What do you use for an AC raw water manifold?

[q240z]

I'm thinking ahead to the raw water plumbing for the self-contained AC units I'll install in my Chris Craft Roamer refit and am hoping for some suggestions. Since this is an aluminum boat, I'm minimizing copper and bronze inside the boat as much as possible. So even though I've got tons of bronze plumbing bits from previous boats, I want to avoid using it in the Roamer.

My seacocks will be Marelon, as are the tailpieces/hose barbs. But Forespar doesn't make plumbing parts that I can fashion into a manifold to split the raw water supply from 1" to three 5/8" hose barbs. PVC is out of the question (I think) even though the manifold will be above the waterline. I could weld up something out of stainless tube, but if there's something off the shelf, that'd probably be my preference.

Thoughts?

 

[Cricket]

What's wrong with PVC?

Photo is from an 80' Weaver, they are pumping seawater thru the entire boat to individual self contained AC units.

 

[zigzag930]

This is the setup I have onboard Katerina, except only 4 valves. Works perfectly.

The manifold IS above the waterline and has a standard rubber hose from the March TE-7 seawater pump to the manifold.

 

[Pascal]

A $27 stainless steel manifold probably made by the chicoms. What can go wrong with that?

PVC is fine but should be schedule 80. Or you can use nylon or Marelon fittings. Whatever you do do not use brass.

 

[Cricket]

Lots of interesting options with a broad Google search "water manifold plastic" but I like the price of this Home Depot SS one:

https://www.homedepot.com/p/HOME-FL...nless-Steel-FIPT-Manifold-11-100704/204767413

Gives you a spare port and expansion capability, I suppose, after you thread in 5/8 barbs.

DAN

The Home Depot manifold is for natural gas......

 

[cww]

The one from hatteras appears to be bronze and at least in my boat has held up well, what's wrong with yours? Or just redoing the system?

 

[Cricket]

His boat is Aluminum, it's a dissimilar metal issue.

Btw, I had a bronze manifold start to wear thru with pinholes.
All of our stuff is PVC now, some of it is at least 15 years old with no issues.

 

[cww]

His boat is Aluminum, it's a dissimilar metal issue.

Btw, I had a bronze manifold start to wear thru with pinholes.
All of our stuff is PVC now, some of it is at least 15 years old with no issues.

Oh duh, blond moment. Sorry, realized he has a roamer. Those are wonderful boats.

 

[q240z]

Thanks for the input!

1 -- What's wrong with PVC?

Reports of catastrophic failures in marine applications, especially below the waterline, left a bad impression from early in my boating life. This application is high volume but above the waterline, so not as scary. Technical specs indicate that PVC strength drops off dramatically with temperature. Max pressure rating for PVC is at 73°F and it drops quickly from there. At 110°, it drops 50%. 140° is the maximum working temp, by which time the pressure rating is down to 22% of the full rating.

This will be in my ER, so 110° is expected.

It looks like Schedule 80 CPVC is far better, with a max operating temp of 220°F and only 50% strength loss @ 140°F.

2 -- I like the price of this Home Depot SS one

The price is very attractive. And 304 SS isn't a bad choice for materials. That it's made for propane/natural gas applications doesn't bother me, but the spec sheet from Home-Flex says it's max rated for 5psi. I don't know what pressure my AC raw water circuit will be, but that's extremely low...too low for me.

3 -- Or you can use nylon or Marelon fittings

I wish they did, but Forspar says they don't make the components I'd need to make a Marelon manifold.

 

[Bob Quinn]

I don't have experience with plastic on a boat, but I don in my shop.
I have a couple machines that have filter systems that have shut off valves that look just like these.
they are on; I believe, 1.25" diameter pipe. They have never lasted. They work good when new, they a couple years later they lock up and won't turn. When that happens the red plastic handles just snap off. Now granted, these valves are in a dirty water system so it could be the junk in the water that makes them jam up. Just my experience. Don't know what other options there are but some kind of metal might last a lifetime instead of "It worked great until I needed to turn it off in a emergency" Just a thought.

 

[Cricket]

Would glass reinforced polypropylene (Schedule 80) fittings and valves be good in a boat for projects like what we're discussing in this thread?
There are no rating specifics on this website that I can find, but lots of interesting pieces, parts, valves.

https://www.banjovalves.com/

Found these specs at Zoro
BANJO 1" Ball Valve Single Union
Ball Valve, Body Material Polypropylene, Body Style Inline, 3-Piece, Pipe Size 1 in, Connection Type FNPT x FNPT, Full Port,
Max. Pressure 100 psi CWP, Temp. Range -20 Degrees to 150 Degrees F, Ball Material Polypropylene, Seat Material PTFE,
Handle Type Lever, Handle Material Polypropylene, Stem Material Polypropylene, Body Seal Material PTFE/FKM

 

[JD5652]

This is the setup I have onboard Katerina, except only 4 valves. Works perfectly.

The manifold IS above the waterline and has a standard rubber hose from the March TE-7 seawater pump to the manifold.

Same here ....

 

[JD5652]

Thanks for the input!

1 -- What's wrong with PVC?

Reports of catastrophic failures in marine applications, especially below the waterline, left a bad impression from early in my boating life. This application is high volume but above the waterline, so not as scary. Technical specs indicate that PVC strength drops off dramatically with temperature. Max pressure rating for PVC is at 73°F and it drops quickly from there. At 110°, it drops 50%. 140° is the maximum working temp, by which time the pressure rating is down to 22% of the full rating.

This will be in my ER, so 110° is expected.

It looks like Schedule 80 CPVC is far better, with a max operating temp of 220°F and only 50% strength loss @ 140°F.

2 -- I like the price of this Home Depot SS one

The price is very attractive. And 304 SS isn't a bad choice for materials. That it's made for propane/natural gas applications doesn't bother me, but the spec sheet from Home-Flex says it's max rated for 5psi. I don't know what pressure my AC raw water circuit will be, but that's extremely low...too low for me.

3 -- Or you can use nylon or Marelon fittings

I wish they did, but Forspar says they don't make the components I'd need to make a Marelon manifold.

My 1976 58LRC has PVC throughout the boat... primarily in the water systems (including raw water AC) where there is very little pressure. My AC system manifold is above the waterline. However, my bilge piping is also PVC.... but also again very little, if any, pressure.

I've tugged, pulled and twisted on a LOT of the 46-year old PVC piping on my boat without any noticeable concern of reduced strength in the piping or joints... my experience... YMMV...

 

[Captain Ralph]

Nylon, Marlon and sch80 PVC (grey) all make for good manifolds.
I do prefer the screw together Nylon, Marlon. Any issues or needs change; just take it apart and reassemble with fresh Teflon tape.

Lots easier than soldering tubing together.

I'm not sure of 5/8" hose barb to CPVC though.