# Basics of Seacocks, Thru-Hulls, Valves



## Jaywalker (Dec 16, 2009)

There's a lot on the forum about how to rebuild, repair, and avoid problems with seacocks, thru-hulls, valves, and so forth, but I haven't been able to locate any really basic info on them. I think I understand the reason for a thru-hull, but that's about the extent of my knowledge.

Is every valve you put in a thru-hull a seacock? If not, what constitutes one?

What constitutes a good valve, and why?

Are there any cutaway diagrams of the various approaches?

Or - "What's a better way to ask the question?"

Thanks.


----------



## CalebD (Jan 11, 2008)

See this: Seacock & Thru-Hull Primer/Pre Information Photo Gallery by Compass Marine at pbase.com
this: Replacing Thru-Hulls and Seacocks Photo Gallery by Compass Marine at pbase.com
and this: Seacock Backing Plates / Alternate Method / No Through Bolts Photo Gallery by Compass Marine at pbase.com

These should answer all your questions.
Thanks MaineSail


----------



## Jaywalker (Dec 16, 2009)

Thanks, CalebD. I finally found the SailNet link (http://www.sailnet.com/forums/gear-maintenance/45368-seacock-vs-ballcock-ball-valve.html), which led me to one of those. I hadn't seen the others: thank you - it does clear things up.

Mostly. Do the flange bolts screw into the hull, or through it to be bolted and bedded on the outside? Disregard - found that, too - through and bedded.


----------



## jaschrumpf (Jun 22, 2002)

The topic of this thread leads me to ask my own question: on my boat, a 1975 Newport 28, there are just smooth-sided holes on the bottom of my hull where the through-hulls are. No mushroom head, no sign of any bronze ring or fitting at all. Just a smooth hole in the fiberglass hull barely big enough to put my index finger in.

Does this mean (1) that replacing the old gate valves with ballcocks will be a simple matter of just unscrewing the old valve off the through-hull fitting and replacing it with a nice new ballcock, or (2) I will end up having to grind the old fitting out from under a quarter-inch of fiberglass to remove it and pay someone for the removal and repair? To my hopeful eye, it appears that I can unscrew the old one and replace it.

I'll include a photo of the gate valve in question if you promise not to make rude comments about the filthy state of the engine room. Apparently the POs were unfamiliar with cleaning agents of any time, nor did they ever bother to wipe up any spills.

You promise? OK, here's the photo. The blue and red valves are a ballcock a PO put in to keep from having to crank the gate valve every time he wanted to use the motor (yes, I know, and the gate valve turns very easily but is awkwardly placed and takes a while to open and close), and the ballcock I added for the convenience of having a simple way to provide alternative coolant from a bucket or wherever (there's a garden hose fitting on the end of that valve).


----------



## btrayfors (Aug 25, 2006)

Scares the heck out of me! That's a sinking waiting to happen. You're right to want to change it for a proper seacock arrangement.

My guess is that you cannot just unscrew it. Rather, there's very likely to be a flange under the fiberglass outside the hull. You'll likely have to dig it out, prep the area for a new thru-hull, prep the inside of the hull, make a proper backing plate, attach a proper seacock with a triangular base and bolts, etc., etc.

MaineSail has posted a number of wonderful pix on his website (links above by CalebD) which will help to guide you thru this. You may want to have a professional do it, or at least be sure you read up and then watch "the professional" do it to be sure it's done right.

This will not be easy or cheap, but it's critical that it be done right!

Also, lose the "alternative" way to get coolant, etc. A bucket over the side does very nicely when you need seawater, and you don't want to use seawater in your engine anyway, as that's a good way to speed it toward its demise. Use only 50-50 mix of coolant.

Bill


----------



## mitiempo (Sep 19, 2008)

Jaywalker
The flange bolts conventionally go through the hull from the outside in, heads countersunk outside amd the small recess filled over as Maine Sail's site shows. He also shows an alternative if you don't wish to drill the holes through the hull here Seacock Backing Plates / Alternate Method / No Through Bolts Photo Gallery by Compass Marine at pbase.com

jaschrumpf
Agree with Bill. Many boats (some Catalina 30s among others) have the mushroom flush on the outside and glassed in. The gate valve I'd throw away and install a proper mushroom with flange with a ball valve attached as Maine Sail shows. As far as adding coolant from a bucket for winterizing I'd do it by removing the other end of the hose fron the strainer - you do have a strainer?


----------



## degreeoff (Oct 25, 2009)

not to hijack, but you raised a point that I do not know if I need to address on my Catalina 30 (85). It has said flush mushroom heads and 1/4 turn black plastic of some sort valves that all turn freely. Do I need to worry about these or are they of good caliber?

Thanks

Josh the Arggg Hijacker.


----------



## Maine Sail (Jan 6, 2003)

jaschrumpf said:


> You promise? OK, here's the photo. The blue and red valves are a ballcock a PO put in to keep from having to crank the gate valve every time he wanted to use the motor (yes, I know, and the gate valve turns very easily but is awkwardly placed and takes a while to open and close), and the ballcock I added for the convenience of having a simple way to provide alternative coolant from a bucket or wherever (there's a garden hose fitting on the end of that valve).


Ok, I promise, and will keep it specifically to the seacock system.. 

Honestly I could care less about the dirt but that seacock configuration is about the most manifestly unsafe one I've seen in a long time! Even if that were a bronze or Marelon, flanged seacock I would still feel uncomfortable with the height and sheer length and the miscellany of nipples and valves that create the hard lever you have working against that seacock.

The raw height of the combination of fittings combined with the non-Marelon gate valve makes this totally scary. Marelon, Bronze or stainless but NOT nylon, PVC or acetal. Seacocks designed to meet UL1121 & ABYC must be able to withstand a 500 pound static load at the inner most hard fitting. Yours is nearly 12" high, guessing here, before it even makes a right ancgle and continues and may not even withstand 20 pounds of force before snapping that plastic, most likely PVC, valve...

I would guess that you do have a bronze flush mount thru-hull based on the lock nut in contact with the well weathered, apossibly saturated and potentially punky backing plate. You may be able to thread that contraption off and replace it with a bronze UL marine rated ball valve but you may also break the seal and need to re do the whole thing. If it is a recessed flush mount thru-hull be VERY careful removing and re-bedding it as many of the companies that made them are now long gone and replacement sizes are not always the same..

Please do yourself a favor and fix this as soon as possible and shorten your overall hard piping height and length.. Whenever possible the last hard fitting on the inside of a seacock should be a pipe to hose adapter. No nipples, tees or multiple valves etc. etc.. You want to get to soft piping as soon as possible to reduce the lever effect on the valve.

It also appears you have a venerable corrosion cocktail with what looks to be a mix of brass, bronze and non UL marine rated ball valves of questionable metalurgic makup. All metals in a seacock system should be galvanically compatible. Yellow brass nipples and bronze elbows are not very well suited for each other, when mixed together, in this environment. I have seen home ceneter brass valves corroded away in less than a years time yet the bronze thru-hulls they were connected to were still perfectly fine..

P.S. NEVER connect a pressurized garden hose directly to that fitting!! It is ok to let the motor suck from a bucket but not ok to pressure feed it. That is if you don't want a motor full of water...


----------



## redhead78 (Dec 7, 2009)

*seacocks*

Hey guy you have a bit of a mess there, but b-4 you panic,if you deceide to remove this, try removing what looks like 2 ball valves installed over an old open broken gate valve.Then you will be looking at the original gate valve which is open, soak it with penetrating oil, let it sit a day, really soak it. Then with a wrench on the old seacock nut,[the green one closest to the inside of the hull], try to carefully remove the old gate valve. If this works get a quality ball valve[ Groco] clean up the threads and install it on the old seacock threads.Maybe use teflon tape, then install the proper fitting for your water system in the top of the new valve.I guess the only valves around the 70,s were those crap gate valves,I have a frozen one I have to change on my 1977 Jeanneau. Red


----------



## jaschrumpf (Jun 22, 2002)

Thanks for all the input. I've had the whole thing above the original gate valve apart in the past year, so nothing is frozen and the original old gate valve works fine. Moves smoothly to open and close, it's just awkward to reach and one can only turn the handle a little at a time, which is why a PO must have put the ballcock valve on top of it. Would be a lot easier if the handle faced forward instead of aft.

The moment of leverage does bother me though, so I'll disassemble that and return it to a more natural state.

I do know enough to not run a pressurized hose to the system. That hose fitting is for a 4' piece of garden hose I run into a bucket of antifreeze for winterizing, and that's all.


----------



## Maine Sail (Jan 6, 2003)

Jas,

A big part of the problem is the material used in that gate valve..

This is a quote directly from the USCG..



USCG said:


> The Coast Guard specifically advises against the use of PVC components in vital systems, especially in sea water intake systems and pressurized piping systems.


----------



## jaschrumpf (Jun 22, 2002)

I'm not arguing. This goes on the list of things to do in spring when I have her hauled for painting. There's another gate valve still on the boat that looks new, but it also looks like a Home Depot special. It'll go too.

I'm not especially surprised. You should have seen the wiring that I replaced last year...


----------



## Maine Sail (Jan 6, 2003)

jaschrumpf said:


> I'm not arguing. This goes on the list of things to do in spring when I have her hauled for painting. There's another gate valve still on the boat that looks new, but it also looks like a Home Depot special. It'll go too.
> 
> I'm not especially surprised. You should have seen the wiring that I replaced last year...


Ouch and double ouch on the wiring..

I just hate to see anyone loose a boat over something so easily preventable. I have personally had a PVC elbow, that was used by a big name builder back in the 80's, crack in my hand as I attempted to remove it. Fortunately this boat was on the hard at the time. I have a friend who had one threaded onto a bronze thru-hull by a PO and the PVC valve split at the threads due to differing expansion and contraction issues. His boat was in the water at the time and the leaking prompted him to rmove and replace it....


----------



## lpbosch (Oct 20, 2015)

Does anyone have the size and number of thru hulls on a 1981 C30?


----------



## ottos (Aug 12, 2008)

I take it you mean Catalina 30?

If so, try to call them at this link.


----------



## lpbosch (Oct 20, 2015)

Thank you Ottos. I did just that yesterday and got the answer I was looking for. Again, thank you for your help.


----------



## miatapaul (Dec 15, 2006)

lpbosch said:


> Does anyone have the size and number of thru hulls on a 1981 C30?





lpbosch said:


> Thank you Ottos. I did just that yesterday and got the answer I was looking for. Again, thank you for your help.


Keep in mind you are talking about a 35 year old boat, so what was there on day one, hopefully is not what is there now. Undoubtedly there have been changes, so it is good to physically check! People often add and remove thru-hulls over the years, depending on use and equipment needs.


----------

