Thru-Hull Stats

[Peggie Hall HeadMistress]

When placed slightly above the waterline the through hulls still present a risk at least half the time you’re sailing. Most sailboats are also much lower freeboard than powerboats, leaving less space to fit the sink above the waterline while still having a reasonable height sink and headroom.

Which explains why safety standards call for ALL below-waterline thru-hulls to remain closed except when in use. It used be that those same safety standards also called for putting all thru-hulls/seacocks in easily accessible locations. But when boating industry's target market demanded that boats had to be floating condos with decor trumping safety, floating condo buyers bega deeming thru-hulls/seacocks "ugly", builders took to hiding them...under the companionway steps, in settees (under a pile of stored stuff), behind drawers under berths, in the engine compartment...I can't even count the number of owners I've "met" over the years who didn't even know where their toilet intake thru-hull was! Needless to say, it's now common to talk to owners who've never closed any seacocks, even those who know where they are!

--Peggie

 

[Peggie Hall HeadMistress]

Personally, I'm more attentive to the idea of hose failure above the thruhull, so we inspect them often and change them if there is any doubt.

Good point! According an article in the BOAT/US magazine several years ago (not sure they still publish it), old or damaged hose failure on an open seacock is the most common cause of boats sinking in their slips. I learned from several top yard managers that the average working life of ANY hose is only 10 years because rubber and plastics dry out over time, becoming hard/brittle and prone to cracking and splitting. So regardless of what a hose that's even approaching 10 years old looks like, it's time to replace it.

This has turned into a very interesting thread!

--Peggie

 

[RoyS]

You should make it a habit to write the year of installation on every hose you install. Easy on white sanitation hose and clear pvc but more difficult on black hose. Last year I replaced the forty year old fresh water tank fill hose and vent hose. Those were the last of my hoses that needed replacement. I will not live long enough to have to fight that particular battle again.

 

[FastOlson]

This is something that just escapes me as to why. Powerboat sink drains are above the waterline as I see in marinas over the years, but only about one inch. They're not going to show great long ugly streaks down the side of the hull. They present minimal concern.

It became accepted practice after the builders found that they could save significant $ by putting inexpensive plastic cast thruhulls slightly above the DLW. And, as powerboats get longer with more interior plumbing, the sheer number of the thruhulls grew -- it's common to see a row of 6 or more on the side of a power cruiser. UV really brittles them and very few owners seem to understand that they need to be replaced every ten years, or changed to $$$ Marelon fittings.
And then, the bulk of the power boats are built by a few companies that cheap out on every part possible. (Sadly not unlike the big production sailboat builders, also.)

Some buyers do know where the compromises are and how to evaluate them, but the bulk of the buyers seem to neither know nor care.

 

[Ralph Johnstone]

- it's common to see a row of 6 or more on the side of a power cruiser.

I've seen the same thing on large boats sitting in the sales area of our marina with the boats out on the hard. Always ganged together. And that's only on the one side. I've oftenwondered "what the hell are they all connected to ?"

Maybe it's a vanity sort of thing. "My boats got more drains than your boat."

 

[nramsey]

Trudesign thru hulls and eliminate the concern about corrosion and exercising.

 

[Maine Sail]

Lots of info here.....

Seacocks, Strainers & Hose Clamps

 

[dLj]

Trudesign thru hulls and eliminate the concern about corrosion and exercising.

That's an opinion. Then you have to worry about polymer degradation. That's another can of worms that folks don't like to talk about...

In short - there is no free linch.

dj

 

[Plymouth Sailor]

What blows my mind is that my galley sink drain goes directly through the hull from the sink. I would imagine the reason the boat doesn’t sink (no pun intended) is because the sink is above the waterline but why in Gods name place the thru-hull below the waterline in the first place? Just drain it on the topsides!

 

[FastOlson]

What blows my mind is that my galley sink drain goes directly through the hull from the sink. I would imagine the reason the boat doesn’t sink (no pun intended) is because the sink is above the waterline but why in Gods name place the thru-hull below the waterline in the first place? Just drain it on the topsides!

It's not that simple. Freeboard is much lower for sailboats and it's not unusual for the drain on your sink to be only inches above the DWL. This should not injure your mind. Just be sure that there is a proper seacock where that hose goes thru the hull. (and close that valve when you are not aboard).

 

[Plymouth Sailor]

It's not that simple. Freeboard is much lower for sailboats and it's not unusual for the drain on your sink to be only inches above the DWL. This should not injure your mind. Just be sure that there is a proper seacock where that hose goes thru the hull. (and close that valve when you are not aboard).

Ah I see, (I think), so a seacock must involve a ball to block the water from coming up the drain and also let’s water out (with valve open). Correct? I’ve been sailing for 40 years but never dealt with thru-hulls below the waterline.

 

[Davidasailor26]

Ah I see, (I think), so a seacock must involve a ball to block the water from coming up the drain and also let’s water out (with valve open). Correct? I’ve been sailing for 40 years but never dealt with thru-hulls below the waterline.

No, the seacock is just an on/off. It’s closed to protect the boat when the item it’s servicing is not in use or when the boat is unattended.

Galley sinks on sailboats are usually close to the centerline, so as the boat heels it stays above the heeled waterline. The bottom of the sink is probably close enough to the static waterline that it would be hard to get a drain hose out to the side of the boat with a good enough slope to drain well.

 

[jssailem]

Correct

Yes.
It is also a bit less ovbious what you are washing down the sink when it exits the boat below the waterline.

 

[jssailem]

David, from a functional perspective you are both correct.

 

[BAD ORCA]

Which explains why safety standards call for ALL below-waterline thru-hulls to remain closed except when in use. It used be that those same safety standards also called for putting all thru-hulls/seacocks in easily accessible locations. But when boating industry's target market demanded that boats had to be floating condos with decor trumping safety, floating condo buyers bega deeming thru-hulls/seacocks "ugly", builders took to hiding them...under the companionway steps, in settees (under a pile of stored stuff), behind drawers under berths, in the engine compartment...I can't even count the number of owners I've "met" over the years who didn't even know where their toilet intake thru-hull was! Needless to say, it's now common to talk to owners who've never closed any seacocks, even those who know where they are!

--Peggie

I dont know why they would want to hide them. I want to install a plexi window so i can stare at my beautiful bronze babies whenever i walk by, especially after how much i paid for them...im thinking they are more like functional art now.

 

[Ralph Johnstone]

I want to install a plexi window so i can stare at my beautiful bronze babies whenever i walk by, especially after how much i paid for them...im thinking they are more like functional art now.

If those were mine @BAD ORCA , I would spray them with protective acrylic (Krylon) to preserve the appearance, You can't take much pride in them after 24 years even in a dry location:

 

[BAD ORCA]

oh i didnt know you could do that. will definately think about that as i get the v-berth finished up. they will look good against a nice fresh white layer of gelcoat.

 

[RoyS]

My refrigerator uses a heat exchanger built into the thru-hull for the galley sink. This in place of a cooling water pump system or a fan cooled system. While I was skeptical when I installed the heat exchanger/thru-hull, I have been pleased with its performance. You, of course, have to leave the thru-hull open while the fridge is running, which in my case is only from May to October.

 

[nramsey]

That's an opinion. Then you have to worry about polymer degradation. That's another can of worms that folks don't like to talk about...

In short - there is no free linch.

dj

Do you worry about your hull degrading?
I doubt if they degrade enough faster than the polymer hull they are epoxied to.

 

[dLj]

Do you worry about your hull degrading?
I doubt if they degrade enough faster than the polymer hull they are epoxied to.

That depends upon which polymer they are made from. However, as far as I'm aware, all the good quality thru-hulls of this type have a recommended life of (I think) about 10 years. The biggest problem, from my perspective, is that there is virtually no visible degradation mechanism for these materials. So when they are about to break, there is no real obvious surface appearance. Bronze thru-hulls on the other hand typically show corrosion mechanisms. Granted, sometimes it is hidden and not so visible, but the polymers used for thru-hulls have little to no visible signs of no longer being safe.

The material your hull is made from is very different from the material these types of through hulls are made from. That is not an accurate comparison.

dj