retro-fit water tank inspection hatch?

[Breezin]

Has anyone installed any kind of inspection hatch on an aluminum tank?

We recently purchased a Nordic Tug 37, which has a built-in aluminum water tank. Unlike the rest of the boat, which is immaculate, the water tank has been sorely neglected. (Wish we'd noticed this on the survey.) The pump strainer keeps clogging with what can best be described as black and grey snot. I suspect I could fill and drain it forever and not get all this stuff out. What I need is access to the inside - ideally, from the side as there's not much overhead clearance.

 

[Lepke]

You can cut a hole and later weld or bolt a patch. But there may be baffles that interfere with hand cleaning.
You have to kill the organisms in the tank. Until you do that, they just keep reproducing. You can use bleach with an aluminum tank, but strong solutions left for longer periods will stain the aluminum and even pit it. For a system that's been sitting, it's a good idea to flush all the lines and faucets with a mild bleach solution.
If you're on city water keep it fresh or drain the tank and lines.
I have filters after my tanks, you may want to do that.

 

[geoleo]

Has anyone installed any kind of inspection hatch on an aluminum tank?

We recently purchased a Nordic Tug 37, which has a built-in aluminum water tank. Unlike the rest of the boat, which is immaculate, the water tank has been sorely neglected. (Wish we'd noticed this on the survey.) The pump strainer keeps clogging with what can best be described as black and grey snot. I suspect I could fill and drain it forever and not get all this stuff out. What I need is access to the inside - ideally, from the side as there's not much overhead clearance.

Any Aluminum water tank on any boat is a disaster. Aluninum reacts with chloride which is in most Municipal water systems. The crap you see coming out is aluminum chloride which is the choline eating the aluminum.

 

[Sea Level]

These are available in different sizes and relatively easy to install.

https://www.fisheriessupply.com/seabuilt-tank-access-plate-system

 

[Pcpete]

I have a similar issue but mine is more like pebbles. My plan is to use a jig saw to cut an access hole in each of the three sections (two baffles) then clean the tank as best I can. The final prep will be a vinegar wash down. I’ve ordered a food grade epoxy called Brewcoat that’s used for coating the interior of all sorts of food holding tanks. The manufacturer says two coats at a minimum and I can close it up before the second coat is dry. For a hatch, I’m going to get some .125 5000 series aluminum and bond the cutout waste to the underside as a doubler, then that gets coated with the Brewcoat as well as the hatch flange area. I could use the Brewcoat to seal the hatches to the tank, but was advised that I’d have a real problem if I ever wanted to open the hatches. So, my plan is to use 4200 and lots of sheet metal screws.
My plan is to start after the first weekend in May. It’s the Opening Day of Boating in Seattle and I plan to be there to see and be seen as well as watching the crew races.