Common Rail HVAC Piping

[racclarkson@gmail.com]

Been wanting to get rid of what could be OEM black rubber hoses feeding and draining my four Cruisair HVAC's. Started pulling and kinda got into it. This is just some of the junk I pulled out.

I also junked my PCV feed manifold in favor of running 1" PVC pipe and tapping into the feed water at the individual units.

Hate to show the two older units, but awful proud they're still percolating at 37 years old!

So after addressing the feeder side, I ran a 1" PVC pipe behind the top rack and picked up the discharges along the way aft. While I was at it, I installed two ports for future descaling and a valve to close the discharge loop; the seacock will serve to close the intake portion of the loop. The brass plug is a temp.

Then the pipe goes to the ER rear bulkhead with a bit of fall where it picks up a hose to the transom discharge. Probably will replace that hose run with pipe and just use a foot or so of hose at the thru hull.

It sure looks a lot nicer, and I picked up some valuable wall space by getting rid of the old spaghetti. I rate the job a B+. That's the flavor blood I left all over the place. Hatt's ain't for hemophiliacs!

 

[SEVEN]

Very lean Robert. If you ever visit California please plan on staying an extra month so you can update each motor room. Beautiful job.

 

[SKYCHENEY]

I'm not sure I would use PVC for a raw water line, especially if it was below the waterline. It seems too brittle for that. I'm thinking hose or even PEX, but not PVC. I hope that works out okay. But I'm not a surveyor so I have no idea if that's acceptable.

 

[Cricket]

All of our water cooled AC's, refrigeration and bait wells have PVC piping and manifolds similar to Robert's which recently went through at least their 2nd survey without issue.
What you can't do is attach the PVC directly to a thu hull, need flexible hose for those connections. On the supply side there's a pump and hoses between the thru hull and the manifolds.
We did use Marelon and or fiberglass tubing for any engine items, including where all the discharges hook into the exhaust tubes at the transom.
Essentially copied what we saw on some custom boats and Vikings, etc.
Everything is sch 40 or sch 80 pvc, it doesn't seem to make sense that the glue joints are stronger than the threaded ones but they are.

Robert, we added valves for every inlet and discharge to be able to isolate a unit if we have to.
One of our projects this winter is to add extra ports to make it easier to run Barnacle buster thru.
Also adding piping and valves to connect port and stbd systems together to be able to use water from our Eskimo water pump which is more in the center.
Pump is big enough to handle either the port or stbd loads, along with the Eskimo, if 1 of those pumps fail.
.

 

[racclarkson@gmail.com]

Good info, thanks. And all my piping is above the waterline fed by hose from pump. I’ve isolated a unit before and just plugged the lines. Not much room for valving on mine. Also, the barbs are schedule 80. A couple of years back I replaced the sagging cockpit drain hoses with PVC-improvement.

 

[jim rosenthal]

I recall seeing convertibles a few years back with the AC seawater discharge inside one of the main exhausts- much quieter than mine which go out the side. Is that where you ran it to?

 

[racclarkson@gmail.com]

I recall seeing convertibles a few years back with the AC seawater discharge inside one of the main exhausts- much quieter than mine which go out the side. Is that where you ran it to?

Not good options for tapping into the exhaust. You're right, it is a quieter way to go. On the other hand, I get extra giddy up from my water jet.

 

[Cricket]

We used Marelon 90 degree fittings to tap into the exhaust tubes. Epoxied a 90 into a Marelon thruhull, epoxied that into the exhaust tube with the nut on the top of the tube and then used female 90s on the inside to attach the hose from the PVC pipe running from the manifolds or equipment in the ER.
You can't dump drain lines, gutter drains, baitwell drains into the exhaust because fumes will/could exit at the other end if there's no water flow. Built a manifold centered on the inside of the transom to handle all of those drains, has a long oval hole covered with half a tube so water doesn't come in while in reverse.

 

[racclarkson@gmail.com]

Turns out there are good options to tap into the exhaust. I’ll put that on the next owner’s todo list.

 

[Wiredup62]

We used Marelon 90 degree fittings to tap into the exhaust tubes. Epoxied a 90 into a Marelon thruhull, epoxied that into the exhaust tube with the nut on the top of the tube and then used female 90s on the inside to attach the hose from the PVC pipe running from the manifolds or equipment in the ER.
You can't dump drain lines, gutter drains, baitwell drains into the exhaust because fumes will/could exit at the other end if there's no water flow. Built a manifold centered on the inside of the transom to handle all of those drains, has a long oval hole covered with half a tube so water doesn't come in while in reverse.

Are you able to show photos of the manifolds and the attachments at each unit for the shutoff valves? I would like to work on cleaning up my water discharge lines, and add some quick connects for barnacle buster.

 

[jim rosenthal]

The boat I saw with the AC seawater discharge coming out the exhaust- they had epoxied a molder fiberglass tube into the upper part of the larger exhaust barrel. One of the great things about convertibles is that if you d/c hte genset cooling seawater or the AC seawater on the transom, you don't hear it inside the boat. Really I should reroute my genset exhaust to the back of my boat, but there's already a through hull in the side of it. And it's noisy.

 

[Cricket]

Wiredup, thought I had some pix on my phone but don't.
Not sure when I will be back at the boat, the colder it gets the less likely since it's wrapped up and stored.
Check out the manifolds on Weaver Boatworks website.
There's other pix in some of their other builds too.

https://www.weaverboatworks.com/escapade-80/

 

[racclarkson@gmail.com]

Nothing like a new build! Just a comment on valving HVAC systems. Unless each system has its own thru hull discharge, you’ll need two valves per unit. Units using a common discharge line will backfill each other when a single intake valve remains open. Since the need to isolate, in my experience, is rare, a couple of pvc plugs make sense unless you have the space.

 

[rsmith]

I'm not sure I would use PVC for a raw water line, especially if it was below the waterline. It seems too brittle for that. I'm thinking hose or even PEX, but not PVC. I hope that works out okay. But I'm not a surveyor so I have no idea if that's acceptable.

Not just that when it gets hot it gets soft and fails. When I rebuild my house after the 04 hurricanes I capped the copper stub outs with PVC for the plumbing inspection. Inspector told me don’t use them they crack and blow off. I rounded up every brass and steel cap I could find. I was short one. During the night it cracked and blew off. Flooding out the house. I’d never use PVC for anything. Especially in the hostile confines of an engine room.

 

[racclarkson@gmail.com]

Not just that when it gets hot it gets soft and fails. When I rebuild my house after the 04 hurricanes I capped the copper stub outs with PVC for the plumbing inspection. Inspector told me don’t use them they crack and blow off. I rounded up every brass and steel cap I could find. I was short one. During the night it cracked and blew off. Flooding out the house. I’d never use PVC for anything. Especially in the hostile confines of an engine room.

Yep, I've seen PVC fail as well. Sometimes it wasn't primed; sometimes the pipe was dirty or wet; sometimes it wasn't given enough time to cure, and sometimes PVC was used in place of CPVC. I also agree that an engine room is a harsh environment in terms of heat and vibration. So, I would agree with you insofar as pressurized plumbing supply lines go. FWIW, my marina's water supply is a steady 85 PSI. I wouldn't use PVC for that on a boat.

However, I disagree with universally condemning PVC in the face of its omnipresent use for several reasons. First, it's code around here. Second, I've had PVC in my commercial buildings for decades with zero issues. I have, seemingly miles, of PVC at the farm feeding the house, barns and outbuildings totally maintenance free. But, I have had to replace some iron and copper fittings that haven't stood the test of time.

The third reason I disagree with you is that an open AC condenser loop carries barely more than zero pressure. Now, I'm not saying the pipe can't fail. I am saying we've all seen hose clamps, for instance, give out or hoses burst in that harsh environment. So, properly installed PVC pipe above the waterline that is not rigidly terminated and used in very low to no pressure and drain applications makes sense to me. But you know those fumes make me see all sorts of pretty colors.

 

[Wiredup62]

Wiredup, thought I had some pix on my phone but don't.
Not sure when I will be back at the boat, the colder it gets the less likely since it's wrapped up and stored.
Check out the manifolds on Weaver Boatworks website.
There's other pix in some of their other builds too.

https://www.weaverboatworks.com/escapade-80/

Interesting. The weaver manifolds look fantastic. But, a little surprised at how they did the install of all the RW pumps at the sea chest. Doesn't seem like the cleanest.

 

[Cricket]

Thought the same thing about the Weaver sea chest, 2lbs of sh.t in a 1lb bag. Or, just close the lid....
Would be a nice problem to have. Spent quite a bit of time going thru the Weaver 97 footer, totally insane.

 

[racclarkson@gmail.com]

Not to put too fine a point on the discussion about using PVC piping in low pressure and above the waterline applications with proper soft terminations, I think the following might be useful.

Here's the water pressure reading 18" from the pump output before heading to the AC units.

Looks like about 8 PSI.

Here's the discharge water pressure before it starts a slight downhill run to the transom thru-hull.

Looks like 3-4 PSI.

The gauge isn't properly scaled for this low range of pressure, so it may be off a pound or two. Nevertheless, I think this indicates the danger of using PVC in this application presents negligible risks.

FWIW, I closed the discharge drain valve (for future de-scaling use), and the water pressure at the inlet rose to 18 PSI.

 

[SKYCHENEY]

I don't think pressure is the issue. I would be more worried about vibration and heat and how brittle that stuff can get with age.

 

[racclarkson@gmail.com]

Padded strapping. No UV exposure. No low temps. Temp measured well below 140 F in installed area. Most likely ac’s pushing water through piping during the hottest of conditions. No threaded joints. Above waterline. No siphon potential. I’ll let you know in a few years.