Polyethelyne Water Tank Inspection Port and Tank Vent Changes

Fresh/Waste Water Systems, Watermakers, HVAC, Refrigeration...
Post Reply
Mark K.
Posts: 61
Joined: Sun Jul 31, 2016 4:32 pm

Polyethelyne Water Tank Inspection Port and Tank Vent Changes

Post by Mark K. »

Project 2:
One of this winter's projects has been to address the issue of the inspection port on the fresh water tank leaking water from inside the tank to the outside. Whenever I over-fill the tank or the boat heals excessively the factory installed inspection port leaks around the ring and possibly around the cap. A lot. The problem is twofold. First it is hard to get any kind of adhesive to bond to polyethylene and the second is the top of the tank can flex causing any actual sealing of the ring to the tank to only be only temporary. I am also not convinced the screw in cap with it's very thin sealing ring can actually hold water in the tank when under load. This is what I found when I removed the old inspection port. Cap, Ring and fiberglass backing ring from inside the tank that the screws bite into. The backing ring ceased being flat many years ago.
My solution, I admit, is overkill.
I installed a Sea Built stainless steel inspection port. It consists of 8 studs on inside ring and inner black gasket. I enlarged the hole in the tank and drilled the holes for the studs. I then installed the outer gasket which sits on the top of the tank and is tight around the studs holding the assembly in place.
The inspection port comes with a heavy stainless steel round cover which I used as a drilling template to make an octagonal Lexan cover and I also made a thin topping plate out of some stainless sheet metal I had with a big hole cut in the center. This clear cover allows me to check my water level and clarity without having to take the lid off. I secured it with stainless fender washers and stainless nuts.
So now the inspection port is has a double gasket (inside and the outside) and the top of the tank is sandwiched between the gaskets. I am sure this will be the end of my leaking problem. I can still remove the nuts and the clear Lexan cove to clean the tank when needed.
Overkill? Yes. Problem solved? Oh yeah!
The other problem I am hoping to reduce is the stagnate water smell in the boat. I noticed when the water leaked past the old inspection port the water would puddle under the tank and is nearly impossible to remove or dry out.

Project 1:
Sorry No photographs. Several years ago I noticed slime growing in my fresh water tank that required cleaning the tank several times a season. It appeared to be the same nasty stuff as I sometimes found in the bilge. The culprit was the factory vent system The water tank was vented up into a cabinet on the port side where a vented loop was installed and then down into the bilge. The idea is that if water ejects from the vent line it would go harmlessly into the bilge. However this also meant that as fresh water was used up it had to draw air from the stinky bilge and with it whatever bilge microbes went with it thereby contaminating the fresh water tank repeatedly. The vented loop also kept the inside of the cabinet too moist and I had a constant mildew growth in there. So I removed the vented loop and connected the vent line to an unused spout in the galley sink as I had once seen done in a friends West Sail 32. Now much fresher cabin air is drawn into the tank and the slime problem in the fresh water tank has been solved. Also the cabinet is not longer damp, mildew free and now finally usable space. Lastly when I fill the tank and the spout shoots water harmlessly into the sink I know the tank is full.
Attachments
Clear Lexan Cover with topping plate and nuts
Clear Lexan Cover with topping plate and nuts
IMG_2457.JPG (317.12 KiB) Viewed 2341 times
Enlarged hole with top Gasket showing
Enlarged hole with top Gasket showing
IMG_2456.JPG (213.64 KiB) Viewed 2341 times
Cap, Ring and fiberglass Backing Ring.
Cap, Ring and fiberglass Backing Ring.
IMG_2405.JPG (510.88 KiB) Viewed 2341 times

User avatar
newt2u
Posts: 236
Joined: Wed Sep 11, 2019 11:24 am
Location: UK

Re: Polyethelyne Water Tank Inspection Port and Tank Vent Changes

Post by newt2u »

I like overkill nice job.Not sure what access you have to your bilge problem but, if you no longer have a leak problem, perhaps you can get a tube into the bilge and pump out the water and finish off with a desiccant.
Rockin - F21 twin drop keels - located Whitehaven, Cumbria, UK

Bluemeenie01
Posts: 15
Joined: Tue Dec 19, 2023 4:51 am

Re: Polyethelyne Water Tank Inspection Port and Tank Vent Changes

Post by Bluemeenie01 »

Can you post a picture of what the Spout looks like to the sink?

Did you just run the line underneath along with the main water line to the galley sink and installed a spout that the line ran into?

Also, I'm about to buy and mount the Seabuilt Tank access plates and am trying to figure out if I should go with the 10" or the 14" stainless steel so as to give me more room to clean out the 2 fresh water tanks.

What size did you use?

Michael

Mark K.
Posts: 61
Joined: Sun Jul 31, 2016 4:32 pm

Re: Polyethelyne Water Tank Inspection Port and Tank Vent Changes

Post by Mark K. »

I used the Seabuilt 8" inspection port which provides a 6" diameter hole. I think you only need a hole big enough to get your forearm through. I don't have a photo of the sink spout handy. I'm not sure if it came from the factory or was added by a previous owner. It was a dedicated spout for filtered drinking water from the fresh water tank. I just use jugs of spring water for drinking so I had no use for the filtered water spout.

Post Reply