Marelon Ball Valves

[DJW]

I will be replacing 3 order 3/4 inch sea cocks with 3 new Marelon ball valves and new Bronze thru-hulls on our Cascade 42 during our haul out in January. Do I need to put Teflon tape on the thru-hull threads before I screw the new Marelon ball valves on?



Dennis

 

[ITMaster]

If you are interested

In doing it the right way, everything you could want to know is to be here:

http://www.pbase.com/mainecruising/replacing_thruhulls

I think you will have a good job well done if you follow his process

Good luck

 

[Maine Sail]

Please be very careful attempting this. The expansion and contraction coefficients are quite different for Marelon & bronze. Threading a female Marelon ball valve onto a male thru-hull made of bronze can result in a splt Marelon valve.

If you were threading a male Marelon fitting into a female bronze fitting it would be safer than a female Marelon onto a male bronze.

Also NPS to NPS is not a mechanical watertight seal like an NPT to NPT thread is. When installing a Forespar valve onto a thru-hull you will have NPS to NPS and this seal is 100% reliant on pipe dope, tape or both for a seal seeing as they are both straight non tapered threads. NPS to NPS is NOT used in the plumbing or pipe fitting trade for sealing and it is my opinion that it should not be used below water either but to each his own.


Either go all bronze or all Marelon. It is not generally a good idea to mix plastics and bronze bellow the waterline especially when the plastic is the female piece..

While Marelon is inert to galvanic corrosion you have added zero benefit to the equation by using a Marelon BV. Your weak galvanic link is still the bronze thru-hull. Marelon also requires yearly lubing and MUST be excersized on a regular basis or they will freeze and you'll snap the handles. Just ask around I know of many who have had this happen inclung myself and other members of this forum..

It is also a very good idea to, at a minimum and if you absolutely must used a non-flanged thru-hull with a valve on it, that you remove and re-bed them prior to replacing the valves. Many times just the action of removing an old valve from the thru-hull will break or damage the existing 10, 15, 20, 25 or even 30 year old seal...

P.S. Anytime a valve is threaded together that uses NPT threads as a seal it should be teflon taped and then pipe doped as well. Most professional pipe fitters use tape and dope together not one or the other. Again I personally would never install NPS to NPS below the water line, with out some orther means of sealing like a proper flanged / bolted seacock but some do and feel comfortable with it..

 

[Rich (P303)]

I will be replacing 3 order 3/4 inch sea cocks with 3 new Marelon ball valves and new Bronze thru-hulls on our Cascade 42 during our haul out in January. Do I need to put Teflon tape on the thru-hull threads before I screw the new Marelon ball valves on?



Dennis

I would keep it all bronze... I think the price difference would be minimal.

 

[sailingdog]

Instead of using Marelon ball valves on the Bronze through hulls, I'd highly recommend you use Forespar's all-Marelon Through-hull with intergrated ball valve or go all bronze. Listen to Maine Sail's advice as well.

If you aren't going to maintain the ball valves with regular exercise and annual lubing, go with all bronze, cause the Marelon WILL FAIL.

 

[Ed Schenck]

Why ball valves?

Do I understand the original question, that you are replacing seacocks with plastic ball valves. Why? If the thru-hulls and/or seacocks are corroded and you are replacing the thru-hulls then why not install new seacocks? I guess I am missing something.

 

[Rick D]

Marelon's Guide For Use With Bronze Trru-hulls

...you can install Marelon on bronze but there are some important conditions. See the link:
http://www.forespar.com/MarelonPlumbing/marelonTechTips.shtml

 

[Maine Sail]

...you can install Marelon on bronze but there are some important conditions. See the link:
http://www.forespar.com/MarelonPlumbing/marelonTechTips.shtml

I always loved their tips section:

"*Be sure the bronze thru-hull is sound" = Very good advice!

"*Be sure the threads are clean and all old sealant is removed" = Very good advice!

"*Do not cross-thread! Bronze will "cut" threads if forced onto Marelon®" = They're not kidding Marelon will cross thread quite easily!!

"*Use adequate Teflon® pipe tape or plumber’s dope for thread sealant" = They grossly under state this point an NPS to NPS seal is not intended to be a pressure seal as NPT to NPT is. The safety of your vessel, in keeping your boat above water with NPS to NPS, is twenty cents woth of Teflon tape and not a mechanical seal as you'd get with NPT to NPT, a flanged thru-hull or flanged adapter plate..

"*Be sure you do not "violate" the sealant on the thru-hull by twisting in the hull." = As I mentioned above it would be best to replace them or re-bed them entirely when ever you change a valve. The OP plans on going new so I would advise Proper flanged seacocks not a valve on a thru-hull...

"*Do not over-tighten the valve. "Hand tight" is all that is needed" = This is primarily because NPS to NPS threads never "tighten" down on one another like NPT to NPT do. NPS to NPS is just like a nut and a bolt thread in that it will bottom out before it actually self seals as it can never 100% self seal and relys on teflon tape or pipe dope but preferably both, to keep the water out. Hand tight below the waterline IMHO is a questionable practice but to each his/her own. The simple act of opening and closing a "hand tight" valve can move it and break the seal that is keeping water out of your boat. Over tightening of a Marelon valve onto a bronze thru-hull can lead to a failure of the Marelon valve. This has been brought up on a few of the sailing forums over the years. While rare it can and has happened.

"*Properly bond or ground the bronze thru-hull. It is still subject to electrolysis and corrosion, even with the Marelon® valve installed" = They are pointing out the obvious here and adding a Marelon valve to a bronze thru-hull does not avoid the potential for galvanic corrosion.

"*For the "Ultimate" in corrosion control and weight savings, change all thru-hulls to Marelon® as well as the valves!" = As many have already stated it's a good idea to use all Marelon or all bronze. Forespar simply wants to sell the uninitiated and under educated (around the subject of thru-hulls/seacocks) boater more valves to slap onto old thru-hulls as a quick fix. I don't blame them as they are in the business of making money but I do question the application and their blatant use of warnings and disclaimers such as the one below that nullify what had previously been said...

"Note: There are a number of foreign-made bronze thru-hulls on the market. Forespar® cannot guarantee thread compatibility on these inferior thru-hulls." = This is their disclaimer that clearly waives any liability when you mix bronze thru-hulls with Marelon valves. Just try to find any thru hull today, even by American manufacturers, that is not cast and machined off shore. last time I checked the Groco's and Perko's are cast off shore and could clearly fall under the "disclaimer"..


"Even some new production boat builders are installing our Marelon Integrated valves on bronze and stainless steel thru-hulls as standard equipment. High quality blue-water fishing boat builders such as Grady-White Boats are using Forespar® Marelon® "93" series Integrated valve systems on bronze thru-hulls without any trouble." = The key words are "SOME" and "PRODUCTION BOAT BUILDERS". Any builder slapping valves directly onto thru-hulls is cutting a corner! If you notice Forespar does not make the same claim they did in the second sentence about Grady White being a "quality builder". I'm sure this was not by accidednt and I would guess they don't feel that a builder slapping a BV onto a thru-hull is "quality" work. Grady uses a flanged Series 93 valve not a BV on a thru-hull. Even Catalina uses the Series 93 valve which has a flange. Quality builders such as Morris or Hinckley use flanged and bolted seacocks as do many other "quality" builders.

 

[Roger Long]

Again I personally would never install NPS to NPS below the water line, with out some orther means of sealing like a proper flanged / bolted seacock but some do and feel comfortable with it..

I'm one of those on a limited basis. I wrote a whole blog piece, complete with illlustrations of threads, on why it was a bad idea and the yard service manager then said he had been replacing gate valves with NTP ball valves on NPS through hulls for 20 years and never heard of a problem. I put a trial fitting on one of the through hulls I took out and determined that the threads are closer and the material more flexible than you would think.

I never heard myself of tape and dope together but there is a lot of difference between domestic water pressure and hammer and the low pressure of most through hulls.

I would NOT use ball valves on through hulls anywhere were heavy items stored or someone's foot could hit them or on large diameter fittings like cockpit scuppers. I have just three thru hulls in my boat. Two are ball valves on old through hulls and they are under the head sink and small diameter.

I went to a lot of trouble to reduce the number of seacocks in my boat. I'm also more comfortable with simply capping unused through hulls with bronze caps than pulling them out and having a large fiberglass structural repairs with secondary bonds.

You can see how I got rid of my cockpit drain seacocks here:

http://home.roadrunner.com/~rlma/Strider.htm

All hotel drains go to the bilge sump on my boat and are then pumped overboard from there. I do not believe in trying to drain stuff below water level by gravity. Any floating stuff that goes down ends up floating as a little raft at the salt water level and then picking up more stuff until you have a clog. These are the kinds of drains that are also often on places you may forget to think about when you see water over the floorboards.