August 2022

 August 6,

There was really nothing to do but to cut out that connecting channel and start over.  I removed the tanks, cleaned up the old welds and made a new connecting channel.  I had just enough room to weld the connecting channel to one side with the tank removed and slide it into place when done.  This allowed me weld both sides and ensure a water tight joint.  I'll still have to weld the other (port) side when the tanks are in place. 

The new connector tube with plumbing attached.

Refitting the tanks.

All back together.

Well, I still have a very small leak along two seams.  It took me a few times grinding the seams down and re-welding to reduce that to a small weep.  Not much more than a sweat bead.  The amount of work done thus far is ridiculous. I think this is my first not so happy outcome.  My intention is to seal all the welds with epoxy.  I'll have to clean the tanks with alcohol and rough up along the seams with some sand paper.  I've already tested the bond strength of epoxy on the HDPE with the proper prep and there is a nice bond. Specifically, I'm going to mix up a quart plus of epoxy and pour in the lowest part of the tank that has the connector tube.  Basically, I'm flooding the area that is susceptible to leaking.  If I can get about 2-3 mm of epoxy floating on the low side of the tank, it will warm up and seep into any voids and small cracks permanently sealing the tank.  I hate to cheat like this but I just can't get the tank fully sealed otherwise.  If the weld is not perfect, you get a cold joint.  The conditions really have to be perfect and that is very difficult welding the connector when the tanks are already installed in the bilge. Luckily, the water tanks will be fully welded and tested outside of the boat where I can make better repairs if there is a leak. Specifically, I'll have full access to all welds on the inside and outside of the tanks.  

Aug 19,

The holding tanks are sealed and almost ready to have the tops put on. I've decided to go ahead and lay all the plumbing runs before I locate where the two main 1.5" lines from the head will attach.  These two lines will carry waste from the heads and the three wash basins in the cabins. The Kitchen sink will also drain into the port waste line.  All of that water is gravity fed into the tanks.  The two shower drains go to a closed sump and are pumped into the tank.   I'm also working on the freshwater runs so I can locate where the water will drain from those tanks.  

The brown lines represent the waste water system and tanks.  The blue and red lines are the fresh water system.  Blue for cold and red for hot water.  It's a rough design but enough to get started. 

The fresh water tanks can be tested for leaks on a bench top instead of in the bilge.  Much easier.  I did have some issues in the corners where all the HDPE faces come together.  So there was some grinding and rewelding at those places.  I'm going to go ahead and do the same for the other tank before I test because there is an obvious weak point at those corners.

The drain for the fresh water tanks is attached via a 1/4" thick EPDM gasket and set in a small well to allow the tanks to fully drain.  A 1/2" PVC elbow is screwed into the tank bulkhead fitting and a ball valve is glued to the elbow.  Each tank will have its own valve so they can be individually shut off.  Half inch PVC pipe will run to the edge of the tank supported by a bracket (not shown) and then we convert to 1/2" PEX.  The PEX will run to a tee which connects both tanks and then runs aft via 3/4" PEX to the pressure pump.  3/4" PEX is run all the way to the water heater (under the sink) and forward to where it splits and reduces to 1/2" to go forward and to starboard to the separate wash rooms.  At the water heater (tankless powered by propane), the cold and hot water tees to the kitchen sink.  The kitchen sink drains directly into the black water tanks at a junction that receives the waste from the port head and the port cabin wash basin and the vee berth wash basin.  The starboard was basin and head drain into the starboard black water tank (holding tank).  All of the above waste lines are gravity fed.  The two showers drain into a well pump and are pumped up into the black water tank using a tee at the tank connector where the pump-out is connected.