# Replacing SeaCock Gate Valve with Marine Ball Valve



## saurav16 (Mar 22, 2007)

Hi,

My boat has gate valves for the freshwater intakes one for the head and the 2nd for the freshwater intake for the engine. My surveyor told me that I should replace the gate valves with Marine Ball Valves for safety. I think it will be a pain to remove the old gate valve since its flush with the floor and connected to the through hull.
My question is would it be possible to keep those gate valves in open position and just add the marine ball valve right behind it so the series goes Hull==>Gate Valve (open pos)==>Marine Ball Valve?

can you use something like this

http://www.defender.com/product.jsp?path=-1|51|106370|813148|319675&id=102487


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## jmunson2 (Sep 5, 2006)

Greetings!

Although certainly no authority on the subject, my personal opinion is that you wouldn't want to do that (from experience with plumbing for ponds/waterfeatures, etc.).

The gate valve is not as good as the ball valve. I'm willing to bet the current ABYC standards dictate the use of ball valves.

R&R with a ball valve would be a better choice.

The reason NOT to do as you suggest is that it doesn't solve the problem (if, indeed, it is a problem) the surveyor points out, and also overcomplicates things.

The KISS rule definitely applies on a boat.

Bite the bullet, and follow the surveyor's recommendation (if indeed you must) and you will be better off.

Sincerely,

/s/ Jon C. Munson II


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## T34C (Sep 14, 2006)

I unfortunately just went thru this with my fresh water intake for the engine. It really isn't as hard as it may sound to replace the whole thing. I started backing off the old gate valve and it just kept turning. Come to find out the original "thru hull" didn't have a flange on the outside and was really nothing more than a piece of bronze pipe glassed into the hull. I ended up spinning out the whole thing. ground down the inside of the hull to match the outside contour. (was 4 in. thick) Used a half round file to enlarge the hole to the desired size. Installed new thru hull with lots of 5200. After that set up I then put the ball valve on and reattached the plumbing. 

Whole thing took maybe a half day total time. Did it the week prior to the boat going in the water. No problems.


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## Gary M (May 9, 2006)

I agree you should take the gate valve out and maybe even the through hull to at least inspect it and rebed it properly. If you have a cored hull check that the opening is properly sealed.
However I assume your boat is on the hard, I would not mess with a old through hull and valve in the water. Murphy is still out there!

Gary


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## saurav16 (Mar 22, 2007)

Yeah I will be doing this repair on the hard. I guess its not too bad to do. But did if you are putting a seacock did you use wooden pieces between the seacock on the inner side of the hull? Or did you use glass?


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## T34C (Sep 14, 2006)

I was lucky in that there was already marine plywood glassed into the hull as a backing plate with LOTS of glass over it. Thats what made the hull 4 in. thick in that spot.


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## Maine Sail (Jan 6, 2003)

*If you have..*

If you have a gate valve threaded onto a through hull and the through hull does not have a flange you need to replace the whole thing. This is a commom "lazy way" of installing through hulls and is not supported by most insurance surveys and is also not ABYC or Coast Guard recommended.

The problem with buying a through hull, sticking it in the hole with 5200 then threading the nut onto it and then threading the valve, gate or ball, is this. Through hulls are what they refer to as straight thread meaning the threads are NOT tapered like the NPT threads of a gate or ball valve. In most cases you are lucky to get two or three whole turns down the threads of the through hull before it starts moving thus possibly breaking the seal. These threads are NOT meant to be threaded together. The straight threads of a through hull are meant to be threaded onto a flanged sea cock!

A seacock, the proper way of keeping water out, is a tapered valve or a ball vavle as made by either Apollo, Groco or some others who have them made by Apollo or Groco and it has a built in flange. These valves are made from silicon bronze and NOT brass! When installing these you must bolt them directly through the hull with a sufficient backing block. This does two things it gurantees a solid mount that can't be "snapped off" by a heavy item in rough weather, or by lightning and it guarantees that the through hull won't spin, breaking the seal, when you are changing the 1.5 inch odor safe hose attached to it. You are alo NOT dependant on two or three threads when trying to micky mouse a combination of straight threads and NPT threads. If you must use a threaded on ball valve Groco makes a bronze flange with male NPT threads! No one makes a through hull with NPT for a reason!!!


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## saurav16 (Mar 22, 2007)

Thanks for the post, I was wondering though the through hull with the flange has to be mounted on wood to get a level surface, and bronze screws need to be drilled through the hull right? Won't there be a leak the screws are going through the hull? Also If the wood gets wet that the ball valve is sitting on it will swell and rot so there won't be a good seal there. Should you use glass instead of wood?


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## camaraderie (May 22, 2002)

Wood (marine ply or Teak) is fine but once you have it "fitted" well to the hull form then coat it with epoxy to avoid deterioration and then bond it to your hull using 3M 4200 or the equivilent. Note that the screws into the wood are just to keep it from turning. the real strength of the application is from the compression of the screw threads.


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## Maine Sail (Jan 6, 2003)

I laminated and made a 1/2 inch thick fiberglass board onto a sheet of glass that was waxed. I then drilled 6 inch round "donuts holes" with my hole saw and drill press. These donut holes are my solid glass backing plates. Yes it's more work but it's the right way to do it. Once I had my donut holes made I roughed the interior hull surface with a brass brush on my drill and also roughed the "rough side of my donut holes. I then mixed up a batch of fiberglass "kitty hair" and installed my backing plates. I used the small hole saw guide hole to put a threaded rod through so I could tighten everything down and I'd have a perfectly aligned and smooth as glass backing plate. Once the glass was cured I went outside and with my hole saw drilled my through hull hole. 

Yes the screws go all the way through the hull but you counter sink them then apply 4200 or similar. Once that has cured for a day or two skim over the countersunk bronze bolts with West System and cabosil or 3M Blister Repair Putty. They don't leak if done correctly. On certain hulls like some Hunter's you may not have enough thickness to counter sink properly so in this case I would laminate more thickness on the inside of the hull so you can counter sink properly..


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## Maine Sail (Jan 6, 2003)

*Cam...*



camaraderie said:


> Wood (marine ply or Teak) is fine but once you have it "fitted" well to the hull form then coat it with epoxy to avoid deterioration and then bond it to your hull using 3M 4200 or the equivilent. Note that the screws into the wood are just to keep it from turning. the real strength of the application is from the compression of the screw threads.


Cam the screws on flanged sea cocks are meant to go all the way throught he hull and they are not designed to be "wood screwed" into the backing plate. The idea of a flanged through hull is that you have multiple fastening points including the through hull and the three silicon bronze machine bolts..


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## saurav16 (Mar 22, 2007)

Helekai,

I was looking at this apollo fitting

http://www.defender.com/product.jsp?path=-1|51|106370|813148|319675&id=142110

It is bronze but silver in color. Could you use a standard bronze thru hull fitting that is bronze in color?


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## Maine Sail (Jan 6, 2003)

*It looks silver but..*

The picture makes it look silver but I'm fairly sure it's bronze in color. Always use bronze srews with bronze sea cocks!


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## saurav16 (Mar 22, 2007)

Halekai,

The through hull has to be purchased as well. I was looking at mushroom style bronze ones. They have a threading and a nut that threads on. Does the seacock also screw onto the threading of the thru hull? If so are the threads standard?


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## pigslo (Nov 22, 2004)

Countersink the flathead machine screws from the outside of the hull and cover and fair with thickened epoxy. Hopefully your hull is thick enough to do this. Take advantage of being out of the water.
pigslo


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## Maine Sail (Jan 6, 2003)

saurav16 said:


> Halekai,
> 
> The through hull has to be purchased as well. I was looking at mushroom style bronze ones. They have a threading and a nut that threads on. Does the seacock also screw onto the threading of the thru hull? If so are the threads standard?


Yes you need to also buy the thru hull. It threads into the sea cock but you don't need the nut if using with a real sea cock. Depending on your hull thickness you may need to cut the through hull a bit shorter, with a hack saw, or it will bottom out in the sea cock before it's tight. Apply 4200 to the threads after the sea cock has been mounted and beded. Then thread in the through hull from the out side using a liberal amount of 4200 around the mushroom head. It's imperative that you do a dry fit to m ake sure all lines up and fits well before applying 4200... I buy all mine from Hamilton Marine. My new boat is actually on the hard and I'm doing this exact upgrade as we discuss it here. So far I have about $450.00 tied up just in bronze......


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## T34C (Sep 14, 2006)

Halekai- Since you are the local expert, can you thread the seacock on over the thruhull nut? When I threaded the ball valve onto the thru hull it threaded on pretty well, but was "stiff". (now I know why) Good thing I'm not a plummer. I'm not sure I have room for the flanged seacock (near motor mount and not much clearance.), if not is there a thread adapter to get to the type of thread on the ball valve. 

FYI, it's almost under the engine with exactly zero chance of anything ever rolling, sliding, falling, dropping, or otherwise moving into / onto it.


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## camaraderie (May 22, 2002)

Halekai...I thought he was talking about the base of the sea-cock AFTER he puts the threaded compression mount thru hull like this:








Followed by something like this.









Actually...I prefer all Marelon fittings as I find them both reliable and less prone to seizing up...and easliy un frozen.


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## sailingdog (Mar 19, 2006)

Marelon doesn't corrode either.


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## saurav16 (Mar 22, 2007)

Where do you guys order these fittings from?


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## saurav16 (Mar 22, 2007)

Also from what I see the Marelon seacocks don't have the flange base that you need to attach to the hull.

http://www.defender.com/product.jsp?path=-1|51|106370|813148|319675&id=102487


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## kjsailingSpring (Nov 8, 2005)

*Installing in the water*

Is there a relatively safe way to install these below the waterline while the boat is in the water? Probably a silly question but I'm too cheap to take the boat out but the insurance company says "get it done!"


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## sailingdog (Mar 19, 2006)

kjsailingSpring said:


> Is there a relatively safe way to install these below the waterline while the boat is in the water? Probably a silly question but I'm too cheap to take the boat out but the insurance company says "get it done!"


Good way to sink the boat...  and you won't even be covered by insurance... hmm... that's a really good idea. Haul the boat and do it properly.


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## Idiens (Jan 9, 2007)

SD is right, haul the boat. 

But if you are a diver, you could do all the work underwater (one way or another). 

Start by jamming a bung in the through-hull from the outside and see if the gate valve still works when you take the hose off it. Open it and see if the bung works. Then see if you can get the gate valve off the through-hull. Pray that the bung holds, that the through-hull doesn't turn and break its seal. Maybe you will be lucky, but keep your diving gear on, just in case.

If you are tidal waters, and are quick, you could try drying out somewhere suitable.


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## Maine Sail (Jan 6, 2003)

*Having done this job..*

On at least seven boats I can tell you with 100% certainty that there is NO safe way, diver or not, to replace a sea cock or a through hull while the boat is in the water. You probably could replace a ball valve that was threaded onto a through hull though but this is not safe in the first palce. The sea cock is designed to accept the through hull without the nut. How for instance do you clean up the hull exterior and remove all the old 5200 and apply the new 4200 to the mushroom head while under water? How do you dry fit the sea cock and the through hull to drill the bolt holes for the sea cock? How do you counter sink the holes? My drill is not water proof.....

The female end of the sea cock has the same straight threads as the through hull and is made to thread into it. You will also need a step wrench to tighten the through hulls into the sea cock after you have applied copious amounts of 4200...

 Quote:

"I'm not sure I have room for the flanged seacock (near motor mount and not much clearance.), if not is there a thread adapter to get to the type of thread on the ball valve. FYI, it's almost under the engine with exactly zero chance of anything ever rolling, sliding, falling, dropping, or otherwise moving into / onto it."

If you don't have the space you need a flanged adapter. They are the two flanges, one stainless and one bronze, pictured in the link at the top left of the larger photo. They allow you to mount the flange like a sea cock then put a 90 degree bronze elbow and a bronze ball valve. The difference between a flanged adapter and a through hull is that the flanged adapter is straight thread on the female side and NPT on the top side! Plus the flange is through bolted to the hull for safety. Hamilton Marine does stock these adapters but they are not shown in the on-line catalog. Call them they do stock them! Marine Supplies

Picture of flanged adapter for tight spaces:
Untitled Document


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## sailingdog (Mar 19, 2006)

Halekai-

Those are not really adapters but are designed for use with standpipes or manifolds IIRC..


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## Maine Sail (Jan 6, 2003)

*This page may help..*

This page may help clarify that these are indeed called adapters and are designed to be used in the manner I described above..

Flanged Adapters:


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## Maine Sail (Jan 6, 2003)

*I had a few questions..*

I had a few questions posed to me via private message and thought I give the full low down of my backing plates.

I laminated a 2 foot wide by 3 feet long fiberglass board on a sheet of waxed glass using alternating cloth and woven roving with the outer 3 layers being cloth on each side. I built it up to 5/8 of an inch thick and then used a 6 inch hole saw in my drill press to cut out the "donut hole" backing plates. I then roughed up the hull, the rough side of the backing plates and the edges with a drill and a brass brush. I like the brash brush with a drill because it leaves nice deep scars in the surface for the fiberglass to bond to.

Once everything was preped I mixed up some fiberglass "structural kitty hair" and slathered the backing plate and the hull. I then stuck a bolt through the guide hole for the hole saw and climbed out of the boat with a block of wood and a large washer, centered the backing plate in the hole before it kicked then tightened the nut and bolt to give it a solid fit. I then climbed back into the boat and had enough time to feather the edges of the structural filler to the edges of the backing plate for a nice tapered feather.

I then used Sikaflex 292 as my sealant of choice to put everything back together with..


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## sailingdog (Mar 19, 2006)

Very nice...  

I would have countersunk the fastener holes slightly, as that allows the sealant to fill in the countersink area and form an o-ring of sorts.


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## Maine Sail (Jan 6, 2003)

*S. Dog*

Look very closely at the picture with the sealant on the flange and you can see that I did countersink the holes slightly before installing the seacock. Good thinking but I was already there....


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## sailingdog (Mar 19, 2006)

Ah... I see... I normally do it on the backing plate as well, so that there is an o-ring between the plate and the flange.


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