Seacocks replace or service?

[angus99]

Rod Collins’ articles describe the differing thread pitches typically between the older through-hulls and seacocks, which I found to be true on our DeFever. The SV seacocks and through-hull fittings were basically attached to each other by a couple of mismatched threads and some mastic—no through-bolting. I never put it to the test, but I doubt those connections would survive the 500-lb requirement. Add to that “backing plates” made of thin plywood, a couple of which had the consistency of wet pulp, and replacing all of the seacocks with modern Groco equipment was a no-brainer for me.

The SVs were very strongly built and several of mine were probably still serviceable. But replacing them with modern ball valves (with replaceable parts), robust flanged adapters (with matched threads that bite deep), and thick composite backing plates (epoxied to the sea chest and hull) was one of the first things we did when we bought our boat. Big bucks but no regrets.

 

[Steve DAntonio]

Once again, while I'm a fan of Groco products, I fail to understand the logic of there three piece through hull, flange and ball valve product https://www.groco.net/products/valves-seacocks/flanged-valves/ibvf-flange-adaptor It adds another set of threads, and another union which is a potential weak link that a traditional seacock does not have. Furthermore, a traditional seacock and thru hull have greater thread engagement as the threads are both NPS, rather than NPT, the latter, while strong, and matching, can't engage indefinitely, while a thu hull can be trimmed to engage nearly all of the threads within a flanged seacock.
The replaceable nature of the valve is of little value, good quality seacocks like their BV series last decades if not the life of the vessel. Having said all that, I don't believe the IBVF three piece threaded flange arrangement isn't ABYC compliant, I just don't see the benefit, and I do see some liability. Did I mention I really like Groco products?

Thread engagement examples attached, along with photos of a failed integral strainer/seacock..

ABYC Standards specifically prohibit the use of mismatched threads, BTW, so using a NPS thru hull with a conventional NPS thread ball valve is a clear violation, and one I encounter on an all to regular basis.

More here https://stevedmarineconsulting.com/seacock-selection-service-and-avoiding-the-pitfalls-2/

 

[C lectric]

I never liked the idea of the seastrainer hanging off the seacock, vertical or otherwise.. I have never had one but I just never liked it.

 

[angus99]

Steve, maybe Groco currently makes both through hulls and seacocks with the same NPS threads to current ABYC standards, but was that always the case? It certainly was not true on my 1987-vintage boat. (But I only know that the seacocks were Groco SVs, and can’t vouch for the through hulls. Possibly they were what the yard had on hand?) But whatever, the threads were mismatched and poorly engaged, as Rod Collins describes here: https://marinehowto.com/seacock-thru-hull-primer/.

With copious respect, I don’t understand how a flanged adapter would be any weaker from its second threaded connection than a traditional seacock might be from its connection to a barbed fitting. Additionally, there are three fewer “holes” in the boat with each flanged adapter since they are not through-bolted as with some (most?) traditional seacock installations. The through hulls and valves engage with the flanges deeply and the castings seem to be as robust as any other Groco seacock I’ve seen, so it’s hard for me to imagine the flanged adapters being a significant failure mode. To your knowledge have there been any reported failures attributable to flanged adapters?

 

[Steve DAntonio]

SDMC: Responses follow.

Steve, maybe Groco currently makes both through hulls and seacocks with the same NPS threads to current ABYC standards, but was that always the case? It certainly was not true on my 1987-vintage boat, but I only know that the seacocks were Groco SVs, and can’t vouch for the through hulls. Possibly they were what the yard had on hand. But whatever, the threads were mismatched and poorly engaged, as Rod Collins describes here: https://marinehowto.com/seacock-thru-hull-primer/.

SDMC: Among others (the combination thread), Rod is referring to NPS and NPT threads, which are entirely incompatible, and he does a good job of it as usual. Proper NPS thread seacocks have been around for many years, and they mate up with NPS thru-hulls. However, I can't vouch for every product, so there may have been products with unique threads.

With copious respect, I don’t understand how a flanged adapter would be any weaker from its second threaded connection point than a traditional seacock might be from its connection to a barbed fitting.

SDMC: The flange adapter has one additional joint, and its engagement with the thru-hull is shorter, fewer threads, so my point is, it offers no advantage.
Is it less strong? Maybe.

Additionally, there are three fewer “holes” in the boat with each flanged adapter since they are not through-bolted as with some (most?) traditional seacock installations.

SDMC: No seacock installation is required to be through bolted, in my experience few are, so there's no difference in installation for the flanged adapter and the traditional flanged seacock. If the flange has holes, they should be used, but not necessarily with through bolts, I don't specify through bolts on my installations, and Groco's own backing plate uses threaded inserts, not through bolts.

The through hulls and valves engage with the flanges deeply

SDMC: They are matching threads, NPS, that's true, but the engagement is shorter. Enough to make a difference? Probably not, but again I don't see the advantage to using these.

and the castings seem to be as robust as any other Groco seacock I’ve seen, so it’s hard for me to imagine the flanged adapters being a significant failure mode. To your knowledge have there been any reported failures attributable to flanged adapters?

SDMC: I've never seen a failure, but once again, why use these instead of a BV seacock, what's the advantage, how are they better?

 

[angus99]

SDMC: Responses follow.



SDMC: I've never seen a failure, but once again, why use these instead of a BV seacock, what's the advantage, how are they better?

I wouldn’t say better. But maybe just as good and easier to self-install (for me anyway)

 

[Steve DAntonio]

Yes, I'll grant you that, easier for one person to install;-)

Through bolts are an adjunct, they are really there to prevent the base from spinning, they aren't mandatory, they could be lag screws or machine screws screwed into the Groco base, as you've done, however, for those who actually make them through bolts, and they protrude into the seawater side, you should use bronze rather than stainless. At least one boat builder I know of, who has a very thick hull, installs them from the outside in, so they end up as studs, and they countersink the heads into the hill and epoxy over them, so they are encapsulated and captive.