Installing a through hull with no inside access

[mncruiser]

I’m going to be installing a larger vent for my holding tank. I only have reachable access to the outside of the fitting. Since this is far above the waterline, any tricks or types of fittings I can install with only access to the outside?

Ideally I’ll be installing a 1” hose mushroom fitting. It probably needs to be a 90 or a 45 degree angle, but if I can do straight I’d prefer that.

Any ideas? Thanks

 

[backinblue]

Why is that necessary, just curious.

 

[dhays]

I’m going to be installing a larger vent for my holding tank. I only have reachable access to the outside of the fitting. Since this is far above the waterline, any tricks or types of fittings I can install with only access to the outside?

Ideally I’ll be installing a 1” hose mushroom fitting. It probably needs to be a 90 or a 45 degree angle, but if I can do straight I’d prefer that.

Any ideas? Thanks

If you can't access the inboard side of the fitting, how are you going to attach the vent hose?

 

[Comodave]

Can you install an access plate to get to where you need to be? Without inside access how do you plan on tightening the nut on the through hull? And putting the hose on the through hull.

 

[psneeld]

I have used these in similar situations.


You install the hose on the barb, snake the fitting up and thru the pre drilled hole, screw on the exterior nut with sealant on it, let it set, then trim off the extra thread. looks like most any other thru hull.

 

[Comodave]

Neat, I hadn’t ever seen those.

 

[Frosty]

I like the idea of somehow gaining access to the inside (choosing a different location, maybe a "deck plate" on an interior bulkhead or furniture part to give you access). As shown above there are ways to do it without access but that somehow feels like it would come back to bite one later.

(There are enough of those sorts of installations on boats already!)

 

[Dougcole]

I think a deck plate is your friend in this situation.

 

[mncruiser]

Why is that necessary, just curious.

The pursuit of an odor free holding tank with no filters and minimal chemicals. If you see references to Peggie Hall’s book “Get Rid of Boat Odors” here it’s a key part of an odor free system.

Worth the purchase on Amazon. Peggie is also a frequent poster here as “Headmistress”.

 

[Comodave]

Having more than one vent and larger vents will definitely help with the holding tank smell. Another way to do it without adding or enlarging the vent is with a system like the Groco Sweetank. It works, we had a horrible smelling holding tank in a previous boat. Bought the Sweettank system, took about an hour to install and then in 2 hours of run time the smell was absolutely gone. We never added any chemicals to the holding tank for the rest of the time we owned the boat. Only hard part of the install was getting my finger to pull the trigger on the drill to drill the 2” hole in the top of the holding tank.

 

[Bacchus]

Have you looked for other options that might provide interior access?
I had a simi,similar, dilemma with our Mainship even with an access plate no way to replace the factory thru hull with a mushroo. Type full open flow thru vs typical fuel vent fitting. I finally gave up and found a way to route forward to the bow and put a thru hull just be,or the anchor locker with access fro. Fwd cabin headboard. Venr run under bed to holding tank pretty simple even with no large access.
Also installed a cheap DIY holding tank bubbler that worked wonders. More info available on bubbler if interested.

 

[mncruiser]

Have you looked for other options that might provide interior access?
I had a simi,similar, dilemma with our Mainship even with an access plate no way to replace the factory thru hull with a mushroo. Type full open flow thru vs typical fuel vent fitting. I finally gave up and found a way to route forward to the bow and put a thru hull just be,or the anchor locker with access fro. Fwd cabin headboard. Venr run under bed to holding tank pretty simple even with no large access.
Also installed a cheap DIY holding tank bubbler that worked wonders. More info available on bubbler if interested.

I’ve got to look closer. It’s a Mainship 390, so may have a similar problem.

 

[mncruiser]

Have you looked for other options that might provide interior access?
I had a simi,similar, dilemma with our Mainship even with an access plate no way to replace the factory thru hull with a mushroo. Type full open flow thru vs typical fuel vent fitting. I finally gave up and found a way to route forward to the bow and put a thru hull just be,or the anchor locker with access fro. Fwd cabin headboard. Venr run under bed to holding tank pretty simple even with no large access.
Also installed a cheap DIY holding tank bubbler that worked wonders. More info available on bubbler if interested.

That’s a darn good idea. I bet you get good airflow there too!

 

[mncruiser]

I have used these in similar situations.


You install the hose on the barb, snake the fitting up and thru the pre drilled hole, screw on the exterior nut with sealant on it, let it set, then trim off the extra thread. looks like most any other thru hull.

Kind of what I was thinking with the fitting, using something like this

 

[dhays]

Also installed a cheap DIY holding tank bubbler that worked wonders. More info available on bubbler if interested.

I would second this suggestion. Following Bacchus’ example, i did the same thing. A DIY install was cheap and pretty easy. It completely eliminated any odor from the holding tank. Low amp draw and pretty bullet proof. Eventually the fish tank aerator that I used will fail, but it was really cheap to buy and it would be super easy to swap out a new one. Mine has been installed for 3 years now.

 

[mncruiser]

I would second this suggestion. Following Bacchus’ example, i did the same thing. A DIY install was cheap and pretty easy. It completely eliminated any odor from the holding tank. Low amp draw and pretty bullet proof. Eventually the fish tank aerator that I used will fail, but it was really cheap to buy and it would be super easy to swap out a new one. Mine has been installed for 3 years now.

Would love to hear more about the bubblers and how you installed. Thanks!

 

[dhays]

Would love to hear more about the bubblers and how you installed. Thanks!

https://www.trawlerforum.com/forums/showpost.php?p=1017315&postcount=1

 

[Bacchus]

Would love to hear more about the bubblers and how you installed. Thanks!

Sean
More info available on my Bacchus website Projects Pg 2. https://dkloeber.wixsite.com/bacchus/projects-pg-2
I installed this in spring of 2015 and original pump still runs 24/7 during every NE boating season.
Only mods I have made are
1) moving the location from fwd of a bulkhead to aft in engine rm to minimize noise at night
2) changed out the tube in the tank to pvc as the metal did corrode. I used a long faucet connection tube and plugged end and drilled a few holes.
I fully expected I'd have to replace the air pump before now but these things seem to just keep running.
Where you enter tank not important... I used an existing outlet but have seen others add new from top with dip tube and a simple T at bottom.