Through Hull Replacement, Part 2: Choosing the New Bronze Hardware

The New Bronze Through-Hulls
Having removed the old through-hulls and having determined that they were no longer serviceable, the next thing I needed to do was to figure out which brand of through-hull and which brand of seacock I should use for replacement parts. The first choice I needed to make was this: Bronze or Marelon? Don Casey, This Old Boat, 2nd Edition, had good things to say about Marelon, a high-tech plastic manufactured by Forespar Marine. As you'll see in this posting and in subsequent ones, I ended up purchasing several Marelon fittings for my new plumbing system, but as far as the through-hulls and seacocks were concerned, I settled on bronze. The reason? It was simply the fact that I felt more comfortable with bronze.
Marelon Seacock
In preparing the present article, I stumbled upon an excellent article by Robb Triton on his blog, Tritonboatwork. In the two diagrams that follow, Robb illustrates how he installed backing plates in his boat to reinforce his Marelon through-hulls and seacocks.
If I were to install Marelon through-hulls and seacocks in my boat, I would follow Robb's advice. Check out his blog for the full details on how he did this.
Having settled on bronze, I next needed to decide whether to stick with flush-mounted through-hulls or transition to the mushroom-head style. The originals, as you see, were flush-mounted.
Groco, Apollo, and Buck Algonquin all manufacture mushroom-head through-hulls. Below, we see a sample of those manufactured by Groco.
I considered filling in the old chamfered, i.e., tapered, holes with epoxy, so that I could use the mushroom-head style through-hulls. The only problem was that these holes were close to the bunks of the trailer. This made me a little worried.
The hole for the galley sink waste-water was even closer to the bunk. I was concerned that a mushroom-head through-hull might come into contact with the bunk when launching or retrieving the boat. Therefore, I abandoned the idea of using this mushroom-head style through-hull.
Having decided that I would need to stick with flush-mounted through-hulls, my next decision concerned the manufacturer that I should choose. I mentioned in Part 1 (of this multi-part article) that I posted a question on the Ericson Yachts Owners Forum concerning the resizing of the holes in my boat for the installation of new flush-mounted through-hulls. In that posting, I describe how the Groco flush-mounted through-hulls were smaller, in terms of their flange, i.e., their head, when compared to the original through-hulls. If you've read that posting, you'll remember that Emerald, an Ericson Independence 31 owner, said that Buck Algonquin brand through-hulls had been a good replacement size for the original through-hulls in his Ericson 27 (back when he owned that sized boat). This was valuable information that Emerald provided to me (and to other Ericson owners for that matter). I have every reason to believe that Buck Algonquin, a Maryland company that has been in business since the 1950s, was the OEM (original equipment manufacturer) source for the Ericson 25, or at least my Ericson 25.
The original through-hulls
Above we see the original through-hulls from my boat, and below we see a picture of some present-day flush-mounted through-hulls from Buck Algonquin. The company is kind enough to provide the consumer with detailed specifications for its through-hulls on its website. These specifications corresponded exactly to the measurements I made of my original through-hulls.
Buck Algonquin Through-Hulls
If the size of these Buck Algonquin through-hulls corresponded exactly to the size of the original through-hulls, then why did I eventually settle on the Groco brand through-hulls that you see pictured below? The answer has nothing to do with the through-hulls themselves and everything to do with the seacock.
Groco Through-Hulls
I liked the sturdy bronze seacock that was sold by Buck Algonquin.
Buck Algonquin Seacock
It was somewhat similar to the Apollo brand bronze seacock that I purchased from West Marine (for the purpose of test-fitting it, before returning it to the store about one hour later). 
Apollo Seacock
It was also somewhat similar to the Groco brand seacock that was also sold in the local West Marine. All of these seacocks had one thing in common: an integrated flange at the base. This base, of course, was meant to be secured in some way to the hull to support the seacock. The standard procedure for installing all of these seacocks and the accompanying through-hulls, was first to secure the seacock to the hull and then to screw the through-hull into place from outside of the boat. Since Buck Algonquin, Apollo, and Groco all manufactured the same type of hardware, and since Buck Algonquin, from what I could tell, was the OEM source for the Ericson 25, it made sense to me to choose Buck Algonquin. That would save me the chore of having to resize the chamfered holes to accommodate the smaller Groco through-hulls.
It was around this time that I took a closer look at one of Maine Sail's articles on his website, Compass Marine. There's a link on the homepage of this Ericson 25 website, if you wish to check it out for yourself. At any rate, Maine Sail speaks of the virtues of using the Groco brand flange (together with a Groco brand inline valve) as opposed to using a seacock with an integrated flange. The idea is that by having an independent flange, you can, if necessary, remove an inline valve for inspection, cleaning, or replacement without having to remove the through-hull. Do you get what I'm saying? By having the independent flange and the through-hull as separate components from the in-line valve, you can easily remove the inline valve in the event that it becomes stubborn or faulty.
Groco Brand Flanges
As Maine Sail explains (with excellent pictures) and as the people at Groco themselves explain in the diagram below, the flange, with its NPS, i.e., straight, threads at it base is designed to correspond to the NPS threads of the through-hull. Likewise, the flange, with its NPT, i.e., tapered, threads on its top side is designed to correspond to the NPT threads of inline valves. The flange thus prevents some ignorant person from trying to screw an inline valve (with tapered threads) directly onto a through-hull (with straight threads).
This was the very thing that some benighted individual had done in the Ericson 25 that I purchased. I've touched upon this issue before in my earlier article, "Plumbing, Original," but since we're on the subject. Let's take a look at them again. Here's the raw water intake for the head. No seacock. Just an inline valve screwed onto the through-hull.
Here's the waste-water outlet for the head. Same thing. The only difference is that the guy used an elbow to join the inline valve to the through-hull.
There were only about three threads that were keeping these pieces of hardware together. We can also say that there were only about three threads keeping this boat afloat. If you're curious to know how much water a hole like this will admit into your boat in a very short period of time, check out the math that Don Casey performs in This Old Boat, 2nd Edition.
The people at Groco sum up their flange style set-up quite nicely in the picture below.
So . . . I settled on this flange style set-up. Now some readers might be wondering why I, despite my commitment to this style, would not simply substitute the Groco brand through-hull for the Buck Algonquin brand through-hull. After all, the Buck Algonquin through-hulls, with their NPS (straight) threads would be compatible with the NPS (straight) threads of the Groco flange, wouldn't they? Yes, they would, but despite the fact that they would be compatible in terms of their threads, I could not be entirely sure that they would be compatible in terms of their size. Specifically, I wanted to know if the bronze bolts, which would secure the flange to the hull, would be obstructed by the head of the through-hulls. Remember that the heads on the Buck Algonquin through-hulls are larger. This means that the heads of these through-hulls might have prevented me from passing bolts through the flange and thus through the hull.

If you're having trouble picturing what I'm talking about, take a look at the picture below of the raw water intake for the head. Here we see the bronze bolts that are securing the Groco flange (inside of the boat) to the hull. By this point, of course, I have resized the old chamfered hole to accommodate the new Groco through-hull. There is not a lot of space to play with here.
The space was even tighter for the waste outlet through-hull.
The point is this - that I could not be absolutely sure that the Buck Algonquin through-hulls would have worked with the Groco flanges without having both pieces of hardware in my hands. Sure, I could have used my original through-hulls (which appeared to have been manufactured by Buck Algonquin) as references, but it would have been better to have the brand new versions in my hands.
The original through-hulls
The Groco hardware was readily available at the local West Marine, and, at this time, West Marine was still price-matching. The bottom line was that I was able to get all the Groco hardware I needed for a rock bottom price, so this was the brand that I purchased. Knowing what I know now (i.e., how much of a pain it can be to resize chamfered holes), and being given the opportunity to do it all over again, I might just opt for the Buck Algonquin hardware, i.e., the Buck Algonquin through-hulls and the Buck Algonquin seacocks.
Buck Algonquin Through-Hulls
Buck Algonquin Seacock
Yes, opting for Buck Algonquin would have saved me a lot of time, at least initially. The benefit, of course, of all the work I did to install the Groco hardware is that I can easily replace the in-line valves, if I ever need to, without having to remove the through-hulls from the boat. All this work will only pay off, if I keep the boat for the long time. Given all the work I've done on her, I think, at this point, that I will.

On the subject of inline valves, let's now talk briefly about the choice I made in terms of what are known as "full-flow" valves and fittings. Groco's inline valves are called "full-flow," presumably in reference to the full-flow fittings (as opposed to the "standard-flow" fittings) that you can opt to purchase for use with the full-flow inline valves. Confused? Read on.
Groco, Full Flow, Inline Valve
Let's use the 1.25 inch full-flow, inline valve that I had to purchase for the waste outlet through-hull as an example. This valve accepts either a standard-flow fitting or a full-flow fitting. Take a look at the standard-flow fitting below. It's probably a .75 inch fitting, but never mind the size of the fitting in the picture. Pay attention to the shape of the fitting. Notice how the barbed end is smaller than the threaded end? On the 1.25 inch standard-flow fitting, the barbed end is made to accommodate a hose that is 1.25 inches ID (Internal Dimension). So what's the problem, you might ask? Well, that barbed end itself has an internal dimension, and on the 1.25 inch standard-flow fitting that barbed end ID is just 1 inch. That means that this portion of the plumbing will be .25 inches smaller than the through-hull, the inline valve, and the hose, all of which are 1.25 inches.

Now let's take a look at the full-flow fitting. The 1.25 inch full-flow fitting has a barb that is designed to accept a hose that is 1.5 inches ID. This means that the barb itself has an ID of 1.25 inches. This, of course, is the ID of the rest of the hardware - the full-flow inline valve, the independent flange, and the through-hull. This consistency is what allows these pieces of hardware together to be "full-flow."
Below we see the 1.25 inch flange, the 1.25 inch full-flow inline valve, and the 1.25 inch full-flow fitting that I purchased for my boat.
Now some of you might be wondering why I purchased 1.25 inch hardware for the waste outlet when the standard size is 1.5 inch. You might be wondering why (especially if I was going to have to resize the holes to accommodate the Groco brand hardware), I would not go ahead and resize the waste outlet to accept 1.5 inch hardware. Well, on the one hand, I figured that this would make an already challenging project more challenging; on the other hand, I also realized that any standard system, with 1.5 inch hardware, would have its own share of 1.25 inch bottlenecks. What do I mean by this? Please follow along for just a little bit longer.

The standard size sanitation hose is 1.5 inch ID. Many people opt for Shields brand hose. I opted for Trident, for reasons I will address later.
Trident 101 Sani Shield Hose
As I explained above, the Groco full-flow 1.25 inch fitting allows you to use the standard 1.5 inch ID hose. Even with this full-flow fitting, all the bronze hardware in this part of the system, as I suggested, is a bottleneck of sort. There are others, however. Let's start with the head proper, i.e., the toilet, and work from there back to the through-hull.

The toilet presents a bottleneck in anyone's system with standard 1.5 inch ID hose. Why? The same reason as elsewhere. The 1.5 inch ID hose has to be joined to a barb that is 1.5 inch OD and thus 1.25 inch ID. Below we see the original toilet in my boat. I replaced this Raritan PHI with the current model, the PHII. Regardless of the make or model, the barb is the same: 1.25 inch ID.
Next, there is the holding tank, an important part of any plumbing system, one that few mariners do without these days. If you pump the waste from your toilet into your holding tank, that waste in the 1.5 inch ID hose will have to pass through a 1.25 inch ID fitting on the holding tank. Likewise, when it comes time to pump out your waste from the holding tank, the waste will again have to pass through a 1.25 inch ID fitting to enter the 1.5 inch ID hose that leads to the pump. Below we see a drawing of the Dometic Sealand 11 gallon vertical holding tank, the type that I used for my system.
The pump itself, likewise, has 1.25 inch ID barbs on both sides to accommodate the 1.5 inch ID hose. These two barbs are two more bottlenecks in the system.
Finally, there is the vented anti-siphon loop (at least for those wise enough to use one). The ID (Internal Dimension) of any anti-siphon loop that will accommodate a 1.5 inch ID hose is 1.25 inches. Thus, this vented anti-siphon loop, with 1.25 inch ID barbs on either side presents two more bottlenecks in anyone's system, even if he has a 1.5 inch ID through-hull, flange, inline valve, and fitting.
Therefore, my decision to stick with the original 1.25 inch through-hull (and use the Groco full-flow hardware along with it, was not a careless one. If you are interested in reading some of my earlier (and less fully developed) thoughts on this, see the thread I initiated on the Cruisers Forum: "1-1/4 Inch Waste Outlet Through-Hull."

When it came to choosing the fittings for the other two inline valves, both of which were .75 inches ID, I did not opt for the full-flow fittings, but instead purchased those that are classified as standard-flow. The reason? The barb for the standard-flow fittings accepts hose that is .75 inches ID. Since the standard size hose for the raw-water intake for the head is .75 inches ID, and since the standard size hose for the galley sink drain is .75 inches ID, there was no reason for me to purchase full-flow fittings for these inline valves. Below we see the .75 inch flange, and .75 inch inline valve, and the .75 inch standard-flow fitting that I purchased for the raw-water intake for the head. As far as the fitting itself was concerned, I opted for the 90 degree angle fitting, since this provided me with the most sensible means of routing the hose around the toilet. The reason why this was the most sensible decision will become clear in subsequent postings.
This ends Part 2 of my multi-part article on the steps I took to replace the through-hulls on Oystercatcher, my Ericson 25.

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