Fixing Holding Tank Fitting
- Thread starter tgotch
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lwarden
Guru
I'm presuming this is a rotomolded polyethylene tank. I would try cutting the old one off and shaving it down flat. Then bond on a flange such as this
alscoplastics.com
with 5200 and some 316 SS Plastite screws (available through McMaster Carr. 5200 doesn't bond to polyethylene very well, but should be good enough with the screws doing the mechanical work.
PVC Schedule 80, Flange, Threaded, 1/2 in. to 4 in. Sizes
PVC Schedule 80 fittings are for use with chemical processing, industrial plating, chilled water distribution, deionized water lines, chemical drainage and waste water treatment systems.Standards and Specifications:NSF Standard 14 and 61ASTM D 1784 - MaterialType IV, Grade 1 (cell class...
alscoplastics.com
That appears to be part of a thread-barb hose fitting that's missing the hose barb. What appears to be melted plastic around it is melted plastic: the spinwelded female tank fitting that it's threaded into. You should be able to unscrew it to remove it...in this case it shouldn't matter if you crack it further. Just be careful not to damage the female tank fitting. If it's glued in, you may have to cut it off flush with the female tank fitting so you can plug it and create a new vent fitting using a Uniseal and a short piece of sched 80 pvc.
Replace it with a thread-barb hose fitting (threaded at one end to go into the tank fitting with a smooth or barbed end the hose goes onto) that's the correct size for your vent line (5/8" is the standard size) Be careful not to over-tighten it...you're lucky that only the the threaded male fitting cracked and not the female tank fitting.
I'm available for questions.
--Peggie
Replace it with a thread-barb hose fitting (threaded at one end to go into the tank fitting with a smooth or barbed end the hose goes onto) that's the correct size for your vent line (5/8" is the standard size) Be careful not to over-tighten it...you're lucky that only the the threaded male fitting cracked and not the female tank fitting.
I'm available for questions.
--Peggie
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Comodave
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5200 won’t stick to the plastic tank. You want an Elastomeric caulk by Rule. It will stick to the tank. But the Uniseal is fantastic. If needed I would overdrill the hole for the Uniseal if you have to. Then step the pipe down to fit the vent hose.
Sorry Dave...I would not do that or anything else that requires splicing hose. However, I do recommend "upgrading" the vent line to 1". That would require replacing the thru-hull with an open bulkhead (aka "mushroom") fitting 'cuz "vent" fittings are only available in 5/8". The open thru-hull has a couple of advantages: 1. it allows more air exhange with the gasses in the tank, which helps to prevent odor from occurring...and 2. makes it possible to prevent vent blockages by putting a hose nozzle against it to backflush the vent line every time you wash the boat or pump out. Anything that's tried to set up housekeeping in it will just get a water slide ride into the tank.
Holding tanks also require a little maintenance....they should be rinsed out 2-3 x season--or every2-3 months if you're a liveaboard or use your boat year round- to remove sludge. It's not hard to do....just put 4-6" of water into the tank VIA THE DECK PUMPOUT FITTING 'cuz it enters the tank at the bottom to stir up any sludge and hold it in suspension so it can be pumped out. Pump that out...repeat..repeat till you're pumping out clean water. If you have a macerator pump to dump the tank, do it one more time with the macerator pump running to clean out its plumbing. Macerator pumps should also be rinsed out after every use 'cuz waste is sticky and can cause the impeller to get stuck and crack a vane.
--Peggie
Holding tanks also require a little maintenance....they should be rinsed out 2-3 x season--or every2-3 months if you're a liveaboard or use your boat year round- to remove sludge. It's not hard to do....just put 4-6" of water into the tank VIA THE DECK PUMPOUT FITTING 'cuz it enters the tank at the bottom to stir up any sludge and hold it in suspension so it can be pumped out. Pump that out...repeat..repeat till you're pumping out clean water. If you have a macerator pump to dump the tank, do it one more time with the macerator pump running to clean out its plumbing. Macerator pumps should also be rinsed out after every use 'cuz waste is sticky and can cause the impeller to get stuck and crack a vane.
--Peggie
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been lots of good feedback on this. my thought would be that if the broken adapter fitting won't spin out of the tank threads, or breaks while trying, get the next size up pipe tap and tap drill and put new threads in the tank. then it's an easy process to adapt back to the existing vent hose, or upsize the vent line to match the new fitting.
tapping plastic is really easy to do.
Comodave
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I was not suggesting splicing the hose. I may not have been clear. I meant that if he had to go to a larger Uniseal due to the old tank fitting being damaged then he coule use a PVC fitting and reduce the size to match the existing vent hose. I agree that the larger vent hose is better. I upgraded my vents to 2 1.5” hoses, one from each side of the boat. Now there is excellent ventilation in the holding tank.
