Hi to all: Next week "Moments of Clarity" will be taken out of the water for a couple of months and this time I'll be replacing all the thru-hulls and seacocks. I've gathered a lot of info over the net and, apparently, the proper way to do it is to buy seacocks that can be thru-bolted to the hull or at least screwed onto a plywood backing plate. That way the seacock itself can never be unscrewed by accident and the whole structure is more solid. The most common practice though--which is also the case with my boat--is to screw an in-line ball valve on the thru-hull which you have previously (and preferably) tightened on a backing pad. Has anybody gone through the process and what is your experience? -Nicholas Moments of Clarity #334  | Nicholas,
When my son purchased his Ballad about seven years ago, replacing gate valve
seacocks was one of the first jobs on the never ending list of things to
do...insurance regulations required ball valves. We bedded and fiberglassed
marine plywood discs to the hull, to which the seacocks are then securely
bolted. The stainless bolts were epoxy "locked" into the assembly. Think
we coated the wood all around with penetrating epoxy, before applying to the
hull. Tight spaces are the only complication I can remember.
Regards,
Pentti Nikkanen
THALASSA - #194
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 | A proper flanged seacok is the best solution because the threads are compatable with the thru hull fittings. Ball valves typically have tapered threads which do not engage well with the straight threads on your thru hulls. Have a knowledgable pipe fitter help with matching your fittings. Best Regards, Tony Allport Peiades, #191 |
 | I just installed a couple of these guys, made out of brass, I believe. I know it's not the best possible, I believe stainless steel or bronze could be better, but it쨈s still recommended and sold here in Denmark a lot, considered good quality, and easily available. The ball valve shuts and opens real easy. I wish I knew more about the subject, but haven't taken the time. They were easy to install, packed with flax and this clay like substance, and easy to operate. I don't expect to have problems with them. But I do know they wont last forever. Jesper M. |
| Ooops, I didn't pack the flange against the hull with flax and clay, only the parts with each other. I packed the flange against the hull with SikaFlex I believe, one of the modern silicone products. Jesper M. |
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Hi Jesper,
As you point out, brass is not the best material for seacocks, but you must be aware that, as brass is an alloy of copper and zinc, your seacocks will be subject to galvanic corrosion the moment they come into contact with seawater.
As long as you are aware of this you have some protection, but it is considered in the UK to be very unwise to use brass fittings where, if they fail, the boat will sink.
I actually saw a boat in one of my local boatyards that had had brass seacocks fitted, and after only three years, one of them had shattered! Yes shattered! Fortunately this occurred in the yard as the owner was trying to free the seized seacock.
It seems that the zinc in the alloy had corroded away, leaving only a honeycomb of copper behind, which was very brittle, and when the guy tapped the fitting with a mallet the fitting disintegrated. This I believe, is not an uncommon occurrence with brass seacocks.
I am also told that bonding brass seacocks to a sacrificial anode is pointless, as the zinc in the anode will not necessarily corrode before the zinc in the brass.
It is always a good precaution to tie wooden cone shaped bungs of the right size to every through hull fitting, so that if a fitting does fail, and you are on board, you can immediately force the bung into the hole.
There are many "plastic" fittings available, but never use ABS, PVC or polycarbonate fittings. I believe the only approved "plastic", which has passed the same tests applied to bronze for use below the waterline is "Marelon", a fibreglass-reinforced nylon.
Tim
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 | Thank you all for your replies. From what I know, Tim is right regarding brass hardware for marine use. Marine bronze or Marelon are recommended. Unfortunately, in Greece virtually all chandlers market ball valves instead of proper seacocks. Of course, some brands are better--and more expensive--than others. I'm enclosing a couple of photos of proper marine seacocks plus an article from Don Casey on proper installation. They put to shame the installations on most boats. Unfortunately, to my knowledge, the pictured seacocks aren't available in Europe and one has to order them from the U.S., with prohibitive import duty in Greece. It seems that my only viable option is to buy the best quality ball valves I can find and install them on bedded plywood pads. Luckily, in Ballads all the thru-hulls are located where they can't be stepped or have a weight dropped on. In the coming months, I'll let you know how this project goes. Nicholas, Moments of Clarity #334 Attachment: Installing a Seacock.doc |
| The "Installing a seacock" by Don Casey, contradicts my perception of good craftsmanship in three ways. He suggest that the hull-through should screwed in place after applying the sealant. I was told not to let the hullthrough rotate on the sealant, while tightening it from the inside. He also suggests the use of plywood as a washer under the inside part of the arrangement. What a poor choise of material, when the rest of the arrangement is made out of GRP and Metal. Finally he suggests using the sealant to seal the threads with. I either use the flax (danish: pakgarn af hør) with the appropriate clay, or a plastic tape made for the purpose. Sealing threads with some sort of sealer does not sound right in my ears. Also I find the use of the valve as part of the fastening of the hullthrough to be unfortunate. My hullthroughs (some of them seem to be original) are all fastened by them selves, and the valves are then mounted later, and may be removed without removing the the hullthrough. and I don't like the extra three little holes. It is a very complicated solution I think. Too many nuts too much plywood. I used a sealant that also glues. I am confident it will keep my throughhull from rotating when the valve is mounted, or realigned. I don't mind overdoing things a little to be on the safe side, but what happens (not if, but) when the plywood ruts away? Jesper. |
| Hi Jesper: I take it that the whole concept behind seacocks is that they become part of the hull structure. Ball valves, on the other hand, are simply threaded on a through-hull. In America, ABYC (American Boat and Yacht Council) suggests that any through-hull arrangement should withstand a 500-pound weight for 30 seconds. Naturally, a seacock that’s bolted on will fare better than a threaded ball valve. It may not be the case with the Ballad, but if, for example, while trying to lift a scuba tank from a locker, you drop it on your engine water seacock, well…you see my point. I agree with you that the plywood pad will rot if left uncoated. Apparently the article forgot to mention that the pad should be either glassed in or coated with epoxy thoroughly (all other articles on this process that Iâve read mention this). Also, you’re right in not letting the through-hull rotate when you tighten the nut from the inside. That’s true when you’re installing ball valves. With seacocks, however, the process is reversed. First you mount the seacock on the hull and then you tighten the through-hull from the outside. Also, it’s good practice to let the sealant cure for several hours; otherwise if you tighten immediately after you apply it, you’ll squeeze it out. Some elasticity is good since a hull flexes when sailing and over-tightened through-hulls create hard spots (I have stress cracks around all my through-hulls because some idiot over-tightened them in a previous installation: see photo). Regarding using sealant on the threads, opinions differ. Like you, I’ve used teflon tape on the threads, which is quite common. Others use sealants (like Sikaflex) which also makes sense to me as it is entirely appropriate for below-the-waterline use. Nicholas Moments of Clarity #334 
A reminder not to over-tighten through-hulls |
| There is a lot more to seacocks, valves and through hulls, than imagined. The idea that a through hull has to be strong in case something rests or fall on it, is important of course. The apllying of epoxy or varnish to the plywood was not omitted. it just wont protect the plywood for ever, if submerged in water in the bilge for example. Jesper. |
 | I had a wee stopcock disaster the other day. I was working on my boat, forgot I had opened the little hatch down into the keel and walking through the cabin one of my feet went down the hole accompanied by a bang and then the feeling of cold water running against my ankle. I had broken the engine water stopcock clean off. The next day after slipping the boat and having my boat guy replace the through hull fitting and stopcock (plastic) I could see the funny side of it. I note that one of the posters here said to make sure there are wooden cone shaped bungs attached to each fitting. I would also add make sure they actually fit the hole. In my case the smallest tapered bung I had was larger then the hole so I had to whittle it down to make it fit which was OK at the wharf but would he been a problem at sea. |
| Hi to all: Moments of Clarity is coming out of the water next Friday. (The beginning of summer may seem like a strange time for a haul-out, but the hull dries out much better and one can work more comfortably.) Anyway, while I've been looking into various seacock configurations, a book that I've been re-reading made me consider reducing the number of below-the-waterline through-hulls as well. In their Cruising Encyclopaedia, Steve and Linda Dashew describe how they manage with 2 or 3 through-hulls in their 70+ foot boats. They do it by manifolding one through-hull to various outlets. Although, obviously, they have a lot more space to play with than our 30-footers, I have a vague concept of how I can turn the 5 through-hulls of Moments of Clarity into 2 or 3 as well. I won't divulge anything right now but, hopefully, I'll be able to post a complete note by the end of June. John Cotton's incident highlights the importance of careful installation of seacocks, plus access to appropriately-sized softwood plugs (most chandlers sell a pack that fit all common through-hull sizes). Personally,my 46.5-size foot would probably be wedged in that space before reaching the engine water seacock but still... Also, does anyone have a toilet discharge outlet above the waterline? Nicholas Moments of Clarity # 334 |
 | Saw an advertisement for a safety valve that can be used in conjunction with a seacock, though not for the engine cooler water seacock on a Ballad. http://www.x-tight.com/ Charles |
 | Groco has a good technical bulletin on installing thru hulls and sea cocks. I just re-did all mine (Albin Vega .... I'm a Ballad 'lurker' :-). Hope this helps. Peter. |
 | Hi, having just completed a mast step repair job I now want to check/ replace the sea cocks. The current sea cocks are, I thing originals and are recessed into the hull and are flush with the outside of the hull. My questions are as follows- 1)Are these originals bronze and how will I know ?(rather than being Brass) 2) how will I know if they are degraded and need replacing 3) how do I remove them if necessary and finally are there standard replacements or will I need to get replacements machined to fit or would it be stronger to build up the recesses in the hull and use the standard ,off the shelf, fittings with the convex external flange Misstress6 |
| Bronze should be an alloy of copper and tin. There are dozens of variations with traces of other elements as well. It is hard to tell what specific alloy you have without laboratory analysis. Brass on the other hand is a mixture of copper and zinc. It has many varieties as well but is generally less durable in a marine environment because the zinc leaches out leaving the copper in a weakened condition. To complicate matters more, some bronzes also contain zinc. Manganese bronze in particular, which many propellors are made of, contains enough zinc to technicaly be classified as a brass despite its name. The most obvious indicator of a copper alloy's conditon is its color. When scratched or polished it should have a bright yellow or golden color. If it appears pink or red that indicates residual copper left behind as the zinc is used up. If your through hulls have lasted this long they are almost certainly a better grade of bronze but it never hurts to examine them closely. Tony Allport Pleiades #191 |
| Hi Tony, thanks for a short simple explanation. I appreciate that. Copper and Zink is not as good as copper and tin, because zink, like in an anode, can be electrically removed. And the test s to take some very fine sandpaper, sand the through hull a little and observe the color which if it is like gold, is good, if it is reddish, it is not so good. Is this a correct simplyfication? Jesper Milling |
| Hi Misstress6: I changed all my through-hulls and seacocks a few months ago and I've posted a relevant note in the "Accommodation" section named "General plumbing+holding tank". Usually, recessed through-hulls are used on racing boats in order to create a smooth underwater profile which, I suspect, was the reason why they were originally installed in Ballads. I've gone for the normal mushroom-shaped through-hulls, since racing isn't really my goal and they're easier to install. Since I was planning to replace all through-hulls and seacocks, removing the old ones was easy: from the inside of the boat, I cut the threaded part off with a grinder and then carefully used the grinder (again) to split the nut. The remainig through hull simply fell off the boat. I would encourage you to epoxy or laminate plywood discs where you install the new through-hulls/seacocks and reduce their number if you can. My boat came with 5 originally and now I've 3. (I could have made them 2 but I couldn't find a way to bring the sink through-hull above the waterline without using a pump.) I chose Marelon products--the only synthetic seacocks approved for below-the-waterine use. Marine bronze (Groco, etc) would also be great but they were too expensive and complicated to import to Greece from the US. If you need more or clearer photos, let me know. Nicholas Moments of Clarity #334 |
| I'm about to have all my underwater seacocks replaced and my boat-builder ("underwater" is synonymous to "too risky" to me, so I'm leaving this job to an expert) recommends stainless stell - stay away from brass, he says, modern brass seacocks are rubbish. Does anyone have an opinion on stainless steel? It doesn't seem to figure in this chain of messages. |
| Hi Charles: Stainless steel was the other option I considered and it has a lot of merit. Vetus markets stainless steel seacocks and when I checked them out at the local dealer they seemed to be well-engineered. More importantly, they're made of 316 grade which is the best for marine use (avoid any other grades, like 304 etc). Surprisingly, they are also very affordable. Take a look at http://www.vetus.nl/en/catalogue_2008.html It's worth laminating a plywood backing plate on the hull, at least on the toilet's discharge seacock. At 1 1/2 inches (38mm), it's quite big and heavy and the hull in that area is quite thin (10-11mm). Although you can't really step on the seacock by accident, it's good for peace of mind. Nicholas Moments of Clarity #334 |
| In general, stainless steel is not recommended for use below the waterline. The reason is that its resistance to corrosion depends on the formation of a thin film of chromium oxide on its surface. This film forms almost immediately when stainless steel is exposed to oxygen in the air. If it is submerged or wrapped in a damp packing material like dirt, rags, or a failed sealant, the film will tend to breakdown due to insufficient oxygen. Without this layer of chromium oxide on its surface stainless steel may corrode very easily. It usually takes the form of crevice corrossion which starts as pitting on the surface and can eventualy eat deep into the steel. The narrrow pits and crevices tend to retain moisture and maintain a low oxygen environment which in turn perpetuates the corrosion. The surface of the stainless steel often shows little more than a pin hole where the corrosion started. As with other alloys there are dozens if not hundreds of varieties of stainless steel. Some are excellent and others are not. But they all rely on this same process for their durability. Stainless steel propeller shafts tend to be of very high quality alloy, but even they are known to pit inside the cutless bearing if left idle for too long. On my Ballad I replaced two badly pitted stainless steel bolts from the fitting at the bottom of the skeg which holds the rudder. I have also found pitting on the bolts holding the life line stanchion bases to the deck. In my job as a marine surveyor I recommend genuine bronze or Maralon fittings be used below the waterline. Tony Allport Pleiades #191 |
| Scary stuff! I've no expertise, but Maralon gives me an impression of plastic and the fear that it will become brittle. Isn't this a concern? Charles |
| Maralon is made of nylon impregnated with fiberglass, it is always black as far as I know. It has proven to be very durable unlike the white plastic fitting commonly seen above the waterline. My one complaint is that the action of the valve tends to get very stiff with age, so it does need regular maintenance and lubrication. Tony Allport Pleiades #191 |
| Tony indeed makes a strong point against the use of stainless below the waterline and I can't argue with the opinion of a marine surveyor. I was aware about the pitting problems but it hadn't occurred to me that it also applied to through-hulls and seacocks, so in retrospect, I'm glad I didn't choose stainless after all. According to my research, bronze seacocks are the best choice but the difficulty of locating/importing the right ones was too much for me. About a year ago, I contacted Groco in the U.S., a company that makes excellent marine bronze hardware and they were willing to send me through-hulls and seacocks but at too high a price (not their fault, it was the shipping charges that were high). Since underwater fittings are of primary importance in boats, maybe one should bite the bullet and pay up. At any rate, their website is www.groco.net and it's worth checking out. Another company that makes excellent marine bronze hardware is Blakes in the UK. They only market 3/4 and 1 1/2 inch fittings (19mm and 38mm) but these are the most popular sizes for engine & toilet intake and toilet discharge anyway. Take a look at http://www.blakes-lavac-taylors.co.uk/blakes_seacocks.htm Again, they're not cheap. As far as Marelon through-hulls and seacocks go, Tony is right in that they need to by actuated regularly. In all the forums that I've read on the internet, the only reason people had problems with Marelon fittings (primarily, handles breaking) was that they had become stiff from lack of use. Since I'm at the boat almost every weekend (and I'm anal about this, anyway) I always make sure to open and close them several times. According, to Steve and Linda Dashew--custom builders of high-end aluminium sailboats in the US, the only other problems with Marelon fittings are that they will melt in a fire and they may also be hard to operate in arctic conditions. At any rate, they install Marelon in all their boats and if you see their Sundeer and Deerfoot designs you'll realise that they don't do it to cut costs. Of course, the fact that Marelon is corrosion-free--a great plus in aluminium boats--helps too. Also, to clarify one thing: Marelon seacocks are black, while Marelon through-hulls are white. However, the through-hulls are easy to distinguish from other, cheap plastic varieties, as they're thick-walled and appear very robust. For more info, check out www.forespar.com Marelon fittings are readily available in Europe. In the UK, you can contact www.improducts.co.uk -Nicholas |
| Hi, after two boats sinking on their moorings due to failure of seacocks/valves and I am about to review mine, I follow with interest. I will be tackling these following a galley makeover 1) Are there any issues with using Bronze skin fittings with internal Stailless steel(316) valves? 2)I have noted comments about reducing the number of through hull holes by combining and manifolding. Any details/photos |
| Hi misstress6: From what I know, it is unwise to mix through-hulls and valves made from different materials or, indeed, metals . Each metal has a different position on the galvanic scale, some being more noble than others. I don't know the exact ranking of bronze and stainless but, as Tony has pointed out, you'll have to know what sort of bronze it is, etc. Also, never combine synthetic through-hulls with metal valves and vice versa, as the two materials have different expansion rates, i.e. they react differently to temperature changes. What material you go for is up to you. Both synthetic and bronze have merits and are safe if you take into considerations their characteristics. At any rate, you may find it easier to install all new parts. In my boat, the valves were impossible to unscrew from the through-hulls, so I just cut the whole thing off. Believe me, installing through-hull hardware isn't difficult at all; like anything, it simply needs a thorough approach. As for reducing the number of through-hulls, let's assume that you have five of them already: 1.Engine intake 2.Toilet intake 3.Toilet discharge 4.Sink 5.Saltwater foot pump What I did was to combine all saltwater intake needs into one through-hull, while having another one for the toilet disharge and a third one for the sink. When you open the photo links below, you'll see that I got rid of the footpump altogether, so the saltwater intake serves only the toilet and the engine. In doing so, I removed and plugged the original engine intake that was in the bilge and enlarged the hole that was for the footpump under the sink in order to fit a 3/4 inch (19mm) through-hull/valve rather than the original 1/2 inch (13mm). This works great since both toilet and engine intakes are 3/4 inch (19mm). Also, the through-hull is now much closer to the engine and, although it's a greater distance from the toilet, the hand pumping effort is the same. (If the footpump or another saltwater pump needs to be installed in the future, the same throughhull can be used via another manifold.) Technically you can reduce the number of through-hulls even further by emptying the sink above the waterline with the use of a pump. Even the toilet discharge can be taken above the waterline but that's probably an overkill and especially difficult to do given the Ballad's size and freeboard. Obviously, since any manifold increases the number of joints, you have to be careful and use double jubillee clips where required, good-quality hoses, teflon tape, etc, but it sure is worth the little extra effort in order to have peace of mind. My system was pronounced leak-proof from the start. If you can't open the links below, let me know. -Nicholas http://picasaweb.google.gr/patentnick334/ThroughHulls/photo#5159066861629621442 http://picasaweb.google.gr/patentnick334/ThroughHulls/photo#5159066895989359826 |
| Many thanks for photos and info - oh what lovely clean and pristine bilges you have !! . Ps what material is the T piece, are the valves and skin fittnig 1 piece or seperate ? Brendan |
| Hi Brendan: The T-piece is made of bronze but you can use plastic, if you don't install an isolation valve. The body of the seacock is flanged which allows it to be either screwed or through-bolted onto the hull. After that, the skin fitting is screwed on from the outside. This is the reverse process of when installing conventional seacocks. I find it more secure. In the "Accommodation" section you'll find a note "General plumbing+holding tank" which has a few photos of the kind of seacocks I used. The one for the toilet discharge looks huge but the smaller ones are of the exact same design. Obviously, installing new underwater hardware gave me the chance to paint the inside of the hull--it was spot-painted in the past and looked awful. Nicholas Moments of Clarity #334 |
| Hi Nicholas, Tony, I have just tracked down Marelon seacocks and am about to copy you replace the seacocks and reduce the number of thru hull fittings, however(isnt there always an however!!) would it not be more secure to thru bolt the flange thru hull, backing plate and valve rather than bolting the valve flange to backing plate ,epoxying to hull and relying on the skinfitting for locking in place ? Also what is the correct method for blocking off / filling the old holes in hull from removed seacocks and other thru hull fittings ? Brendan |
| Hi Brendan: The method you describe is the proper one. However, I didn't fancy drilling three extra holes per seacock. At any rate, the threaded thru-hull is bedded in with Sikaflex and it's impossible for it to get unscrewed by accident. Even if it did, no water would come into the boat since the body of the seacock is bolted onto an epoxied plywood pad. Also, the seacocks in a Ballad are placed where it's impossible to step on them--with the possible exception of the engine intake's in the bilge, which I plugged off anyway. As for the old holes, I epoxied a plywood pad from the inside, then bevelled slightly the hole from the outside and filled with an epoxy/colloidal silica mixture. For larger holes, like the toilet outlet's, you may need to bevel the edges a lot more and then use layers of fiberglass cloth. The West System manual has great illustrations of how to do this. If you live in the US, also check out Groco seacocks (www.groco.net). I would have gone for those but they were too expensive to have them shipped to Greece. If you buy the Marelon ones, remember that their handles need to be actuated frequently, otherwise they may seize and break if you force them (that was the only negative point that I read about Marelon when I did my internet search). Greasing the balls with Lanacote (another product marketed by Forespar) prevents any problems. So far, I've been very happy with my choice. Nicholas
Moments of Clarity #334 |
| Thanks Nicholas. Groco is 5k miles away! Ireland is our home Brendan |
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