years now. No regrets. I'm not sure about using Sharkbite connectors on suction lines from the tanks. I think they're designed to handle pressure, not suction - and SharkBite fittings are expensive and bulky.

I assume that you will have valves between each water tank and your intake manifold. Otherwise, when one tank runs dry, you'll start sucking air and that will be the end of your water supply.

I'd seriously consider going with a composting/dessicating toilet. Those of us that have them, love them - and they are FAR more reliable and easier and less disgusting to maintain than conventional marine toilets. Plus there's a BIG space saving by eliminating the holding tank.

[GordMay]

PEX stands for cross-linked polyethylene. The letter that follows [A, B, or C] simply signifies the type of manufacturing method, used to cross link the polyethylene, not the grade of PEX.

PEX A is made using the Peroxide, or Engel, method.
PEX A is very flexible, and doesn’t show any coil memory; so, you can repair minor kinks, with a heat gun.
A lower bending radius in PEX-A [6 times the OD vs. 8 times the OD for PEX-B & C] can be useful, in boat plumbing.

PEX B is formed using Silane, or Moisture Cure, method. This is the most common, and [generally] cheapest, PEX pipe type.

PEX C is created using the Electronic Irradiation, or Cold, method of cross-linking.

Since oxygen can promote corrosion and rust to develop, in the ferrous components of a heating system, boilers, radiant floor heating applications, or baseboards usually require PEX tube, with an oxygen barrier, which meets DIN 4726 standard, for oxygen permeability. It is often/usually [?] not approved, for use with potable water, so check.

Material Designation Code:
They all have a Material Designation Code. All PEX pipe is assigned one of these codes, based on their level of chlorine resistance, UV resistance, and hydrostatic design basis (HDB), or pressure rating, as determined in ASTM F876/F877, and SDR9 dimensional standard.
The highest code is PEX 5306.

The first digit is chlorine resistance. The highest rating is a Class 5.

The second digit is UV resistance. The highest rating is a Class 3, which indicates a six-month UV resistance.

The last two digits is the HDB, which is the same for all the PEX tubing sold in the U.S. This will be “06,” indicating a 630 HDB, or a pressure rating of 160 psi at 73 F.

Note: PEX pipe is not approved for continuous UV exposure, so should not be used, or stored, in direct sunlight.