Thru-hull replacement

[sune]

Hi,
This thru-hull is not in use. Was for water inlet for head (I'm pretty sure).
It needs replacement, right?
I have no intention of installing a head this coming season, but maybe in the future so I don't want to glass the hole. Besides I never worked with fiberglass and maybe my first try shouldn't be below waterline.

What's a good and safe solution?



Thank You

[sailormed]

Judging by the diameter of the hose on the photo it looks like a 38mm hose and that is for a head outlet to sea pipe.
Otherwise the seacock doesn't look to bad on the picture.
Can you operate the wheel open-close without a lot of effort?

[JPA Cate]

Hi, sune, welcome aboard CF.

Yes. You need to have a proper seacock there, not that corroded gate valve, which are unsafe... We use ball valves that are screwed into the through hull fittings. Buy tapered timber plugs, for each through hull you have, and keep it next to each one, so if they ever fail, you can plug the hole. The water comes in in a great spurt, rather startling if you don't expect it. https://search.defender.com/?express...valves&x=2&y=4 The link has a picture of one.


Ann

[sune]

I cant operate it by hand, haven't tried with tools.

Here's a picture of the other one. Then I suppose this is the inlet?

[pmagistro]

That thru hull fitting looks pretty scary to me. Gate valves are inappropriate on boats, let alone below the waterline, even when new. That one almost certainly won't function. I would encourage you to remove it and close off the hole (reference https://adventuresontheclub.com/2015...th-fiberglass/) or replace it with a proper bronze thru hull and seacock with a nice backing plate. http://www.pbase.com/mainecruising/seacock_primer is a great reference for how to do it right.

[sune]

hmmm. I'm considering removing the thru hulls and closing the holes.
But then, that'd be silly if I decide to install a head next year or later.

Considering the Trudesign products (but that might be a whole different topic).

Is there a safe way to plug a thru hull without installing a seacock valve until possibly installing a head later. Just to save the money for now. Or is that considered bad practice?

Thanks very much for the replies!

[pmagistro]

Agreed. I replaced 11 thru hulls in my boat. The peace of kind that comes with solid, well-made, functional seacocks is worth the time and money, in my opinion.

[MerryBee]

sune:
...please listen to the good advice given here! It's allot of work glassing over the hole, and you'll be really PO'd if you decide you want that thru-hull later on down the road.
As for installing a head, what model boat is this; do you daysail, occasional overnights???
Since we are primarily coastal cruisers with easy access to pumpout facilities, we went with the Thetford model 550 porta-potti with deck pumpout option. It handles 3-4 people for up to 3 days and is completely self-contained. No hoses, no tanks, no thru-hulls, no problems!

[sune]

MerryBee:
The boat is an old 24 foot sailboat from 1971. it's a Bandholm 24. Built here in Denmark. Solid fiberglass.
I'm a newbie, just got my sailing license recently and bought this little old boat. I think I'm gonna do daysails and occasional overnight as you guess. No long trips any time soon :-)
Thanks for recommending the Thetford 550, I'll keep that in mind.

[mike d.]

You should be able to buy bronze caps for the through hulls, at a chandler ! as the boat is not in the water unscrew the valves, and take to the chandler to match the thread ! When you install, put pipe dope on the threads so they will be easy to take off if you go back to a regular head !

[meirriba]

Originally Posted by mike d.

You should be able to buy bronze caps for the through hulls, at a chandler ! as the boat is not in the water unscrew the valves, and take to the chandler to match the thread ! When you install, put pipe dope on the threads so they will be easy to take off if you go back to a regular head !

As the boat is out, this would be the easiest procedure. Glassing the hole is complicated and you need to know how to work with GRP.
BUT - once you take out the valve, examine the through hull itself for corrosion/integrity as well.
If it is sound, proceed as above. If it needs replacement, do it - it will be still safer/easier than closing the hole (IMHO that is...).

[ErikFinn]

Hi Sune,
here is some of the best read you can find on the subject:

https://marinehowto.com/replacing-th...-and-seacocks/

https://marinehowto.com/seacock-backing-plates/

https://marinehowto.com/seacock-failure-testing/

Additionally, the photos seem to show only single perforated hose clamps, those should be replaced with good quality non-perforated ones and two pieces installed at each hose connection:

https://marinehowto.com/proper-insta...e-hose-clamps/

[sune]

Thanks for all the good advice.

I have removed the old valve and this is what the thru hull looks like.

from outside:


I have to examine it closer but at first glans it looks pretty good to me.
I would love if I don't need to change it as I prefer to not mess around with holes under the waterline if I can avoid it. But if I must then that's ok.
Most important is peace of mind.

How about closing it with something like a combination of these plus pipe dope:


Is that a reasonable or a horrible idea?

Regarding backing plates, Marine Howto writes:
"Unless your hull is close to an 3/4″ thick, of solid fiberglass, you’re going to need backing plates for the seacocks."
I the old hull is definitely solid fiberglas and I suspect it's 3/4" thick, but how do I go about measuring..hmm ..measuring thru hull and subtracting fittings I suppose.

[HopCar]

Your thru-hull fittings appear to be made of DZR Brass. This is a commonly used metal for thru-hulls in Europe. It can have up to about 35% zinc in it. Tin or arsenic is added to reduce dezincifacation corrosion. It is not 100% effective and the metal will deteriorate in salt water over time.

I would replace them with 85-5-5-5 bronze that is commonly used on US brand marine fittings. 85-5-5-5 is only 5% zinc and should last the life of the boat.

If American brand hardware is available to you, any of these brands are good: Groco, Perko, Apollo, or Buck Algonquin.

Both of the valves shown in your photos look like crap for marine use but if your just closing off the thru-hulls that’s not an issue as they will be removed.

Don’t be afraid of changing the thru-hull fittings. It’s a pretty easy job.

As for capping it, why not just use a cap instead of a coupling and plug?
This isn’t ideal as the thru-hull fitting has straight threads and the cap or coupling has tapered threads. You had that problem with your valves as well but you can probably get away with it.

If you want to keep the thru-hulls for future use, I’d replace the thru-hull fittings with good 85-5-5-5 bronze, install Groco backing blocks and flanged adapters, then cap it with an 85-5-5-5 pipe cap.

If you do that, you’re ready to just remove the cap and screw on a marine ball valve to start using it again.

[sune]

HopCar. Thanks.
Do you know of Italian brand Guidi? They make what looks like top-quality bronze fittings and they are available from local chandlers here in Denmark.

like these: https://catalogue.guidisrl.it/en/52-non-stick-valves

I think that I decided to get rid of those two thru-hulls that aren't being used, and glass over the holes. If I was to keep them for possible later use, I would want to replace them right away with better quality but that seems bit of a waste of money.

I am however definitely replacing the two thru-hulls and valves that are being used.
One for engine water intake:
engine intake 2018-01-10 13.37.56.jpg Views: 180 Size: 405.0 KB ID: 161948" style="margin: 2px" />

The other for sink drainage.

I will do it proper with quality bronze fittings, flanges and quality hose clamps.

I still don't know if it's necessary to have backing plates as the hull is solid fiberglass and pretty thick.
What do you think?