It sounds so medical. It's not. It's technical.

Here's some parts.

This immensely complex T-fitting with appropriate hose barbs all around.

It's wonderfully Byzantine.

The deck filler has a bushing to narrow it from the default 1½″ to 1″. This is actually good because the tiny opening from anchor locker to the top of the tank is only big enough for 1″ hose.

The bladders only accept 1½″ fill fittings. So. The T in this picture splits the 1″ from the deck to two 1½″ for the two bladders.

Weird, I know.

Here's the lower bladder in place. The band of white is part of the shelf that will hold the upper bladder.

I capped one side of the T fitting. Built the "drawing" lines to take water from the bladders to the fresh-water system.

And.

It worked.

Deck water in. It sat in the bladder. And it came out into the galley sink. A few things dripped, but a quick twist with the tool and the hose clamp was a little tighter and drier.

Not surprising. Really.

CA and I are both software people. We find it necessary to test everything in isolation before moving on and testing the entire system.

Also. CA lives by the "change one thing" rule. When something doesn't work, change one thing. If you fixed it, you also know the root cause. If you change too many things at once, you can't correctly diagnose which change fixed the problem.

The upper bladder (when full) can hold 135 liters; about 135 Kg. It cannot be moved when full. Even half-full, 67½ Kg is not something you can lean over and mess around with.

So we tested the lower bladder to be sure we don't need to look around in there again. Looking at the lower bladder isn't easy and requires planning. If you're going to dump the upper bladder's water, you're going to want to refill it after. A borescope camera with a long gooseneck would be required to see under the top bladder without wasting fresh water.

Putting fittings into the Nauta bladders is a challenge. The hole seems just a hair too small; but that's how you prevent leaks. The Nauta Flexible Tank Fitting Install video (https://www.youtube.com/watch?v=xh-u5FVMTXU) is essential. We had bicycle tools, which are better than using the plier handles shown in the video.

Tomorrow is upper bladder install. Then the wash-and-sanitize cycle described on the page of instructions that comes with each bladder. See https://www.defender.com/pdf/NAUTA_FLEXIBLE_TANKS.PDF for the Maintenance Instructions.

I'm not happy with the 1½" hose I ordered. It's too thick: I can't get the hose clamps tight enough. I think it's designed another kind of higher-pressure fitting. I need to get what McMaster-Carr calls "Soft Plastic Tubing for Air and Water". Eventually. What's in there now mostly works. The drip is slow, but it doesn't seem like I can eliminate it without buying more hose.

We're excited to be cleaning and filling the tanks. This lets us move on to cleaning the starboard tank under the saloon (which doesn't leak.)

And then.

Putting four rigid plastic tanks in the space formerly occupied by the port tank. The port tank started leaking last year, and the bilge pump cycles were the impetus to start upgrading our water system. I think I can put 4 tanks, each 34″ × 17.5″ × 11″ into the space formerly occupied by the port tank. This may be optimistic. We have a pile of cardboard just waiting to make models.

Step one, however, is to get the old lid off the tank. This will be some awkward reciprocating saw work to cut all the rivets and then get the aluminum up from under the floor. It has to come out in sections, so there will be a lot of cutting. It will be loud and painful.