PVC Pipe for a Wet Exhaust ?

[SabreKai]

I noticed that the Vetus mufflers I got from Irish Queen were all attached to PVC pipe instead of wire reinforced hose. Anyone have any comments on this practice? I am thinking that doing the exhaust from the muffler to the exhaust port on the transom in PVC would solve a lot of routing problems.

[barnakiel]

Sure it was PVC?

If the exhaust is cold then who knows maybe it will work fine. How does PVC interact with sulphur / acids / etc.?

b.

[MikeTurner]

I know PVC pipe isn't recommended for plumbing from the head to the holding tank because the rigid pipe won't "give" with the movement of the boat. So I wonder if a similar issue would exist for long runs of PVC pipe in the exhaust? Over time the PVC fittings might work loose allowing exhaust water and gases into the boat?

[s/v Jedi]

These plastic Vetus exhaust parts quickly burn up when seacock is closed or impeller broken (any time no water flows). Better go with Centek parts. They make waterlifts, separators etc. but also pipe, 45- and 90-degree elbows etc. These are fiberglass parts so can easily be modified, laminated into hull etc.

cheers,
Nick.

[Target9000]

When we install our engine and redid the exhaust plumbing our vendor told us the same thing Nick said... We had an old Vetus muffler and replaced it with a Centek. If for some reason you don't have water being injected into the exhaust line the heat of the exhaust will melt through most materials. Why take a chance?

[GordMay]

ABYC "P-1", doesn’t list PVC in it’s extensive list of approved materials for engine exhaust systems, and I wouldn’t recommend it for such use.
I would second the recommendation for Centek Fibreglass Reinforced Plastic, meeting the UL 94V-0 Flammability test, in a Wet Exhaust system.

“INSTALLATION OF EXHAUST SYSTEMS FOR PROPULSION AND AUXILIARY ENGINES”
P-1 ➥ http://www.abycinc.org/committees/P-01.pdf

[David M]

No way, not for exhaust. It is too brittle and has too low of a melting point. Yes, it might work for a while. But is might good enough?

One can only go cheap to a point where you then start endangering lives and sacrifice reliability.

[s/v Jedi]

wow... it's not often that everybody agrees with me... there must be something wrong (especially since Vetus is Dutch like me :-)

ciao!
Nick.

[David M]

Nothing wrong...just a random coincidence.

[capn_billl]

PVC has too low of a melting point for Exhaust, even on a good day as the temp increases the strength decreases, allowing it to deform and possibly leak. I like PVC and use it a lot, but I would never use it for that. Also it burns easily giving off poisonous gasses. It can even outgas chloramines when heated.

[foggysail]

Originally Posted by MikeTurner

I know PVC pipe isn't recommended for plumbing from the head to the holding tank because the rigid pipe won't "give" with the movement of the boat.

REALLY???? Sure is much better than stink hose!

Foggy

[JeremyK]

Old thread, but I came across this while in the process of designing the exhaust on my "new to me" Nor'Sea kit.

I do find it a bit curious that "reinforced plastic" is allowed as part of the silencer or waterlift chamber but is not listed as acceptable for "exhaust pipe". If anything, piping after the waterlift would have an even lower temperature requirement than the silencer/waterlift muffler itself. Wouldn't that also technically mean that you couldn't use fiberglass elbows and 45 degree transition pieces as part of the exhaust system (connecting exhaust hose to exhaust hose)?

The only version of the ABYC doc. that I found was from 1993. There have been just a few improvements to "plastics" over the years that would suggest an update to Table 1 is necessary.

For example, I came across this product: https://www.usplastic.com/catalog/it...x?itemid=36087

Granted, "non-combustible" does not necessarily mean UL-94 V0 but the rated working temperature is pretty impressive.

• Comparable corrosion resistance to PVC pipe
• Not UV stabilized
• High tensile strength
• Low thermal conductivity & low flow resistance
• Non-combustible
• Working temperature: 33°F - 200°F
• NSF 61 listed
• Dimensions: 2.375" OD x 0.218" Wall
• Maximum pressure: 200 psi

[s/v Jedi]

Originally Posted by JeremyK

Old thread, but I came across this while in the process of designing the exhaust on my "new to me" Nor'Sea kit.

I do find it a bit curious that "reinforced plastic" is allowed as part of the silencer or waterlift chamber but is not listed as acceptable for "exhaust pipe". If anything, piping after the waterlift would have an even lower temperature requirement than the silencer/waterlift muffler itself. Wouldn't that also technically mean that you couldn't use fiberglass elbows and 45 degree transition pieces as part of the exhaust system (connecting exhaust hose to exhaust hose)?

The only version of the ABYC doc. that I found was from 1993. There have been just a few improvements to "plastics" over the years that would suggest an update to Table 1 is necessary.

For example, I came across this product: https://www.usplastic.com/catalog/it...x?itemid=36087

Granted, "non-combustible" does not necessarily mean UL-94 V0 but the rated working temperature is pretty impressive.

• Comparable corrosion resistance to PVC pipe
• Not UV stabilized
• High tensile strength
• Low thermal conductivity & low flow resistance
• Non-combustible
• Working temperature: 33°F - 200°F
• NSF 61 listed
• Dimensions: 2.375" OD x 0.218" Wall
• Maximum pressure: 200 psi

Didn’t read the thread but do you know the Centek products incl, exhaust pipe?

[MicHughV]

True story.
When I built my boat, I used galvanize steel pipe to route the exhaust/water from muffler to hull outlet. The boat being a center cockpit, the exhaust had a relatively long run under the aft bunk
After a period of time, this galvanized pipe rusted thru' from the inside and began to leak.
So I installed pvc pipe in it's stead and it worked fine as long as there is water flow inside the pipe. The pvc pipe would get warm to the touch, but not so much that you couldn't hold it. The way that pvc pipe was routed meant that there was always some residue water in it.
I ran my boat that way for number of years and never had a problem. Mind you, it was only a small engine, 22 hp, a larger engine may present problems.
Would I recommend it, no, probably not, but depending on how the exhaust/water is routed it can work, the key being to ensure that the interior of the pipe has an adequate flow of water.

[GordMay]

PVC [Polyvinyl Chloride] can handle temperatures up to 140°F [60°C] maximum; while CPVC [Chlorinated Polyvinyl Chloride] handles temperatures up to 210°F [99°C].

But, PVC will start to sag at about 130°F, and the the normal operating temperature, of most marine diesels, is [typically] 185°F [85°C].

Technical Manual ➥ https://www.kebechem.com/fiches_tech...e_pvc_cpvc.pdf

Typical maximum operating temperatures for common plastic pipe materials [ABS, PE, PVC, CPVC, PB, PP, & SR] are indicated below. Note that working pressure varies with type of material and schedule (wall thickness).
➥ https://www.engineeringtoolbox.com/p...re-d_1621.html

The pressure ratings given for PVC pipe are for a 73°F operating temperature.
To reduce the pressure ratings of PVC pressure pipe for operating temperatures above 73°F, multiply the pressure rating or pressure class by the following derating factors:
At 80ºF Multiply by 0.88
At 90ºF Multiply by 0.75
At 100ºF Multiply by 0.62
At 110ºF Multiply by 0.50
At 120ºF Multiply by 0.40
At 130ºF Multiply by 0.30
At 140°F Multiply by 0.22