Holding tank opening

Hi all,
Been lurking here for quite some time, absorbing advice, etc. After a dozen years, I sold my Cape Dory 28 trawler and bought a Legacy 34 flybridge. Not quite a trawler, but... maybe I can still get help here?

I have an issue with the holding tank that I don't understand. Viewed from the top, there are two cylindrical recesses. The one on the left in the picture is the tank watch sensor. The one on the right is just open, and something is obviously wrong here. Liquid waste seeps into the opening from the bottom, and the smell of course escapes into the boat. Down inside that opening, it appears there is some kind of tube/pipe running horizontally, plus it appears there is some kind of foam (possibly the expanding spray-in foam). All of this saturates with waste. For the moment, I taped plastic over the opening to help contain smell.

What is the purpose of this opening? Should I just seal it up?

Thanks for any advice.

Joe

Most holding tanks have (or should have) a clean out or inspection port. Looks like a glued on cover fell off? I would seal it for now. At some point install a new one.

I am a little confused about the plumbing. Most tanks fill from the top, empty from the bottom. Any evidence a previous owner fiddled with the hoses/piping?

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First welcome aboard. Maybe the PO had a tank aeration system installed in the tank. How big are the tubes you saw down inside the tank? They may be bubbler tubing for air distribution. The opening absolutely needs to be closed up. There is a company that sells plugs for tanks that Peggie Hall recommendations. I don’t remember the name of the company but Peggie will probably chime in on this thread so she can let you know the company. Did you mean that there is foam down inside the holding tank?

Hey, thanks for the replies. Some clarifications:

This is not simply an opening cut in the top of the tank. It is actually a cylinder, with an inner wall. I'm not sure if it goes all the way to the bottom of the tank, but I do not think so.

Not sure about modifications. Based on the cut made to the support structure in the picture, I suspect the tank watch was added after installation. The inlet to the tank appears to be near the top, on one side. The outlet goes from near the bottom out to a Y-valve for overboard vs. deck pumpout.

The little tube in there is narrow, maybe half-inch tube. You can see it (barely) in the picture. Aeration is an interesting thought; not sure what else it could be for.

This issue was not called out in the survey, but the tank was empty at the time. I reached out to the surveyor as well.

It looks like the left side level probe might have been relocated by a PO. The reason I say that is the location relative to the hold down and it looks like a DIY mod.
Does the seal at top look like a factory plastic weld or other sealant caulk?

It looks like a molded in baffle which has perhaps sprung a leak. Larger plastic tanks normally have molded in baffles and they look just like that.

If that turns out to be correct you could buy an "add a port" kit and use it to seal that opening.

Ken

I'm not often stumped, but I don't have a clue what that is, nor what all the glop in the bottom is or what that pair of wires might have been connected to...I've never seen anything quite like it. I don't suppose the PO is available to answer any questions about it?

Just closing up the hole is easy...and it looks as if there's been a typical inspection port installed in it. Beckson makes top quality in all sizes...Defender has 'em: Beckson inspection ports Installation is simple: the cap (a rubber o-ring seals it) is threaded into a flange that's secured to the tank with screws, sealed with a rubber gasket...no need for all that glop that was used to secure the tank level indicator.

If possible the tank needs to be completely cleaned out, 'cuz it's definitely reducing the tank capacity and if it's capable of dissolving can clog up the discharge. If that's not possible--or more trouble than it's worth--consider replacing the tank. Ronco Plastics Ronco Plastics marine Tanks is your best source...They make TOP quality thick-walled water and waste tanks for a very reasonable price and have more than 400 shapes and sizes, over 100 of which are non-rectangular, and they install fittings in the sizes and locations specified by the customer when they make the tank.

A tank level indicator that has senders attached to the outside of the tank will be an improvement on whatever is there now. The Profile system is the best and reasonably priced Profile Tank Monitors

And if the tank is any indication of the age/condition of the hoses, I'd replace those whether you replace the tank or not.


--Peggie

I stumped Peggie!! :-O

My operating assumption is same as Ken, that this is some kind of molded in baffle. I vaguely have this notion that I've seen something like that before in some kind of plastic tank, where there is a rod (almost like a lifting handle) inside a recess like this, but I can't quite put my finger on it.

The wires I think are just going to the tank watch light. The tank full indicator light looks exactly like this one.

I think next step is to (ugh) really get in there and try to clean it out and see if I can learn anything else. Then as long as it is not leaking below as well, I can try to seal it off for now and maybe replace the tank (and hoses) in the off season. I duct-taped some rubber gasket material over it already, and the smell is dramatically better in the boat already. So I think I could live with that for a couple months if need be.

I stumped Peggie!! :-O


Yup...you did! It doesn't happen often and at least I've proved I don't try to bluff when I'm clueless! But I'm NOT stumped by the Tank Watch! It's a TW I (at least the panel is...who knows whether the sender still is), which is supposed to light up when the tank is 3/4 full (which puts in compliance with USCG regs but that's all), but the sender is so short that it actually only lets you know when the tank is about one flush away from overflowing out the vent. It's been discontinued, btw. And now I see the two white wires coming off it, which would be the original wires. I'm guessing they weren't long enough, which could explain the red and black wires. When you finally get the internals of the tank sorted out (and can tell me what the heck they are!), you might consider replacing it with one that provides 1/4, 1/2, 3/4 and Full readings and uses senders that go on the outside of the tank.



--Peggie

Below are the foil senders on the outside of my tank, and the readout panel mounted on the sink cabinet.

I have some answers! And still some unknowns. I had to open up a lot of panels and pull stuff apart, but I got some visibility around the tank. The cylindrical opening is NOT open to the inside of the tank. It goes all the way through to the bottom. The foam stuff was used under and around the tank to pad and secure the installation. The tube down in there is basically just a weep hole connecting a sump area forward of the tank with one aft, allowing water to drain aft to where there is a pump. It is beneath the tank, not in/through it. This all makes a lot more sense. I flushed the whole area with water and KO thoroughly several times and now I've let it dry out really well, and the smell is dissipating quite a bit.

The unknowns: where did the waste come from, and is it going to happen again. I filled the tank to the top, and water came up through the tank watch cap, and ran down the hole and down the sides of the tank. So perhaps this is what happened, and I just need to figure out how to seal that tank watch sensor, and be diligent about not overfilling. Not sure if the hole kept filling back up because the whole area was wet/saturated or standing waste water was down there. It's kind of hard to believe the tank is cracked or broken underneath, but I guess it might be. One next step is to get the vent hose off of there and find out if it is clogged.

Joe

Best bet is "be diligent about not overfilling". I'd also look to rig up some sort of way to keep that spot from getting filled again. But if it provides an inspection port of some sort I wouldn't block it permanently.

If the foam gets saturated/infiltrated it will never be free from stink. Remove anything suspect. Which may then turn this into a job fraught with other "while you're at it" complications.

Sounds like you are making progress Joe. Interesting setup. Not sure I understand it, but you are figuring it out.

The tube down in there is basically just a weep hole connecting a sump area forward of the tank with one aft, allowing water to drain aft to where there is a pump.
A tube INSIDE the holding tank that's just a "weep hole???" Water from where??? If it's from inside the tank, it's not water, it's sewage!

I flushed the whole area with water and KO thoroughly several times and now I've let it dry out really well, and the smell is dissipating quite a bit.
Pick up some PureAyre (available from pet stores, Walmart, Amazon and just about everywhere else) and spray a fine mist of it onto/into every surface, nook and cranny of that area and then just let it dry. That should get rid of the remaining odor completely.
--Peggie

HeadMistress said:

The tube down in there is basically just a weep hole connecting a sump area forward of the tank with one aft, allowing water to drain aft to where there is a pump.
A tube INSIDE the holding tank that's just a "weep hole???" Water from where??? If it's from inside the tank, it's not water, it's sewage!

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No no, it's below the tank. I think the tube was installed to weep water aft, and then foam was used to secure the tank installation (and hence, the foam is all around the tube below).

Thanks for the PureAyre recommendation; I'll give it a go!

Glad you are getting a handle on the problem. Good luck.

wkearney99 said:

Best bet is "be diligent about not overfilling". I'd also look to rig up some sort of way to keep that spot from getting filled again. But if it provides an inspection port of some sort I wouldn't block it permanently.

Click to expand...

It is possible that I am the culprit that overfilled it.

I thought the breaker for the head only had to be on if using the electric pump connection. I had been manually pumping, so I didn't turn it on. Turns out the tank watch indicator does not light up either, if the breaker is off, so I may have overfilled and didn't know it. Or who knows, maybe the prior owner did it too...

Joe ..not sure if you ever figured it out ,but to me it looks like somebody has tempted to make a pressure relief valve that opens if the tank is blocked from vent air when pumping out from a dock pump out system ..there is a fitting from sealand that actually fits in that cut out is my guess. It is called a pressure relief valve

Hello there if you have not yet settled this problem it is a pressure relief valve. that should be in there. They are put in tanks for when pumping out at a dock, if the tank vent is plugged, it will allow air to prevent the tank from exploding or being damaged. It has been blown out and would be lying in the bilge somewhere. It is a simple easy simple easy repair by pushing a new Sealand pressure relief valve, back in it with the grommet that you need to do this

I forgot to include. make sure you check your vent for proper airflow . And what you should be doing annually with every tank vent