Fresh water system

First test

In June 2022 I filled the small tank, plugged the toilet hoses, and checked the fresh water and the sump. All worked well. A bit too much water was left over in the sump, and it needs a cover.

In September the gray water port was re-bedded with 3M 4200.

The day tank disaster

Earlier I had filled the tank, and a week later all the water was in the bilge. The tank is built into the boat, so I suspected a hose. To find out, I had to close the gate valve on the tank outlet. It was stuck, so I took it out, freed it and cleaned it. Not too hard.

I closed it, filled the tank... and saw a nice stream running out of the bottom of the tank. So I had to open it up.

And then several things pushed me to spend real money on it. The lid was just painted plywood, and it had rotted, of course. The inside of the tank had lots of pinholes with brown stuff in them. Nobody knows what paint is in there, and it's definitely not for drinking water. And there was a crack along the very bottom corner. Conclusion: rebuild the tank with materials made for drinking water.

I went shopping for an FDA-approved potable water tank coating. Most of them come only in barrels. I found a few in realistic sizes:

• Jotun Tankguard DW, in 40-gallon containers.
• LiquaTile 1172, $278 for 3 quarts.
• Belzona 5812 DW, $575 for 3.5 liters (one 10 mil coat, up to 140 sq ft).
• Belzona 5892, $850 for 4 liters, for hot environments.

TotalBoat suggested their polyester finishing resin, but it's not certified for drinking water. After long thinking I picked LiquaTile 1172.

I sanded the whole tank to get rid of the flaking paint and open up the crack, and found a pretty big void in the bottom, just left of center, with a crack across the whole bottom. To fix the leak I glassed the whole bottom: thickened resin first, then two layers of 1708 on the bottom corner, wet on wet, each a little offset so there's no step. That's me and the tank.

My glassing table is covered with butcher paper, so the resin doesn't ruin it and the wet glass doesn't stick.

Then came two coats of the liner. I put paper and the original lid over it to keep the dust out.

In November, with the tank finished and filled, the water had no smell and no taste. I didn't know what paint was on the old plywood lid, and plywood plus water means problems whatever paint you use. So I made a new lid from food-grade HDPE, with an electric level sensor. Then I tried the water system, found the old galley faucet leaking, replaced its O-rings, and finally had water to wash my hands and face at the end of a hard day. A small luxury that felt huge.

The front tank, and the mysterious hole

Through the inspection port of the front tank I could see osmosis pox and brown traces. Not good for drinking water. The lid screws were black drywall screws, rusted like hell, most of them driven in at 45°. When I tried to undo them, they snapped at their rusty necks. So I cut the lid into pieces to get it off. It looks like somebody had used Liquid Nails instead of sealant.

And the most mysterious thing: a 6 mm hole drilled in the middle of the tank bottom. I didn't believe my eyes. I thought it was chipped gelcoat, so I pushed a screw into it, and it went right in.

There was osmosis pox all over the inside. I'm not worried about strength, but about chemicals getting into the water, and whether the surface could hold a two-part coating. Around the frame it looked like three different attempts to mount the lid, with no thought that every hole in the frame is a future leak. A lid of exterior plywood, of course. And the cherry on top: the drilled hole. Who? Why? What for? More questions than ideas.

I sanded and filled all the pox, the frame holes and the bottom hole, glassed over them, and added tape on the bottom edges. Then two coats of LiquaTile 1172 inside. It's the only product certified for drinking water that I could buy in a sane amount, and three quarts was exactly enough for two coats. It's made for concrete and steel, but the maker confirmed it works on fiberglass. It's really hard to work with: very thick, and no thinners allowed. It cures to a nice gloss, except where I put it on too thick and it ran. Not a cosmetic surface, so who cares.

The only compromise was butyl tape on the lid. My plan: fill the tank completely with city water, freeze a sample while filling, wait 2–3 weeks, take a sample from the tank, and send both to a lab. I never had the chance to do it.

Testing tanks and the holding tank

In December 2022 I filled both tanks to the top, even overfilled them up into the lids, to test the seals. The big tank's lid was sealed with butyl and its fittings with 4200, the small one with silicone. We'll see which lasts longer. You can see a few shades of white inside the new tank: some spots of coating got damaged, but only cosmetically. I sketched humps to protect the electric level sensors and make the lid nicer to sit on.

Both tanks were full, and the gravity transfer from the big tank to the small one works.

Then the opening I had cut under the holding tank, looking for the lightning ground. Remember, I found nothing there but empty space, and no way to get under the compression post. I put a support plate in, screwed from the back with countersunk screws, set the original piece back on epoxy and laminated two layers of 6 oz cloth over it. No strength needed, just to seal that space.

Then a new sanitary hose to the pump-out port. The holding tank went back in its place, held to the floor and the bulkhead with wood blocks and copper straps, with an electric level sensor.

PEX, and four days of zip-ties

"Don't try to make it better if it works!" Short story: my boat is 40 years old, and all the hoses were original, hard and starting to crack. I didn't want to wait for them to burst, so I replaced the old PVC hose with PEX-A.

Why PEX-A? The crimping is simple. You can expand the pipe somewhere comfortable and then install it in a hard place. The fittings are cheaper than SharkBite, there are no metal rings as in PEX-B, so no corrosion, and the expander tool isn't expensive.

Easy to say. In my head it was simple: take off the clamps, tape the new PEX to the old hose, and pull it through, using the old hose as a guide. A couple of hours, right?

In reality: four days. Why? All the hoses were tied with screw-mount zip-ties between the hull and the liner, in places you can't reach. I couldn't pull them, so I looked with a borescope and saw the zip-ties. Why did Irwin do that? Probably all the plumbing was done on the liner before it went into the hull, and the zip-ties held the hoses in place during assembly. Nobody thought anyone would ever replace the water hoses.

• Trap 1: the hose from the front tank to the port tank, tied 5 inches under the toilet. From the front cabin locker my hand was too short and too big. I had to cut a 2x2-inch hole in the floor next to the toilet. Crazy, I know, but I don't think 40-year-old heater hose is good for drinking water.
• Trap 2: behind the starboard settee, from the head to the galley, tied in three places with no access. There's a "bulkhead" in the middle of the settee that the hoses go through, but on my boat there's about an inch of gap between it and the hull. So I cut the old hoses, pushed them out of the original holes under the nav desk, then pushed and fished the PEX through to the head.
• Trap 3: from the galley to the water heater in the engine room. The hoses are foamed in under the ice chest, in some high-density stuff. The best way was a new path between the ice chest and the engine room: enlarge the exit hole, lay the new pipes over the old hoses and leave the old ones there. Luckily, on my boat it was mostly soft foam I could dig through with a stick, and only 3–4 inches of hard foam near the aft corner had to be drilled.

But I did it. Plus maybe a day to close the hole by the toilet and replace the foam. A lot of work, but it pays back in confidence in the water system.

In the galley I added a 0.75-liter accumulator, and ball valves instead of the garden hose splitter that used to switch between the foot pump and the electric pump.

In the head cabinet: a separate line for the shower head, with electric valves and ball valves. The electric valves will work from a foot switch, so water only runs when you need it. And the hot water "primer": an electric valve from the hot pipe back to the tank, to drain the cooled water from the hot pipe before you start, so the faucet gets hot right away.

Pump and water heater

In June 2025 it was clear: if I want a working shower and a fresh water toilet, it's time to upgrade the 40-year-old pressure pump. The new one is a variable-speed pump: 70 psi and 5 GPM. Yes, it's a bit dirty down there. It's a 47-year-old boat, and some places just aren't shiny.

In July came the water heater dry fit in the engine room. I bought a 6-gallon, 120 V Kuuma 11811. It's 13.625 inches high, 13.75 wide and 19.75 deep; some websites say 19 inches high, which is wrong. It fits in the engine room tight but nice, as if it had been made for the Irwin 34. Mine has mounting plates front and back, so I made an aluminum bracket that the back plate slides under, then screwed the front plate to the floor.

After the heater went in, there was almost no floor left to stand on in the engine room. So I made a removable floor panel, mostly over the drive shaft, which also protects the depth finder and the speed sensor. Here's the templating.

A week later it was finished. Nice and clean. I'll put a plywood board on top so I can step on it more or less safely. The connection hoses aren't "marine grade", but they have a synthetic braid instead of stainless, so they'll probably last a bit longer. The hot water priming for the shower is tested. It works great!

I also moved the coolant expansion tank to starboard, where I can reach it better.

The butyl lid leaks

In August 2025, about two years after rebuilding the tanks, I finally started using them, and right away found the front tank lid leaking into the V-berth.

The funny thing is that it came down to the sealant. The small port tank had silicone, and on the big front tank I'd tried butyl. Butyl itself wasn't the problem. In one corner the gap between the tank lip and the lid was too wide, so the tape never got squeezed. That left an open path, and of course, a leak.

To find it, I hooked the shop vac up in blow mode to pressurize the tank and sprayed soapy water on the seams. The bubbles showed it right away.

"Just reseal it" sounds simple, but first the lid has to come off. That was a real fight. It was cut so snug that there was no room to get anything under it, and butyl doesn't let go easily. After scratching at the seam a few times, I came up with a trick. I took out all the screws and let the shop vac blow into the tank. It only makes maybe 3–5 psi, but the lid is about 20 by 30 inches, around 600 square inches. Even at the low end that's a couple hundred pounds pushing up. Sure enough, it popped the lid up a little. Then I could get screwdrivers into the gap and work around until it came free.

Cleaning off the butyl was another problem. It really only comes off mechanically, with a knife blade. And butyl sticks to HDPE like crazy. Cleaning the lid took an hour by itself, and another hour for the tank lip. But I found a trick: spray soapy water while you scrape. Without it, the little bits of butyl kept sticking back to the surface I'd just cleaned. With a spray bottle of Dawn, hand soap and water, it stopped sticking and went twice as fast and much cleaner. A final wipe with acetone, which doesn't dissolve butyl but softens it a bit.

After about two hours of cleaning, I ran a nice thick bead of silicone and carefully dropped the lid back on. I tightened the screws only until the sealant squeezed into the seam, so the silicone works like a gasket. A week later, when it had cured a bit, I tightened them down to really compress it.

Bleach, a fill controller and a real inlet

March 2026, in Kemah. The water heater went back in with a new riveted aluminum bracket on its front ear. With the original mount I had to remove the electrical box every time to get to the screws. The new bracket is shaped so the screws take only side load, not pulling. And the heater got an IP68 power connector. I also pulled the empty black water tank and checked the inlet flange: 1.5 inches.

In June 2026 I noticed a fishy smell from the fresh water tanks, so it was time for a proper sanitizing. I chlorinated the whole system: 300 ml of bleach in about 80 gallons of water, flushed through all the lines and left for about 20 hours. Then I drained and refilled the tanks with city water three times.

Filling the tanks is never fun. I had designed a water fill controller a while ago but was too lazy to install it. Now it's in. At power-up it opens a solenoid valve in the fill line, an inductive sensor sees when the tank is full, and it shuts the water off. While filling, it beeps briefly every few seconds, so you don't forget the water is running. When the tank is full, it switches to a much more annoying half-second beep every second, to remind you to disconnect the dock hose. Very effective. Nobody can ignore it.

Why electronics instead of a simple float valve? First, I can design and build electronics myself, make them reliable and keep the cost down. Second, a float valve inside the tank means opening the tank when it fails, plus some fiddling so it fills completely without overflowing. An outside float valve needs extra plumbing to sense the level, and on a sailboat there's always a chance of water finding its way into the bilge when you heel. With the electronics, everything I'd service stays reachable (at least for me), the tank fills almost to the top, and I get an automatic shutoff plus a reminder. I also added a fuse panel in the HVAC compartment.

Two weeks later I installed a proper shore water inlet, with permanent plumbing to the tank. No more feeding the hose through the hatch and crawling under the V-berth every time. Much quicker, cleaner, and way more convenient.