Brian, Not sure if this will get to you. This is the first time I've used this part of the forum. Our hot water tank is working fine. I'm not sure about the plastic fittings. If you can access the inside of the tank through one of the inlets, you can check the inside of the tank in the following manner. Take a small 12volt light and solder wires to the light. Next tape it off to prevent shorting it out . Connect it to a flashlight battery. insert the light into the tank. Next look through the other inlets to see what the inside of the tank looks like. This may not let you see everything, but it should give you some idea. I took my tank to a welder and had him cut the top off of the tank for inspection. After inspection he welded the top back on. I was being a purest and wanted to keep the original tank. You may find it cheaper just to replace the hot water tank with a new unit. Hope this is of some help.
Don

Hi NorCal, saw your post where you dissected a Bowen water heater tank. I had an issue with my 66 international sovereign where the hot water flow slowed to a trickle. After taking the thing out I found the white PVC sleeve in the cold and hot ports where squeezed into the pipe. I wasn't sure what these were for so I attempted to remove the blockage. Having looked inside one of these things,can you tell me if these sleeves have any function inside the tank? The pipe threads are messed up too (very soft). I may have to do some welding to save the tank anyway. Is your repaired tank still holding up? Not only do you have a lot of time on your hands you look like you know what you're doing. How else are you going to learn how something works if you don't tear it apart?

Brian