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I especially appreciate your input, Bob, since it’s based above all on educated engineering principles. If it’s true that a PVC manifold will pass muster with the federales, then it’s probably the the lesser of several evils and a smart, cost-efficient way to go.
Tor
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Silver Heels, P-424 #17
http://www.SilverHeels.us
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Did you find all-bronze shutoff valves to go with your bronze T’s? I’d like the ability to shut down one line at a time out without turning them all off at the seacock.
You and I are not alone in our original sin. I came across an Island Packet owners blog yesterday in which a proud skipper was showing off his new seawater intake manifold, all brass just like mine. I’ll bet there’s a lot of that going around. As you said, even your surveyor missed it. Lucky for me there are some savvy 424 owners on this list.
I’ll see what my welder has to say this afternoon. He’s very good and pretty reasonable. My thought is to have him weld half a dozen male nipples onto a length of 1″ or 1’1/2″ ID stainless steel pipe. Close off one end with a simple pipe nipple for the feed hose, and the other end with a removable plug for inspection/cleaning, and that’s about all there is to a manifold. Then I’ll screw ball valves onto the 6 vertical nipples, probably PVC (stainless valves cost $55 to $75 each!), then nylon hose barbs on top of the valves.
Hey, maybe I ought to start marketing these things. Seems like there’s a demand and no supply.
Tor
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Silver Heels, P-424 #17
http://www.SilverHeels.us
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Interesting problem. To make it more complicated, you can’t mix metal and plastic fittings unless you can find a way to ground each metal fitting. I don’t think you could find bronze thimbles anyway. I suggest contacting Forespar and asking them.
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Rich Carter
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Rich,
Why would you need to ground each piece of metal?
Tor
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Silver Heels, P-424 #17
http://www.SilverHeels.us
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Tor,
Yes, I used Groco valves (bronze bodies, SS ball valves) for each of the seawater users (frig, AC, galley). I left an additional valve (plugged) for future needs (water maker, etc.).
I think the grounding issue to prevent electrolysis of the metal parts by keeping all seawater immersed metal at the same electric potential. I didn't do that so maybe I'll have another project in a few years.On Mon, Sep 15, 2008 at 4:53 PM, Silver Heels < ([email][/email])> wrote:
Rich,
Why would you need to ground each piece of metal?
Tor
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Silver Heels, P-424 #17
http://www.SilverHeels.us
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Wow, John, that's probably the absolute best way to go and also the most expensive.
Bronze valves in seawater are electrically connected by the seawater so no strapping is necessary.
Bob
On Mon, Sep 15, 2008 at 4:42 PM, John Stevenson < ([email][/email])> wrote:
Tor,
Yes, I used Groco valves (bronze bodies, SS ball valves) for each of the seawater users (frig, AC, galley). I left an additional valve (plugged) for future needs (water maker, etc.).
I think the grounding issue to prevent electrolysis of the metal parts by keeping all seawater immersed metal at the same electric potential. I didn't do that so maybe I'll have another project in a few years.On Mon, Sep 15, 2008 at 4:53 PM, Silver Heels < ([email][/email])> wrote:
Rich,
Why would you need to ground each piece of metal?
Tor
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Silver Heels, P-424 #17
http://www.SilverHeels.us
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You have seawater running through the pipes. Your zinc will protect the bronze fittings if they are electrically at the same potential as the zinc. In other words, they must be grounded. If you have a plastic nipple or thimble in your manifold, you will insulate some of the metal pipes. If you have the whole thing connected to the through-hull using a rubber hose, the whole thing will be unprotected. IYou can fix this by bonding the metal parts. The same thing applies to raw water strainers, V-drive, and anything else that transports seawater. f you use Teflon tape to assemble your manifold, you will insulate the fittings. I think pipe dope would be OK.
While typing this, I thought of a problem with my engine installation. The transmission oil cooler is painted. It uses seawater to cool the transmission fluid. Although it is in contact with the engine block via mounting hardware, the paint might insulate the cooler. I need to make sure that it is properly grounded.
I still think that the fittings used for home sprinkler systems might be a good choice. I’ll have to look at them the next time I’m at home depot. The valves might not be up to standard, but the thimbles might.
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Rich Carter
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Thanks, Rich. I guess you saw Bob’s comment that bronze valves in seawater are electrically connected by the
seawater so no strapping is necessary. The plot thickens.I’d be surprised if a home sprinkler system was made of bronze or stainless steel. Seems like an unnecessary
extravagance, but would be delighted to learn otherwise.Tor
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Silver Heels, P-424 #17
http://www.SilverHeels.us
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Hi Tor,
I still stand by plastic – none of us are going to live long enough to see it degrade. Bronze thru-hull fittings are a MUST because of the resistance to lateral loading. Bronze and plastic will work but I don't really see a tremendous improvement in either reliability or longevity.
The whole bonding thing is up for discussion still. Do you bond? Do you bond to ground? Many new boat manufacturers don't bond at all because they feel that electrically connecting all the fittings will create a situation in badly grounded marinas where all the fittings will corrode.
Who knows? You could argue both ways and it's a little like politics or religion. I may not agree with you but I'll defend your right to build your manifold out of whatever you want…
Anyway, mine's plastic and hose. If you don't hear from me one day, it's because it wasn't the right choice. Oh, well. 🙂
Bob
On Tue, Sep 16, 2008 at 6:26 AM, Silver Heels < ([email][/email])> wrote:
Quote:Thanks, Rich. I guess you saw Bob's comment that bronze valves in seawater are electrically connected by the
seawater so no strapping is necessary. The plot thickens.I'd be surprised if a home sprinkler system was made of bronze or stainless steel. Seems like an unnecessary
extravagance, but would be delighted to learn otherwise.Tor
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Silver Heels, P-424 #17
http://www.SilverHeels.us
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Well you all forced me to go dig out my old Calder (actually it is a new one, my old one wore out).
Calder recommends against bonding bronze thru-hulls and other bronze plumbing so long as they are isolated from other metal components or not immersed in seawater that could contain stray electrical current (e.g., the bottom of the bilge). His reasoning is that bronze is so much more noble that most other metals that may be bonded to the zinc that the bronze will only accelerate the destruction of the zinc then the destruction of the bonded metals that the zinc was supposed to protect.
That seems to let me off the hook for my manifold, except he goes on to recommend against bronze ball valves with SS balls (my Grocos).
I've decided to exercise my right to selectively accept the advice of experts. So I'll stay with my unbonded manifold with SS ball valves. I'm pretty comfortable with the latter position as it appears all of the original valves on my 424, with the exception of one, are bronze ball valves with SS balls. The one exception is the valve for the deck scupper under the aft berth. That is a true bronze seacock. Having lived on board for nearly 5 years and cruised for 3 years I got out of the habit of closing and opening the valves on a regular basis. This year before my haulout I found nearly all were frozen so during the haulout I worked on all of the valves. Power washing the hull freed up most of them – just a few barnacles on the ball. Others only required a light tap with a hammer to open. I checked the balls in all of these valves and could see no deterioration. If they have lasted with about zero maintenance for 30 years I'm not worried about the valves I just installed.
Anyway that's my rationale and I'm sticking to it :).On Tue, Sep 16, 2008 at 8:26 AM, Silver Heels < ([email][/email])> wrote:
Quote:Thanks, Rich. I guess you saw Bob's comment that bronze valves in seawater are electrically connected by the
seawater so no strapping is necessary. The plot thickens.I'd be surprised if a home sprinkler system was made of bronze or stainless steel. Seems like an unnecessary
extravagance, but would be delighted to learn otherwise.Tor
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Silver Heels, P-424 #17
http://www.SilverHeels.us
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Hi John,
That's really what it all boils down to. Experience and results. Bronze and SS should be good as long as the valves are operated. Bronze and bronze is also good, but needs to be operated AND greased. Bronze/SS and plastic is totally fine. I wouldn't replace a thru-hull with plastic under any circumstances, and wouldn't put a SS fitting that was continuously under water.
The fact is that as long as you keep up on maintenance and minimally inspecting your gear, you should be good. This group falls well inside of that category. Also, the fact that we even consider the best solution says a lot.
In 30 years, we'll all get together for a beer and a check of our manifolds.
Bob
On Tue, Sep 16, 2008 at 7:20 AM, John Stevenson < ([email][/email])> wrote:
Quote:Well you all forced me to go dig out my old Calder (actually it is a new one, my old one wore out).
Calder recommends against bonding bronze thru-hulls and other bronze plumbing so long as they are isolated from other metal components or not immersed in seawater that could contain stray electrical current (e.g., the bottom of the bilge). His reasoning is that bronze is so much more noble that most other metals that may be bonded to the zinc that the bronze will only accelerate the destruction of the zinc then the destruction of the bonded metals that the zinc was supposed to protect.
That seems to let me off the hook for my manifold, except he goes on to recommend against bronze ball valves with SS balls (my Grocos).
I've decided to exercise my right to selectively accept the advice of experts. So I'll stay with my unbonded manifold with SS ball valves. I'm pretty comfortable with the latter position as it appears all of the original valves on my 424, with the exception of one, are bronze ball valves with SS balls. The one exception is the valve for the deck scupper under the aft berth. That is a true bronze seacock. Having lived on board for nearly 5 years and cruised for 3 years I got out of the habit of closing and opening the valves on a regular basis. This year before my haulout I found nearly all were frozen so during the haulout I worked on all of the valves. Power washing the hull freed up most of them – just a few barnacles on the ball. Others only required a light tap with a hammer to open. I checked the balls in all of these valves and could see no deterioration. If they have lasted with about zero maintenance for 30 years I'm not worried about the valves I just installed.
Anyway that's my rationale and I'm sticking to it :).On Tue, Sep 16, 2008 at 8:26 AM, Silver Heels < ([email][/email])> wrote:
Quote:Thanks, Rich. I guess you saw Bob's comment that bronze valves in seawater are electrically connected by the
seawater so no strapping is necessary. The plot thickens.I'd be surprised if a home sprinkler system was made of bronze or stainless steel. Seems like an unnecessary
extravagance, but would be delighted to learn otherwise.Tor
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Silver Heels, P-424 #17
http://www.SilverHeels.us
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Tor
No disrespect to Bob, but I think he is mistaken in this case.
From the following link:
http://www.yachtsurvey.com/corrosion.htm“The general rule is that anytime a piece of metal plumbing or hardware is isolated in a system, as with a sea strainer that is joined by two hoses is electrically isolated, needs to be wired into the system. This can be done by daisy chaining items together, but it’s a good idea not to include too many items in a chain. Obviously, at any point where a connection is broken, all those items upstream will be unprotected.”
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Rich Carter
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Hey guys
I’m still reading up on the bonding issue. My mechanic said that I should not bond the prop strut when I was repowering. He suggested putting a zinc on the strut next time I haul out. He said that if there was some stray current wandering around that it was better for one through hull to dissolve than for all of them to slowly go at the same time. I’m reading Nigel Calder’s book to see what he has to say. It does seem to be a mix of religion and politics and black magic. Everyone’s got one and that’s all I have to say about that.
Linus<.. snip>
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Religion, politics and black magic? You would think we are talking about ground counterpoise for HF radio!
But wait, that has some Voodoo too…
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This is sounding more and more like a B horror movie – scary and funny at the same time. Maybe PVC is the way to go after all, at least for us tropical sailors.
Tor
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Silver Heels, P-424 #17
http://www.SilverHeels.us
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Hi Tor,
Emotion and other opinions aside, let's look at the system requirements.
1. You need to distribute salt water (corrosive) to several points at a pressure of 1.5 pounds static.
2. Falling off a 50 foot wave will induce a pressure spike of 25 pounds or so, giving a dynamic and static pressure total of 27-30 psi.
3. PVC (Schedule 40) will withstand 120 psi 140 degrees.
4. You will die at sustained temperatures of 140 degrees.
5. PVC doesn't corrode.
6. You and anyone on your boat will not be walking, stepping, jumping, chewing, drilling, sawing, jackhammering or any other destructive processing on the PVC.
7. Occasionally, you'll be having a look at the PVC. Maybe even operating the valves.
8. You will live less than 100,000 years (the estimated life of PVC in seawater). The boat will survive less than 100,000 years. You will sell the boat before 100,000 years pass. You get the idea.
9. PVC is easy to construct and install
10. PVC is cheap and is not subject to galvanic or other metallic corrosions.
11. PVC is a well understood and tested material.
That's about it. Admittedly, my investment into my home is less than yours, but I trust what works for a bazillion homes and industries to work in the relatively benign environment I've put it to work. I've used PVC in nuclear applications. Not irradiated but in water treatment.
What it boils down to is new materials in new uses – tradition, which is all important in marine applications – is subject to new tests and new applications. I really believe it's ready for prime time in underwater applications. When ships were of wood and men of iron then valves of bronze were de rigeur. New times, new materials, new processes.
When all is said and done, an engineered material is useful within it's design parameters. PVC falls well within those parameters.
And now, I've said all I'm going to. You can spend 100 or 200 dollars on bronze. You can bond you boat everything to everything. Or for around 60 dollars you can have a manifold that will last of 100,000 years. Maybe more.
But, that said, I'm not a licensed engineer. So your results may vary. As I said before, in 30 years we can compare manifolds. I'll bring the wine and beer. And Yukon Jack, the official drink of Pelican. 🙂
Bob
2008/9/16 Silver Heels < ([email][/email])>
Quote:This is sounding more and more like a B horror movie – scary and funny at the same time. Maybe PVC is the way to go after all, at least for us tropical sailors.Tor
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Silver Heels, P-424 #17
http://www.SilverHeels.us
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