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Old 11-11-2008, 02:45   #31
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I’m so surprised at the negative responses to the use of PVC on boats.

I’ve got no problem WHAT SO EVER in using sch 40 or 80 PVC pipe or fittings on my boat, the QA/QC is probably better than 80% no 90% of the garbage hoses that I see on many boats.
PVC ball valves vary greatly in quality. I’ve got no problem using good ones, however my sea cocks are bronze….that’s what came on the boat.
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Old 11-11-2008, 05:20   #32
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I use brass on the freshwater domestic system and if there was a failure I would at worst lose the water from the tanks into the bilge. On all plumbing with seawater I use bronze such as the head supply and waste fittings, seacocks and thru hulls, of course all double clamped.

Speaking of clamps - look for those which do not corrode. I believe you can find them in titanium now which won't rust. I will be changing out my clamps when I can find a source... Perhaps Sailors Solutions.
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Old 11-11-2008, 15:29   #33
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Hose Clamps from Titan are 100 Percent Titanium
for titanium hose clamps etc.
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Old 11-11-2008, 16:26   #34
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PVC OK With Me

Quote:
Originally Posted by James S View Post
Iím so surprised at the negative responses to the use of PVC on boats.

Iíve got no problem WHAT SO EVER in using sch 40 or 80 PVC pipe or fittings on my boat, the QA/QC is probably better than 80% no 90% of the garbage hoses that I see on many boats.
PVC ball valves vary greatly in quality. Iíve got no problem using good ones, however my sea cocks are bronzeÖ.thatís what came on the boat.
I agree, James. I used 1.5" sched 40 PVC pipe in my sanitation plumbing to my holding tank and a portion is below the water line...YIKES! I've had bad experiences with so-called marine sanitation hose. It degrades fairly quickly and the "stink" goes right through it. I was leery of using PVC so I did some "rube goldberg" testing to gauge its brittleness. I dropped a 35lb iron dumbell on the pipe from a height of 5ft on a concrete driveway and couldn't break or crack the pipe. I worry more about the rubber sanitation hose that comes out of my marelon seacock into the PVC section. One of the main reasons for PVC was the difficulty in installing a straight section of hose between two bulkheads 2.5 inches apart. I didn't want to replace rubber hose in this section every couple years. Even when the rubber remains OK, there is a calcification build-up from urine that eventually blocks the rubber hoses completely and makes them worthless. With the PVC, I can cap the lower end and fill the pipe with vinegar and "boil out" the pipe without removing it. I do worry about things that could sink my boat, but PVC pipe ranks below marine sanitation hose, marelon seacocks, hose clamps and escape hatches 2 inches above the water line put together with rivets (I fixed that one because I lost sleep over it).
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Old 11-11-2008, 18:21   #35
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I agree, James. I used 1.5" sched 40 PVC pipe in my sanitation plumbing to my holding tank and a portion is below the water line...YIKES!
Anyone who has followed my posts will know that I am very relaxed about using PVC (on our boat even the engine exhaust is Sched 80 PVC) and other plastics but for unplasticised PVC eg rigid Sched 40 & 80, it is subject to embrittlement as the temperature drops and that should be kept in mind for below waterline use.

At -10C (14F) its impact strength is typically around 1/4 of that at 20C (68F) but the drop in impact strength from that at 20C and that at the freezing point of water is steep with most occuring between 20C and 10C (50F) - at 10C impact strength is typically nearly half that at 20C but even that reduction is not a problem in use as these are typical working temperatures.

As you say though unplasticised PVC Sched 80 & 40 is very resistant to impact so is still so at the lower temperatures but is probably of concern enough to be wary about its use below the waterline. Of course if the boat is always in warm climates it may not be a problem but that poses the possibility (likely remote?) of a wet adventure for future owners or users of the boat if taken to colder climates.

In my own case I plan to use PVC for blackwater when replacement of the hose becomes necessary (it is a high quality industrial hose, not "sanitary" hose, so after 12 years is still non permeated) - however, for us everything, including all the holding tank pipework, is set up to be above the waterline except for about the last 1 foot in the discharge to the seacock - I anticipate using hose to bring the end of the PVC in the drop to the seacock above the heeled waterline, this part of the pipework being vertical and self draining so no permeation and calcification problems in it.
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