Black water reconfiguring

[wal1809]

Gentlemen it is time.  I wish to start a conversation about black water tanks.  I would have thought this would have been a dead horse topic on here but searching even "Black" turned up very little.  So if this is a dead horse, I apologize in advance and carry on.

I don't mind spending money but I don't like to when I don't have to.  The bus came with what appears to be a boat black tank.  It was rigged to work and served its purpose with limited effectiveness for a while.  It had gray and black going to it and would fill up in 2 days.  So I rerouted to a separate gray.  I used a free $10 35 gallon poly tank turned on its side.  It has a valve and a garden hose for training.  It works flawlessly.  The black tank is failing.  The top is falling in and it just simply needs to be replaced. 

So if you all could post your pics, ideas ect.  Jury rigged all the way to professional jobs, I would like to see them all.  I am considering going back with one very large tank for both gray and black to save the room.  Let me know what you got especially the frugal ideas.

[wal1809]

Oh I will start off.  One thing I want is a sprinkler system in the tanks.  I installed one on my gray tank and I tell you guys that is the monkey shizzles to say the least.  When I have drained the gray tank all the way. I turn on the internal sprinkler and go do something else.  A few minutes and that water is running clear, done.

[Iceni John]

There's plenty of threads on this forum and elsewhere about poo tanks, with lots of good advice proffered.   Most people use roto-molded polyethylene tanks for all their tanks  -  they're not too expensive, reliable, available in a myriad of shapes and sizes from many suppliers around the country, and can be customized by having the inlets/outlets/vents/etc put wherever you want when the fittings are spin-welded in.   Trucking fees can be expensive for tanks, so try to find a local roto-molder where you can get them yourself.   If you can configure your poo tank to be as high as possible, it will drain with more force and be less likely to get blocked inside by the dreaded Mounds Of Doom.   A transfer pump to move excess gray water into the poo tank can be a good idea, as is having three dump valves to allow one to backflow gray water into the poo tank when dumping.   And whole chapters have been discussed about venting, so I won't repeat them here!

FYI, I have a 65-gal poo tank (about 24" high  -  see above) next to the 115-gal gray tank, with a Harbor Fright bilge pump to move gray water into the top of the poo tank if needed, and three cable-actuated valves (see above).   The loo is mounted directly above the tank for minimal water use when flushing and to prevent pipe constipation.   Each waste tank has two 2" vents  -  the poo and gray tanks' front vents are connected, the poo tank's rear vent rises (as does its methane) to a marine louvered hose vent pointing forward, and the gray tank's rear vent goes down to a venturi just above the road.   When I drive, fresh air blows into the poo tank's upper vent, through the tank, into the gray tank, and is sucked out at road level  -  no smells, simple, works well.

John

[Oonrahnjay]

..  FYI, I have a 65-gal poo tank (about 24" high  -  see above) next to the 115-gal gray tank, with a Harbor Fright bilge pump to move gray water into the top of the poo tank if needed, ....   

     I really like to keep things simple, if possible, but minimal clearance under my "transit" bus meant not a lot of room for tanks.  I balked at the idea of a grey-transfer pump, thinking it would be another thing to go wrong -- but I sure changed my mind.  My tanks about about 65 grey - 45 black (about 100 fresh - I'd have loved to have had more but see above) and the transfer pump is a godsend.  I don't think I've ever filled my black first (note: not designed to be a bus for a big family) and being able to transfer grey to the black has been very useful.
     My drain system is a "Tee" to the outlet, there is a valve into the T and a master valve to the drain pipe.  I drain my black tank first.  Since my black tank is small, I made it tall to give a good pressure-head of contents to flush it out while draining but once it's drained, I can close the master and open the drain from the grey tank, allowing a big rush of grey water into the black tank.  Then I close the grey valve (to minimize "backflow") and open the master valve to drain the "second fill" from the black tank.  If I want to repeat, I can but usually at that point, it's OK to close the black tank valve and open the grey and complete the grey drain.  Works like a charm (so far).
     BTW, I have an "Atlantis" Raritan macerator toilet and that cuts down on water into the black tank per day.

BH,  Coastal NC USA

[RJ]

My coach has two 100 gallon poly tanks, one fresh water, the other grey/black combo.  Has a fill nozzle on the top of the g/b to rinse, sounds like a sprinkler, but is more of a wiggle-wobble type of thing, and pulls from the fresh water tank.  With my short experience with this coach (last November to now), the system has worked well, drains with an appropriate "whoosh" at the dump station.  Quick rinse, another drain, and I'm good to go.

I then put five gallons of water in the g/b tank, along with one of those septic tank enzyme tabs you can pick up from HD or Lowe's.  No complaints yet, but we'll see come the Fresno summer. . .

I'm not at the coach right now, but if you'd like, I can measure the tank(s) for you.

FWIW & HTH. . .

[TomC]

I have a transit with maximum 22" of underfloor clearance. This is enough for a 45 gal black tank and a 85 gal gray tank. Both have worked flawlessly for over 20 years. The only thing I did out of the ordinary is on the gray tank, I have a right side drain to the street. I just park next to a storm drain and let 'er go. Make sure you get the heavy duty versions of your tanks. Good Luck, TomC

[Iceni John]

I have a transit with maximum 22" of underfloor clearance. This is enough for a 45 gal black tank and a 85 gal gray tank. Both have worked flawlessly for over 20 years. The only thing I did out of the ordinary is on the gray tank, I have a right side drain to the street. I just park next to a storm drain and let 'er go. Make sure you get the heavy duty versions of your tanks. Good Luck, TomC

I also have a starboard-side drain from the gray tank, with its own 1.5" cable-actuated valve that feeds an outlet directly ahead of the right rear wheels.   This outlet can also have a garden hose attached for surreptitious watering of plants etc.

Tom has a good point regarding poly tank thickness.   Get the thickest available, 3/8" at least, and just as important get the heaviest thickest-wall spin-weld fittings so they don't stretch or crack when you thread in dump valves and whatnots.

John

[Seangie]

We bought our tanks from Ronco. They are not cheap but you get what you pay for.   Its half price if you call Linda and tell her you are a professional/commercial RV builder. (She actually coaxed me into saying I was professionally building an RV)

They are solid tanks that you'll never have to replace.  They have many different designs.  http://www.ronco-plastics.net/newRonco/product_details.php?prodID=583Ours is sloped perfectly and we have a hose connection for a cleanout at the back.  I suggest adding this for any black tank.

If you don't have the budget there are many options including 100 gallon water tanks from tractor supply.

I'm sure there are many other freecycle options out there as well.

Things to think about -

Gravity
Cleanout
Connections - they will leak...  Can you access them if they do?
Tanks will bounce/move slide with bus movement. How to mount with minimal movement.
3" Drain on the drivers side - how will you hookup at the dumpsite
Emergency Overflow - where will it go if the tank overflows?
Stinkpipe/breather
SIZE/shape - ours is 40gal and with 6 of us we can get 4 maybe 5 days out of it.  7 or 8 if we just use it overnight.

Have fun.  Its a poopy job but someone's gotta do it

-Sean

[wal1809]

Seangie thank you for your reply.  I am thinking about going back to a gray and black in one 55 gallon poly drum.  It is just my wife and I.  I think we could go a week before we filled a 55 gallon.  I could also put a gray diversion hose for when we are at a place with proper disposal on site.  We could go for a long long time with diverted gray water.

My thoughts are to cut a hole in the top of the 55 gallon poly drum where the bung is located, getting the new hole cut as close to the rim as I dare, leaving just enough lip to bolt a flange to.  I will build a plywood cradle to hold the poly drum up and off of the bay floor.  The rear cradle will be one inch higher than the front.  The angle coupled with the interior spray nozzle should allow for a near perfectly complete drain of the drum.  I could store the stinky slinky under the drum contained by the cradle.

Any thoughts on attaching the flange to the drum.  I was figuring on roughing the contact surface with a grinder.  Then using that 3M marine goop they sell for boats.  I figured using the through bolts or self tappers every inch around the flange.  With self tappers I would never have to cut into the barrel to access the inside for through bolts.  I am leaning towards a good quality heavy thread self tappers.

[Iceni John]

If you're going to glue fittings into a polyethylene tank you must use adhesive specifically for polyethylene  -  other glues will not work.   I don't know if 3M 5200 will bond to polyethylene  -  I used it to attach aluminum to fiberglass, for which it makes a permanent bond after a week of curing, but poly is so "waxy" that I don't know how it would work on it.   This is one reason that roto-molders like Ronco (who made my four tanks) spin-weld their fittings to poly tanks.

Can you mount the tanks so they have open space under them, then if they leak their contents they'll drip harmlessly onto the road?   Putting a poo tank inside a bay with a floor, especially if the tank has home-made fittings, would make me very nervous!

John   

[wal1809]

The cradle I am going to build would capture contents of a leak. That is a good though you had there about the poly being so oily.  I will google and see what adhesives are out there specifically for poly.

[wal1809]

Oh wow there is a lot of products right off the bat on a google search.  The prep on the one I watched was clean with alcohol.

[Seangie]

Something to mention....I built a wooden frame to hold my black tank in place and then mounted an anchor plate on each side of my black tank and use ratchet straps to keep the tank from moving.

-Sean

[zimmysurprise]

The only thing I did out of the ordinary is on the gray tank, I have a right side drain to the street. I just park next to a storm drain and let 'er go. Make sure you get the heavy duty versions of your tanks. Good Luck, TomC

I agree with the heavy duty versions of the tanks, but the other theory might be slightly flawed.

[Oonrahnjay]

Seangie thank you for your reply.  I am thinking about going back to a gray and black in one 55 gallon poly drum.  ... 

    We all do what we need to do, but I'd think hard.  Yeah, they're cheap but a round drum in a square bay wastes a LOT of space.  Also figuring that you can probably do a better job of specifying the length of the tank to fit the depth of the bay, you might get WAY MORE capacity in what's about the same amount of bay size.  Just a thought ...