Does anyone know who made the holding tanks, what material they are made from, what to use to seal the 1-ĹĒ threaded Sierra plastic hose tail fittings and what the tank boss threads are i.e. BSP, NPT etc. (I suspect NPT as the tank is likely to be American made) ???
I keep getting holding tank smells in the boat. Itís been difficult to find out where the smell is coming from. Usually when we flush the manual Jabsco toilet this happens but there is always a residue smell and when at sea it can get worse. I suspected the vent but Iíve not been sure, no inline vent filter is fitted. Iíve checked the vent line, the hoses, macerator, and took a good look at the holding tank while in situ. All seems ok but Iím not 100% sure. The last straw was when we had the boat out in rough seas recently and the smell in the helm / aft seating area was just horrid. So, I decided I need to take the holding tank out and check for cracks etc. Not a nice job with some residue leakage but I got the tank out in an hour or so. Once flushed, bleached and flushed several times I plugged the holes and put a small compressed air pressure test onto the tank. Using a proprietary leak detector fluid I found no leaks so Iím kind of at a loss. The tank, now dry, really smells, the smell is from the inside. Although itís pretty clean internally there is residue white stuff some flaky looking and some fatty looking in places attached to the inner upper side walls.
Iíve been reading about the possible need to change the hoses due to leaching the foul water, they are 19 years old but look ok!. Incidentally the pump out and vacuum out hoses enters the tank at the bottom, so they are constantly flooded in foul water at their low point, this is the design. A dip tube would have been a better idea but we have what we have. Iím going to do a damp hot towel test on the hoses to see if they are leaching, and if they are I will replace the hoses. The only other options, as far as I can make out, is to fit an inline vent filter and or have a new tank made.
The plugs I bought for blanking the tank were 1-1/2Ē BSP, not thinking about the tank being American. When I went to fit them they kept wanting to go in skew whiff which makes me think the tank bosses are NPT, does anyone know for sure if this is the case.
Finally, I need to reseal the hose tail threads back into the threaded bosses which are welded to the tank. Iím not sure what sealant to use here. Iíve spoken to Sika Sealants and they havenít got anything which will bond PVC-u to polypropylene. They say that you canít bond to polypropylene. Now Iím guessing the blue Sierra hose tail fittings are made from PVC-u and that the holding tank is made from Polypropylene. Does anyone know for sure if this is the case or otherwise, and does anyone have any sealing suggestions other than PTFE tape.
For interest Iíll try and post some pictures of the tank in question. Thanks.