trouble pumping out: pick up tube problem

[DEast]

I've read all of the posts about pump out and have found our issue seems unique so wanted to post.

2003 hull#20
purchased 2025 from original owner

Issue: We've always had a difficult time pumping out the black tank; it would pump, but ridiculously slowly. Two main issues other's have discussed; poop pyramid/calcification and air vent obstruction. Accessed the vent, disconnected, and assured it was clear. Used a LOT of tank cleaner over months without help. It just seemed like something was occluding the bottom of the tube (you could pour water into the top of the pump out fitting and it wouldn't drain into the tank, or would drain slowly after hours). Looking at the factory schematics, the 1 1/2" tube has a 45 degree cut at the bottom, so it seemed the occlusion must be large.

Diagnosis: After flushing and clearing out the tank and pick up tube, I used an inspection camera to send down the pump out tube to discover what was occluding the bottom. To my amazement, the tube does NOT have a 45 degree cut at the bottom. The bottom of the tube is flat and sits flat against the bottom of the black tank leaving a ridiculously thin sliver of space. I would imagine the pipe was installed like normal without being cut first and this issue must have been occurring since the boat was brand new.

Questions: Has anyone else discovered this issue? What did you do about it?

Potential Solution: What I'm planning to do is buy a 3 foot long 1/4" threaded rod to use like a drill bit. I'll attach a small circular blade to the bottom (sandwiched between two nuts) to send into the pickup tube along with the camera and cut a notch in one side of the bottom of the tube. The blade only needs to cut plastic, so a modified dremel disc could be used (regular disc diameters are too wide for the tube). Also considering buying a somewhat soft metal washer (perhaps 3/4" diameter) and using the dremel to notch a cutting surface along the edge of the washer. I should be able to send the rod with camera to the base of the tube and, with the 1/4" rod in a drill, carefully cut one side of the tube enough to allow proper pumping.

Concerns: Don't cut the tank! Having the cutting blade about 1/2" from the tip of the rod should mitigate cutting the tank. Using the camera should be helpful to guide the careful process. I thought about just cutting 1/4"-1/2" off the bottom of the tube, but that would leave a ring of plastic in the tank that could occlude or jam the ball valve in the gravity drain tube in the bottom of the tank. This is why I think notching out one side should work better to keep from having to remove the ball valve tube to retrieve any cut material. For any debris left in the bottom, I plan on using a shop vac to clean the tank after the cutting project. I've found that a length of garden hose duct taped to an old shop vac hose works well to send down the pick up tube for clearing it out (what I did before inspecting with the camera).

I'll take some pictures of the process and can hopefully post them later as a follow up.

David
90 Degrees

[KenKrawford]

David you certainly have an interesting and hopefully unique problem. I think your solution is a viable one but one other thought to consider. I'm assuming the tank is empty and the ball valve is closed. If the rubber hose between the dump valve and the overboard discharge tube is still connected, consider removing the hose. With a bucket under the ball valve, slowly open the valve and remove any remaining material from the tank. Then use your inspection camera thru the valve and see what things look like from the bottom of the tank. If the camera doesn't give you a good view consider removing the valve as well. If the pump out tube is truly that close to the bottom of the tank I'd be in favor of shortening the length of the tube rather than notching it. That way the cut piece of the tube could be removed via access thru the ball valve.
Let us know what you end up with.

[DEast]

To follow up, over the past few months I attempted several variations of a long threaded rod down the pump out tube with a small circular saw blade on the end. Attached to a drill I could begin cutting the bottom of the tube. The shot from top to bottom, however, is not perfectly straight, so I was able to cut one side of the bottom of the pump out tube, but not all the way around. I was unsuccessful removing a section of the bottom of the pump out tube.

From there it seems the only way to get the issue resolved was to access the bottom of the pump out tube from the inside of the tank.

I removed the shelf above the tank and had pretty good access to the top of the black tank. I decided on the dometic tank inspection port and cut the appropriate sized hole in the top of the tank. You'll want a 90degree drill adapter since there's very little clearance above the tank for a bit and drill. Once the hole was cut I hosed out and shop vac'ed out the tank. There was quite a bit of scaling on the sides built up that I addressed with a scraper. I'm hopeful this makes my SeaLevel II tank reader more accurate. Once things were cleaned out and sprayed with disinfectant (multiple times!), I was able to try to address the bottom of the pump out tube. I installed the dometic inspection port AFTER the work as it gave me more room to shove my arm into the black tank (...buy a boat they said... it'll be fun they said...).

For this step I used a dremel with the same small circular saw blade I tried from the inside of the tube. I was basically to the top of my bicep into the tank to get the dremel to the bottom of the tube which resulted in some minor bruising for a few days. This part you have to be patient with; despite the desire to make the "arm in the black-tank" situation go by more quickly. You're working blind and by feel alone, so orient your hand, start the dremel, cut a bit, then feel around and do some more. The main issue is making sure you're cutting the tube and not the tank. On the back side there's VERY LITTLE room at all, so this is when being patient comes in. I was able to cut about about a 1/4 - 3/8" tall notch into the bottom of the tube. I was not able to completely get around and cut the back of the tube due to the close proximity of the tank wall. I was able to get about 2/3 of it opened up.

With that done, I installed the dometic inspection port... I won't go into that detail since there are probably other forums discussing it, but I followed manufacturer instructions and used the recommended Permatex #2 gasket forming sealant. I accidentally dropped one of the nuts and washers into the black tank in the process and used the shop vac to retrieve them. I also used it to remove the plastic bits from cutting the tube and drilling into the top of the tank to make sure there wasn't any debris that might later make issues with the ball valve in the bottom of the tank.

Removing the shelf was another issue... I essentially had to cut it up and destroy it since it was installed around the standing rigging rod that runs through that cabinet. With the dometic inspection port on top of the tank, the shelf would've been too thick and stood proud anyway. I got some 3/8" laminated material from Lowe's and used that. There are small wooden bits screwed onto each side of the cabinet to support the shelf, so I had to move those up to clear the inspection port. The shelf I made is two parts; a section on the right (to the right of the rod supporting the standing rigging) is screwed in and permanent. The larger section to the left is removable in order to access the inspection port. It turned out quite nice and I'm happy with the way it looks. It's also nice having an inspection port to address any future issues with the black tank. It's also nice knowing the tank has had a proper scrubbing and scraping.

I'll see if I can put some pictures on a .pdf and upload those to the forum for reference.

David
90 Degrees

[DEast]

I cannot downsize the images small enough to post. If you'd like, just message me and I'm happy to send a .pdf with some images of the project.

When reviewing my previous post, I think the notch I cut in the bottom of the pump out tube was more like 1/2 - 3/4" (based on my memory of the space around my finger as I probed around the cut).