Calculations for Holding tanks

[BJW]

Hey Guys,

I've been flip-flopping over the sizing of my holding tanks for some time and its time I get serious.  I have several thoughts and have heard a lot of ideas, but I thought that there should be someone out there that has developed or knows of a standard for calculating how much solid waste (black tank) and  waste water(grey tank) is generated per person per day.  Further, I figure someone has a calulation for how much general water is consumed/used per peson per day.   Also, is there anyone who has any idea of how much water waste is generated by just the kitchen sink?   

I thought I would give this one last try before deciding on how big to build my tanks.  I look forward to your ideas, or if you have any calculations that can be used for this purpose. 

Thanks for your help in advance.

[gumpy]

The numbers I used to calculate my tanks was 5 gallons per person per day. I wanted 7 days boondocking capability for 4 people. 5 gal x 4 people is 20 gallons per day x 7 days = 140 gallons. My tanks (fresh, combined) came out to right at 150 gallons. So far, it's been right on. It does require standard conservation (navy shower, minimal waste, dishes once a day without continuous running water).

I suggest you try to make the waste tank approximately 5-10% larger than the fresh, but not really necessary.

Personally, I could not convince myself there was any valid reason not to combine the black and grey. Didn't install a diverter, either, as I had originally planned. Haven't regretted it.

craig

[JohnEd]

BJ,

I can't say that I agree with consoladating them.  I have dumped grey water many times to lighten up prior to getting under way.  I have often needed the room after refilling my fresh tank.  I couldn't do that with black.  Seperate just gives you options and we are an "option" group.

Your bus looks just great, by the way.  I was off the board for a long time due to illness,  etc. and am behind.  Did you take much flack for having THREE slide-outs in a coach that isn't supposed to tolerate even one?

John

[Nick Badame Refrig/ACC]

BJW,

You can calculate all day long until your head is spinning!

Heres my new rule of thumb, Install the largest tanks that you can possibly fit into your compartment!!

Figure out what space you need for your piping and, Fill the rest with TANKS!

I thought that I calculated properly when I ordered tanks, turns out that I still had plenty of room fo another 100 gals.

If you follow my rule, at least you can't say that you didn't go large enough!

Good Luck
Nick Badame-

[gumpy]

BJW,

If you follow my rule, at least you can't say that you didn't go large enough!

Yeah, but you can say that you've run out of room in your bays for everything else you wanted to fit in 

It's all about proper planning and efficient use of space. My rear bay has 150 black, 150 fresh, 2x40 lb propane, valve clusters, 50' fresh water hose, 25' utility hose, 2 x fresh water filters, 2 x 2 gallon pressure tanks, 2 x water pumps, 2 x 15' dump hoses and all fittings, and a small heat exchanger/fan. I still have room to put my small utility air compressor and maybe my central vac. Oh, and there's space for a 30# can of freon which sometimes rides with me.

[Nick Badame Refrig/ACC]

And I'm sure you can still fillem all the way up!!!
Nick-

BJW,

If you follow my rule, at least you can't say that you didn't go large enough!

Yeah, but you can say that you've run out of room in your bays for everything else you wanted to fit in

It's all about proper planning and efficient use of space. My rear bay has 150 black, 150 fresh, 2x40 lb propane, valve clusters, 50' fresh water hose, 25' utility hose, 2 x fresh water filters, 2 x 2 gallon pressure tanks, 2 x water pumps, 2 x 15' dump hoses and all fittings, and a small heat exchanger/fan. I still have room to put my small utility air compressor and maybe my central vac. Oh, and there's space for a 30# can of freon which sometimes rides with me.

[gumpy]

And I'm sure you can still fillem all the way up!!!
Nick-

I didn't say I hadn't filled mine up.  Just not with only holding tanks, though they sure did take up a lot of the space. If that tunnel weren't there, I'd have been able to get a lot more in there.

OK, here's #50...

[BJW]

BJ,

I can't say that I agree with consoladating them.  I have dumped grey water many times to lighten up prior to getting under way.  I have often needed the room after refilling my fresh tank.  I couldn't do that with black.  Seperate just gives you options and we are an "option" group.

Your bus looks just great, by the way.  I was off the board for a long time due to illness,  etc. and am behind.  Did you take much flack for having THREE slide-outs in a coach that isn't supposed to tolerate even one?

John

Hi John,

I appreciate your help.  I have taken a little flak about the three slides.  I just say that everyone is right,  you can't put "a" slide in an MCI, it's got to be at least two....or three.     

The bus is great to design with.  So many people are afraid of what others think, they forget to do the math themselves.  I happen to have the resources/abilities to do the math and not worry.  I love the opinions of EVERYONE including the skeptics.  That is what helps me understand things better and what to look for, or how to stay away from major pitfalls.  I hope you have a chance to see Gus in person some day.  Are you going to be at BusNUSA at Rickreal, Or this year? 

[Dallas]

And I'm sure you can still fillem all the way up!!!
Nick-

I didn't say I hadn't filled mine up.  Just not with only holding tanks, though they sure did take up a lot of the space. If that tunnel weren't there, I'd have been able to get a lot more in there.

OK, here's #50...

Congratulations! on the big  FIVE OH!
Dallas

[TomC]

What I did was to mount a 130gal water tank under the rear bed with 2-10gal water heaters (elec) and two water pumps with my hot and cold manifold ball valve system for each water need (then can turn off just that line if it blows).  This keeps the water warm since it is inside.  Since I only have a transit, I had an 85gal gray water tank with both a left side splitter dump and a right side street dump if needed, and a 45 gal black water tank.  With my wife and I, we have dry camped for 5 days (longest without hookup I've gone) and use about 2/3rds of the fresh water.  When stopping at RV parks, I only dump the black once a week, and whenever the gray needs it.  My tank gauges are simple.  On my fresh tank, I have slits in the wood with a light above so I can see the level; the gray tank, I just go out when dark and shine a flash light into the tank; the black tank is full when the toilet "burps" when flushed-that's because my black water tank is on the centerline of the bus with the toilet on the edge with a 3" pipe that's about 3 ft long connecting it with two 90 degree turns.  And in over 12 years of use, only once did it clog when my wife used to much toilet paper and not enough water-nothing a bucket of water didn't take care of.  So, I'm living proof that the toilet does not have to be directly over the tank.  But, you'll do it your way.  Good Luck, TomC

[Ednj]

Ok guys,
Let me see if I can bore you, keep your attention and confuse you all in one post?
>
All the new high dollar coaches I see lately have only one 100-gallon fresh water tank & one combined black-gray tank.
Of coarse they only go from slab to slab, so they don't need anymore.
I have a production unit that has 40-gallon black, 60-gallon gray and 50gallon fresh. Yes I have refilled the fresh with out emptying the gray and filled the bathtub, also filled the black to the toilet.
In my conversion I have 2 tanks 65" x 23" x 12" that are fresh water and gray water, and 1 tank 44" x 24" x11" for black water.
You can do the math, c= capacity in gallons; l = length; w= width; h= height. So C=LxWxHx7.48.

Now with that said my plumbing my confuse you?
My dad had a motor home back in the day, which only had a black tank. The toilet and bathroom sink went to this tank.
The shower and kitchen sink dumped on the ground (valved).
I'm doing the plumbing right now starting on the roof and working down. It will be allot easier for me to vent both tanks if I tie in the bath sink with the black tank instead of the gray tank.
In short you have to decide how you will be using your conversion, if you are staying in campgrounds with full hook ups you don't even need tanks.
Ed-9-Nj

[Melbo]

Ednj my be right that if you stay in campgrounds you don't need tanks but I would probably install them just for laughs.

I have a 165 gal fresh water and the same in total black and grey (or should that be gray) water tanks. My thinking is if my girlfriend and I use 20 gal a day we can go a week if (we havn't taken the coach out for the test yet) if we use 30 gal a day we can go for five days and if we use 40 gal a day we can go four days. You can see the natural progression here. If she insists on long hot showers more than once a day we may need to stay in campgrounds and I could have saved the trouble of instlalling the tanks. So I guess it depends on how you will use the coach and your personal preference.

Melbo

[Danny]

I have read where a large tank might need a partition within the tank so it won't shift weight as much going around curves.  Maybe this should be a consideration.

Danny

[BJW]

The numbers I used to calculate my tanks was 5 gallons per person per day. I wanted 7 days boondocking capability for 4 people. 5 gal x 4 people is 20 gallons per day x 7 days = 140 gallons. My tanks (fresh, combined) came out to right at 150 gallons. So far, it's been right on. It does require standard conservation (navy shower, minimal waste, dishes once a day without continuous running water).

I suggest you try to make the waste tank approximately 5-10% larger than the fresh, but not really necessary.

Personally, I could not convince myself there was any valid reason not to combine the black and grey. Didn't install a diverter, either, as I had originally planned. Haven't regretted it.

craig

Hi Craig,

I know that you built your tanks. Question is-- Is that something that you would do again, verses buying custom built tanks?  I have the ability to build the tanks that I want, but have aslo considered having them built.  Did it take much time to build your tanks??   The only problem with having custom sized tanks built is the cost.......wery wery expensive!!!   Did you consider building fiberglas/wood tanks? 

Sorry for all the questions....inquiring minds you know.    Oh!  I promise, I won't be considering installing slides in the tanks.....

[gumpy]

I know that you built your tanks. Question is-- Is that something that you would do again, verses buying custom built tanks? 

Absolutely. The hard part was getting up the nerve to make the investment and try welding plastic, but building them myself allowed me to maximize utilization of my available space (i.e. I wasted very little bay space and got the most capacity I could get in my tanks).

If your bay space and/or boondocking time/capacity are critical, then consider making your own. If you are planning on using your coach only for weekends, or only travel from dump station to dump station, then you can probably use smaller, more readily available pre-made tanks.


I have the ability to build the tanks that I want, but have aslo considered having them built.  Did it take much time to build your tanks??   

I think my 4 tanks took me about a month of part time work on them. I got to a point where I could build a tank in a couple days.


Did you consider building fiberglas/wood tanks?  

No. I never could figure out how you would seal it. Seemed to me any way you made it, it was going to be impossible to completely seal it. There would always be an open seam inside. I just have to believe that anything you do to seal that seam is only going to be temporary. I suppose you could glass over the seam on the outside. That might do it, if the lid was screwed down first.  It just didn't seem to be the best solution, to me. Also, I was never able to find bulk head fittings for them. I guess they're available, I just never could find them or, at the time, get anyone to tell me where they were available. Everyone talked about them, but nobody could tell me where to find them.

I liked the glued up ABS tanks that were written about by another busnut. That seemed like a very reasonable approach, so that's the direction I initially took. When I couldn't find food grade ABS at a reasonable price, I was turned toward welded PP. Once I looked into that, it just made the most sense.


Oh!  I promise, I won't be considering installing slides in the tanks.....


Self adjusting volume! Cool idea. The tank is only the size you need it to be!