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Old 21-09-2008, 19:31   #1
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Home Depot Plumbing fittings - just bad or really bad?

Without going into details, I am considering using a couple of schedule 40 in-line PVC ball valves, hose barbs and assorted fittings to direct and control the flow of cooling seawater to A/Cs and water maker.

Before the howls of derision - please note: These fittings will be inboard of a Vetus strainer, thru hull and sea cock. All fittings will be on the suction side. All hoses will be marine quality or whatever it is that West Marine recommend and sell.

Why I am I considering this? - PVC is corrosion resistant, lighter, its neater looking and maintenance free (at $6, its a throw away item).

I have a nagging feeling this may not be one of my better ideas but I cant quite figure out why.

Comments?
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Old 21-09-2008, 19:35   #2
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I'm not going to deride you, just give you the facts. Never use PVC for anything on a boat where if it breaks, it could sink your boat. PVC is just not strong enough. One good kick, slip or if something lands on it, it could break. The cheap price is not worth the risk of sinking your boat. For non-critical applications that cannot sink your boat, then no problem. The problem is, most of those hoses running around your boat below the waterline do have the potential of sinking your boat. For non-critical piping you may want to use ABS instead of PVC.
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Old 21-09-2008, 20:07   #3
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I used them before the freshwater pump as a way to winterize the fresh water system. They don't take any pressure and the water tank is lower than the valves. Somethings work and other things don't. Owning a boat is not inexpensive and sinking one is just plain foolish.
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Old 21-09-2008, 20:30   #4
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I agree it was a dumb idea.

I just needed re-assuring how dumb it was.

The cost differential is inconsequential $6 versus $50 - peanuts in the grand scheme of things - and was never my motivation.

Its just those white PVC valves with red handles looked real purty.

I'll go to the clunky marine approved stainless steel ball valves.

Thanks for setting me back on the straight and narrow
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Old 21-09-2008, 20:31   #5
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for the want of a nail>>>>
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Old 22-09-2008, 01:42   #6
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Your boat won't pass a survey if it has PVC below waterline. Also, consider Marelon valves. No corrosion, looks good.
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Old 22-09-2008, 06:46   #7
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PVC ball valve NO, assorted HD hose barb fittings are fine.
Just as side note. If at all possible I always make my hose from through hull runs above the water line mark before I use any fittings and secure them just in case one does break, comes loose or breaks (90 degree hose barbs have the highest tendancy to break, I don't use them) and double reverse clamp everything. Just my two cents..... but I'm over paid.
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Old 22-09-2008, 07:07   #8
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Thanks - everyone - I get the point !!.. Rest easy. I have exorcised the PVC demon and expunged the idea permanently.

Like most of my hare brained projects - this one started off with the all too familiar phrase :- "....it seemed like a good idea at the time.."

Tellie - thanks for the advice about elbows - I did not know they were failure prone, I'll avoid them.

Chief Engineer : I'm guessing the nails you needed were to crucify me? (you'll need to join the ever lengthening queue).
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Old 22-09-2008, 08:22   #9
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Be careful..

Quote:
Originally Posted by Tellie View Post
assorted HD hose barb fittings are fine.

Be very very careful with the above advice:

#1 Home Depot / Home Center hose barbs are usually either nylon, yellow brass or PVC. Yellow brass and bronze should never be mixed bellow the waterline or in a system other than the domestic, on board, drinking water. Nylon and PVC as we all know should also not be used bellow the waterline. Bellow the water or connected to it should always be marine rated bronze or marelon. I am too uncomfortable with the new generation of stainless valves, having seen some bad crevice corrosion and galvanic issues, to personally recommend them for bellow water applications.

#2 HD hose barbs are usually "shorties"! Other than a few of the PVC ones they are to short to fit two hose clamps for bellow waterline applications. These short barbs in most cases do not allow for the clamping of two good quality hose clamps within the barbs length. I have seen far to many "double clamped" hoses where the second hose clamp clamped nothing but hose...!


Not all hose barbs are created equal!!!!

Here is what can happen in less than one years time with a yellow brass Home Depot ball valve. The bronze thru-hull was perfectly fine showing no signs of dezinctification.

The ball is totally missing!!!

Note the pinkish coppery hue near the big corrosion spot! This valve was literally weeks away from sinking this boat. One year!!! Also note the "shorty" brass barb good luck getting two clamps on there and having the second one do any good...
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Old 22-09-2008, 09:29   #10
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I looked at the PVC valves there, if you check they have steel parts in them a small ring.

One thing to keep in mind the cost to replace thru hull is not something you will have every year so i would say not the place to try and save money.

I replaced one thru hull right before i had the Dutch put in (now i wish i had all them done) the cost was around $150 for all the parts but i am very happy i took the advice from others on here.

PS. This is why i love this site so much, the people here tell the resaon behind things and not just "don't do that" big differance to me.

John
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Old 22-09-2008, 09:47   #11
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Neelie was contemplating commodity type PVC valves for internal control and service applications, not as Seacocks or at Thru-Hulls.
His was a good question, which received several good answers.
I believe that “Marelon” is a UV stabilized Fibreglass Reinforced Nylon polymer.
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Old 22-09-2008, 10:54   #12
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Maine Cat uses Schedule 40 pipe between the heads and the holding tank on the 41. If Dick Vermeulen approves something, its gospel in my book.
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Old 22-09-2008, 13:44   #13
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More Info : PVC not necessarily the AntiChrist.

Upon further reading - I notice that Steve Dashew in his Encyclopedia (1997 Edition pg. 802) has no qualms about using them.

Also Saint Nigel - patron saint of all things yachtlike - uses PVC pipes (Boatowners Mechanical and Electrical Manual, 2nd Ed. pg 361)

Thus its very odd that someone stated that PVC pipes and fittings wont pass survey now - one possibility could be that my books are pretty old and out of date and standards have since changed.

Given that Dashew and Calder are unopposed to the idea of PVC pipes and fittings, perhaps it was'nt such a stupid idea after all. Although, in their day, all this stuff was made in the USA where quality and standards are always assured. Nowadays, all this stuff is made in China only. The quality of material and construction of anything from the PRC is always questionable. In the end thats what made me think twice.

But chill out everyone - I too have succumbed to the scare campaign and ordered a pair of Marelon valves and fittings. Woe betide the lot of you if these two should ever fail! (or if I discover that these too are now made in the PRC).
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Old 22-09-2008, 16:32   #14
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Quote:
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Without going into details, I am considering using a couple of schedule 40 in-line PVC ball valves, hose barbs and assorted fittings to direct and control the flow of cooling seawater to A/Cs and water maker.
There is nothing wrong with using plastic fittings and valves as long as they are protected (just as any small diameter pipeword should be even if metal). Contrary to the responses from some others I take it that you are not talking about using rigid PVC pipe, just fittings and valves.

I would recommend though that if it is below the water line you use threaded engineering polypropylene fittings which are good for typically close to 250 psi (there are also fibre reinforced ones but are harder to find) and plastic engineering ball valves. These are normally available from any plumbers merchant - I am not familiar with what USA Home Depots stock, but may be available from them too. Above the waterline (say at least 200mm above) then rigid PVC is fine and often the material of preference in high quality builds (eg as Sandy points out, for black water).

In our own boat we have the polypropylene fittings and plastic ball valves (it was a professional custom build) below the water line for the seawater distribution headers after the seacocks with no problems at all. They are located so that they are protected from accidental physical damage. Our engine exhaust, which discharges above the waterline, is an example of something we have fabricated from rigid PVC pipe.

From the surveys I have seen the greatest cause of flooding accidents in boats is by far from failed metal pipework (ie after the seacocks) so metal solutions are not free from their own problems. Plastics will last the life of the boat, they (like any small diameter fittings and pipework whatever the material) just need to be protected from physical damage.

Regarding passing survey for commercial vessels, in the jurisdiction I work in plastics are accepted by local rules as it has been in vessels built to the rules of classification societies that I have been involved with. The usual limitations just being that the material is suitable for the task, including suitability for the fire rating of the compartment they are in, and properly installed for the service. Personally, I believe that would exclude the use of rigid PVC below the waterline in seawater services - it does not exclude other plastics however.
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Old 22-09-2008, 17:11   #15
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PVC plumbing is often used on larger yachts, for domestic water, grey and black water. It must be installed where there can be no flex/risk of bending. Not normally seen on smaller boats because the runs are so short. No problem with PVC.

Just dont use it for raw water and connections for under the waterline.
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