Access port in holding tank

[Set2sea]

Seeing how the holding tank is basically immovable due to the bulkheads, it is difficult to know if it is caked with crud on the bottom! I expect it is. I bought a 6" beckson port for inspection and cleaning. Before I go into this task, I would like to see if others have done so. On my last boat, I had in inspection port, but I could also lift up the tank to fully empty.

[Phil Spicer]

   Paul,
Did the inspection port many years ago. Called the tank company about what sealer to use. They told me "DAP" gutter seal. have done both holding and water tanks.
When you do the holding tank, do it on a windy day...

[Fred Koehlmann]

Hmm, unless you had a holding tank with the "drain" at the bottom at the lowest point (i.e. under the tank), I would suggest that it is physically impossible to completely drain any type of tank, let alone a holding tank where the heavier bits can settle to the bottom. Even then, the hose would sill have stuff in it. I would propose that all our tanks all have some "crud" on the bottom. As to how "caked" on it would be, would depend on the nature of the tank surface, how often you pump out and how well you pump out. During the sailing season we try to pump out every weekend. And when we do, we also flush fresh water in through the vent as the attendant is sucking out at the other end (out vent is at the forward end of the tank and the outlet at the aft). This works for us because it flushes the length of the tank. The attendant can also see when the color changes of what they are sucking out (they've got a short clear bit in their hose). At the end of the season we flush it several times and then with some anti-freeze. I've known people to take their boat into the waves just to "rock" it for a bit before doing the final suck out.

I've heard of some people having an access port to their holding tank, but I wonder about the logic behind it. I personally would want to minimize the number of potential openings/outlets in this particular type of tank. I really want the stuff inside to stay there, and I have no interest in interacting with it. I guess we've also never I my fifty years boating had a boat with an access port to the holding tank. I know I've never had a reason to get into it, nor do I remember my dad ever needing to get into it. So I guess I am wondering why people want to get into it?? If its cruddy inside, so be it. It's a holding tank!

You mentioned that you were able to lift up your old holding tank. I'm surprised and a bit concerned. Your holding tank should be fairly well secured. The last thing you want when sailing in heavy seas, or get caught in a knock down, is to have your tank knocked about and potentially spill its load! Personally, I would make sure its went tied down and immobile.

[Indian Falls]

There isn't much holding that bit of plywood aft of the tank to the hull.  I removed mine and did not put it back in.
 
In my opinion the task at hand: crud in the bottom of the tank, does not have a maintenance schedule that warrants cutting a hole in the tank
and having yet another point at which smells can emanate into your saloon.  

I also recommend removing the tank for a thorough pressure wash inside and out.  Where you can then paint the compartment with bilge coat, I painted the tank with plastic primer and oil alkyd rustoleum.  I found the source of stench from my tank was actually the compartment, not the tank.  I used ballistic nylon strap and two screws to hold the tank against the forward bulkhead.  

On a lesser note, you don't want to do that cleaning operation inside your boat... you'll wish you'd removed it about 5 mins into it.  

Make sure you get enough thread sealant and don't use tef tape, just don't. Use a greasy, flexible, non drying type of pipe thread sealant.  
Plastic fittings cannot produce the pressure needed to make tef tape effective.  If you achieve this you will split your fitting.

Hope that helps!

[Stu Jackson]

You could also simply take your vent hose fitting off and look inside and see what's there.  Before you engage in more destructive installations.

[Jeff Tancock]

Am I the only one that can't stop chuckling? What do you think is in there? Go ahead......surprise me.

[Set2sea]

The reason I am contemplating this is so I could reach in and clean the tank. Believe me I am gagging just writing those words. At least start out with a clean tank. I took ownership of the boat last year. All the lines to the tank were caked which I replaced. I would get a horrendous stink when flushing. I just replaced the vent hose, see what that does. The thinking is this - I can't imagine it would stink as much as it did last year with a clean tank. I didn't learn about the fresh water flush until the off season. Judging by other things on the boat, I can't imagine the PO ever cleaned the tank.
I am going to look at removing the bulkhead once more.

[Stu Jackson]

Paul, I trust you may have read the "101 Topics" about head odors.  It covers the vent smell quite well.  Often the lines can be clogged while the tank remains just fine because of the sloshing of the contents.  I still recommend checking before dismantling.  Good luck.

[Indian Falls]

I just went through the 101 topic on odors... lots there, but not about the vented gas from the stantion vent.
The only thing I found that reduces that odor is lots of that blue stuff for RV holding tanks.  Or only use the head on the "POTTY TACK" so the wind won't carry the expelled gas through the cockpit.  I've been tempted to move my vent to a through hull below the rub rail but it seems like a lot of work for 50/50 chance you won't smell the gas in the cockpit.

[Wayne]

When someone flushes water goes into the tank and displaces air which comes out the vent.  Nothing is going to change that.  I moved my vent forward and below the rail (the new vent hose goes into the port vberth locker and out).  Odor still wafts back to the cockpit when someone flushes.  I'm using Odorlos?  Odorless?  Something like that, and it helps.  A couple of years ago I installed a tank sensor.  I forget the brand, but it is one of those things that has three little floats that extend down into the mucky goo.  A hole 2" to 3" in diameter was needed through the top of my tank, with a screw in fitting of the same diameter.  This sensor has proved to be one of the best livability improvements I have made--no more guessing how full the tank was.  They aren't terribly expensive.  If you are going to cut a hole into your tank, might you consider a 'two birds with one stone (or hole)' approach?

[Stu Jackson]

I just went through the 101 topic on odors... lots there, but not about the vented gas from the stantion vent.

Head Odors 101.2  The Difference between KO & Odorlos  (scroll up to Reply #2)  http://forums.catalina.sailboatowners.com/showthread.php?p=890493&highlight=odorlos

This is in the wiki, too:

http://www.c34.org/wiki/index.php?title=Marine_Sanitation_Fact_and_Fiction

[Footloose]

I have thought about putting the vent 10-15 ft up the mast to keep the odors off the deck but have not figured how to do it and keep the vent hose going in an upward direction and not have to step over it or duck under it.

[Indian Falls]

Dave, try this instead of going up the mast with your vent:

I screwed a fitting into the hole in my stantion and put a 3/8 vinyl tube over the side a few inches above the water.
The gasses escaping the tank when the head is flushed tend to stay low and out of the reach of crew and passenger nostrils.  Take the hose off when you leave the boat. 

I also found that I needed a shot of great stuff up inside the stanchion above the vent to stop the gasses from exiting where the lifelines go through.

[mregan]

I relocated my vent to a thru hull located below the rub rail.  While underway, we don't get a blast of odor when someone uses the head.  Usually it's worse at anchor if someone is using the head.

[Andrew Harvey]

When we purchased our boat the holding tank was quite pungent. Rather than replace with plastic , i replaced with stainless steel.
No more odours at all.
I will not get in to too many details about removing the old tank.
I agree with others .. you do not want to be sticking your nose in there.