Holding Tank Gravity Discharge Pipe

[Basil]

I am thinking of trying to replace the discharge pipe beneath the holding tank. On my boat it has a big red handle that I swivel to open the tank and discharge it. My problem is that I cannot get my holding tank to pump out beyond 1/4 full. I used SEW Clean and tried to eliminate any calcium buildup. I have also shoved a mop handle inside there from above it on deck and swished it a bit (though this is constrained by the width of the deck cap). I have no access port to open and see if calcium is causing this issue. Other than replacing the tank, my thought is to remove the gravity pipe, scrape things out as best as can be reached, and then perhaps replace that lower pipe if it is calcified as well. Anyone else ever struggled with this issue? If so how did you handle it? (I am not talking about the joker valve and the tank input hose which I have replaced a number of times due to calcification - this is discussed in this forum. I have not seen any discussion about the gravity hose). Thanks.

[KenKrawford]

Barry, one other thing to check is the tank vent. It's located on the outside of the hull adjacent to the tank. If it's clogged you'll have a problem filling and emptying the tank. The valve on the bottom of the tank is for overboard discharge only and replacing it won't have any effect on problems associated with pumping out.
Like you, I became concerned about solids that might accumulate in the bottom of the tank. I considered a device like this - https://www.amazon.com/Valterra-A01-018 ... 990&sr=8-8 but the diameter was too big for the deck fitting and I ended up making one from PVC and a few other plumbing fittings. It works quite well.

[Basil]

Thanks Ken,
I will give this a try.
..barry

[Bob_A]

Barry,

Having the same issue with discharge I just completed the fix.
I removed the Holding tank and brought it home where I removed all fittings and pressure washed the inside to totally clean.
I would say up to 10 lbs. of calcium carbonate came out.
This enables one to really inspect the fittings which can be an issue too.
I suggest you go on the Catalina Direct site and look at the drawings of the Holding Tank. You'll see right away why a broom stick wont do a thing.
I tried all this too. The deck fitting and associated pipe to the bottom are offset to the discharge which makes rodding pretty much useless.
I really like Ken's idea for the 90 degree wash fitting. If a guy were to make something like this to attach to a pressure washer wand then you'd have a very excellent chance to blast out the calcium carbonate. This wont give you access to the fittings esp. the discharge but a huge help.
At the dock I blasted down the deck fitting with a hose and beat on the tank to no avail. Or some avail but not enough.
The good news is our Ronco tanks are very robust.
I can tell you that after 16 years the ball valve and associated fittings including discharge hose were not too bad. The least of your concerns should be the discharge hose under the ball valve as this does not have effluent sitting in it as it just passes through on the way out. The length of exposed inside surface of the hose between the two fittings is only about 1"
I could not find suitable chemicals nor could I find one pro near here that knew of something that would work or who endorsed that method. But I remain very interested in this.
Going forward I will rig up the hose fitting per Ken and rinse out regularly. We have an alternate freshwater flush which helps the prevention of the calcium carbonate build up. At the least I recommend keeping the tank empty as much as possible and using the toilet bowl to flush fresh water up and into the tank. And yes, check your vent. pluck out the bug screen at the opening if its still there and blast water down the vent when hosing the hull.
If you or anyone else wants detail on the re & re of the tank, just let me know. Its a bugger.
Good luck.

[Bob_A]

Barry,

Having the same issue with discharge I just completed the fix.
I removed the Holding tank and brought it home where I removed all fittings and pressure washed the inside to totally clean.
I would say up to 10 lbs. of calcium carbonate came out.
This enables one to really inspect the fittings which can be an issue too.
I suggest you go on the Catalina Direct site and look at the drawings of the Holding Tank. You'll see right away why a broom stick wont do a thing.
I tried all this too. The deck fitting and associated pipe to the bottom are offset to the discharge which makes rodding pretty much useless.
I really like Ken's idea for the 90 degree wash fitting. If a guy were to make something like this to attach to a pressure washer wand then you'd have a very excellent chance to blast out the calcium carbonate. This wont give you access to the fittings esp. the discharge but a huge help.
At the dock I blasted down the deck fitting with a hose and beat on the tank to no avail. Or some avail but not enough.
The good news is our Ronco tanks are very robust.
I can tell you that after 16 years the ball valve and associated fittings including discharge hose were not too bad. The least of your concerns should be the discharge hose under the ball valve as this does not have effluent sitting in it as it just passes through on the way out. The length of exposed inside surface of the hose between the two fittings is only about 1"
I could not find suitable chemicals nor could I find one pro near here that knew of something that would work or who endorsed that method. But I remain very interested in this.
Going forward I will rig up the hose fitting per Ken and rinse out regularly. We have an alternate freshwater flush which helps the prevention of the calcium carbonate build up. At the least I recommend keeping the tank empty as much as possible and using the toilet bowl to flush fresh water up and into the tank. And yes, check your vent. pluck out the bug screen at the opening if its still there and blast water down the vent when hosing the hull.
If you or anyone else wants detail on the re & re of the tank, just let me know. Its a bugger.
Good luck.