Plastic Classic Forum

I've been working on this thing for too long, I'm tired of the oh-so-official term "holding tank". It's a box for poo, I call it the Poo Box.

Between tasks over the winter I knocked this together with scraps of ply and cloth and resin leftover from whatever else I was doing at the time.



Except for the pitched bottom, it uses all available volume behind the head between the bulkhead and the chainplate knee. I should probably actually test the capacity before installation. It was months ago that I did the math, but I think it's in the neighborhood of 10 or 11 gallons.

Why did I bother to paint the poo box? I've no idea.



The pumpout fitting will nipple directly to the dip tube. This leaves juuuuust enough clearance atop the tank for the inlet and vent(s).

That's where I stand at the moment, pressure-tested and ready to go.


I still need a bit of a support ledge, but beyond that it's just a bit of piping and I'll have that opiate Sense of Accomplishment.

You've gotta love the Henderson pump on the Lavac: Head pump, holding tank pump, potential bilge pump and toilet-paper holder!

Nice Poo Box.

R.

Is it not also a Pee Box? Shouldn't it rightly be christened the PooPee Box?

Yeah, that's what y'all get for allowing me to post on the forum at 0100...

Figment wrote:I still need a bit of a support ledge...

You need more of a support group, methinks!

Is it not also a Pee Box?

Anyone that sends pee to the poo box clearly is not of sound mind.

-Britton

Nice work, Mike. I've got a similar project in the works for my boat.

To date, though, all I've done is to cut each of these in half:


That gives me 4 panels that I can then cut up further as necessary to make into the sides, top and bottom of my "PooPee Box" which will fit in against the hull under the deck in a location similar to yours.

Regards,

Tim A.

Recycling! I love it!

I wish I'd just done mine in all flat-panels. That compound-curved back, though it gained perhaps two quarts of capacity, was an unworthy complication.

Yeah, I found the more detailed and complex in my tank shapes the smaller the real return in capacity.

You know, I really thought I was on to something great by going to stainless steel construction. The lack of imitators is making me wonder just how silly I have become in the last few years...

-Britton

I've always heard that the acids in the contents of the black water tank presented a reaction problem with stainless steel, which is why they're usually made from plastics or fiberglass.

Anyone have solid information on this?

I heard the same rumor. I think the 'Queen' mentions this.

When I discussed this with the tank builder he said there might be a slight degradation due to corrosive action but the side panels are excessively thick to counter it. He has made a lot of waste tanks and has not seen a real problem with it. Then again he wants to sell me a tank...

In any case, I don't intend to use the tank much and will flush it regularly as a precaution.

-Britton

I had a Stainless holding tank onboard that had a weld failure. I won't be doing THAT again! I realize that CheoyLee is not renowned for their metal work but I think that SS is poorly suited to be a holding tank.
Best regards, David

It seems to me that holding tank failure is something that's best to only read about, not experience...

Tim wrote:It seems to me that holding tank failure is something that's best to only read about, not experience...

I'm not sure it's even good to read about...

Well, I certainly hope I won't be pulling this tank out in a few years. I didn't make it easy. (where was all this opinion when I was asking last year?...)

I agree that stainless steel in this application warrants some caution. Perhaps some of the different opinions come from the fact that the skill of the welder plays a large part in determining the final product. Heat, thickness, impurities, etc. are all function of the skill of the welder and if not done correctly can quickly lead to trouble.

Ultimately, I went with stainless on the builder's recomendation/experience, the fact that he was building several other tanks for me and the jobs were lumped together, and the idea that stainless does a pretty good job of stopping odors. For all I know fiberglass and plywood might hold odors well but in my imagination I can see 20 years of use possibly leading to an odor problem. I don't have any real experience to back this up though. Just a hunch. Of course for the cost differential it would be easy enough to replace a fiberglass tank several times before it equaled the cost of stainless.

There must be an additive that would counter the acidity of the poo box contents right?

Anyway, sorry for highjacking Mike's thread.

I like the tank and location and could easily have chosen that route as well. I am surprised you got so much volume though. I guess I was thinking 6-8 gallons was about all one could squeeze back there.

And I missed the toilet paper holder. Pure genius :-)

-Britton

Would you believe I've had a tricky-cool Oceanaire Dryroll paper holder sitting on the shelf for about three years now? That convenient holder will probably become less convenient when I move the pump lower on the bulkhead in the plumbing reconfiguration.

Just for the sake of nerdery, I filled the box with measured gallons of water yesterday. Full capacity is a touch over 13 gallons, but practical capacity is probably 10, as any more than that will almost certainly foul the vent lines while sailing.
Of course this will vary triton by triton, as the location of that chainplate knee varies.

That's right, my poo box has greater capacity than my fuel tank.

Does anyone know the gallons-per-flush of a Lavac off the top of their head?
(HA!)

Wouldn't a bit of baking soda solve the acidity problem? I'm no chemist, but that stuff seems to be the cure-all.

Figment wrote:Does anyone know the gallons-per-flush of a Lavac off the top of their head?

3 pints.

dasein668 wrote:...3 pints.

Somebody cue the beer joke!

:-)

I measured the capacity of the tank I built for Kaholee, and it was 10 gallons to within 3/4" of the brim.

Here we are today, in place and secure, waiting for me to play plumber.



The support is just a glassed-in chunk of 2x4, but man I got the location SPOT-ON because it is one squeaker of a fit. The retainer strap, to which I devoted entirely too much thought, is hardly necessary. I bought a battery strap for the purpose, but of course it was just a bit too short, but I had this snappy sail-tie in the drawer that I just never ever ever use... It'll do.

Plumbing complete.
It all looks so lovely, I might forego the panel replacement.

That looks really nice Mike!

Nevermind. Must replace that panel ASAP.

Looking at that pic earlier, this thought crossed my mind: jeez, I'll bet there is enough space down there for another Y-valve that I could connect to the bottom of the tank for overboard-pumpout...

bad bad bad ideas. Must replace that panel ASAP before any more bad bad bad ideas take root.

hehe, you are a better man than me Mike :-)

-Britton

dasein668 wrote:That looks really nice Mike!

The only place I know where someone can post a picture of their commonde and get a compliment like that! :)

An unanticipated flaw in the masterful plan of locating this behind the head?.. NOISE.

The water splashing to the bottom of the box on the first test-flush was pretty friggin loud. Not exactly the subtle ?it just goes away, you needn?t care about where? experience that The Ladies are after. I think I?m going to have to figure out some sort of acoustic blanket arrangement before I enclose it behind the panel.

If it ain't one thing...

I don't see a lot of sense in rigging a 10 gallon tank to pump overboard. It's so small to begin with that you'll be required to have it pumped out frequently; it can't hold enough to become an inconvenience that you'd suddenly find a need to pump over the side.

If you're somewhere without pumpout facilities, and would therefore consider pumping your tank overboard, save a step and just pump the head overboard in the first place.

I sail in an area where I can easily get out of the no discharge zone (more than 3 miles out). When ever I do I pump out my tank (14 gal.) almost regardless of how full it is. Its just easier. I don't have a wye valve from the tank to the deck fitting/pump out fork, just a wye fitting. I also have a wye fitting at the merger of the pump out and direct discharge (a little upstream from the seacock). As I explained in a previous post, the only wye, of the 3 in a full option system that requires controlling is the head to tank/direct overboard junction. The other 2 will simply work by themselves as the only route open during use is the one you are actively choosing.

But I would think a small tank is just the reason to require pumping overboard. You could be looking for a pumpout station every other day otherwise.

I have a tank just for crowded anchorages and yacht club moorings where I want to be invited back. Upon leaving, I am pumping out once I clear the area.

Waiting for the 3 mile line is good but I am not going to haul poo around all day if I don't get out there. It will go out with the tide anyway...

-Britton

bcooke wrote:But I would think a small tank is just the reason to require pumping overboard. You could be looking for a pumpout station every other day otherwise.

I'd tend to agree.

Mike, what's the big deal about adding another wye?

I'm not falling for this one. I may LOOK like I just fell off the short bus, but I assure you that the fall was purely for dramatic effect.

My answer was specifically aimed at how I know Mike uses and moors his particular boat, since this is about his specific holding tank, after all.

Others' needs may vary. They always do.

The root of my opinions on holding tanks is a dissatisfaction with the laws surrounding their installation and use, but we're not getting into that here.

Tim, you are not helping here.

Mike needs more boat projects.

-Britton