Post by: Gary Hatt - Publisher BCM

If you were to convert another bus from scratch and you had a flush toilet, would you install separate Black and Gray Tanks or a combination of Black/Gray tank?

I have had both, separate and combined grey/black water tanks.  My current 1967 Eagle has two separate tanks for gray and black.  My MC-7 Combo had a 250-gallon fresh water tank and a combination 250-gallon gray/black tank.  I liked that setup and would probably go with that again, with an option of draining the gray water off before it runs into the tank if I was boondocking in a place that allows that. 

I also like having large capacity tanks as you generally pay a fixed price to dump your tanks no matter the size, when you do have to pay.  Having larger tanks also means less frequent trips to the dump station meaning more miles between dump stations.  You do, however, have to be cognizant of the weight of the liquids in oversized tanks.  Water weighs approximately 8 lbs. per gallon, and the weight is constant as you drain the fresh water, the gray and/or black water tanks fill up unless, of course, you are in a location where you can drain the gray water off onto the ground (with a long hose away from the bus of course)

As an alternative, you can always go with a Compost Toilet such as Nature’s Head.  Then all you have to do is dig a hole in the ground and bury your waste or dump it in an approved waste system along the highway.

Or you can go with an Electric Toilet.  We had an outhouse with an electric toilet in the cabin we had on the lake growing up.  But that requires some serious electricity to burn up the waste.

What are your thoughts?

Post by: Dave5Cs

We rarely use our fresh water tank unless we’re boondocking.  All three of our tanks only hold 45 gallons. I don’t know why the original builder went so small, but our guess is they stayed in campsites while at the races.  The previous owner was part of a race team.  If I did it again it would be 100 gallon freshwater, 80 gray, and 50 black. Right now, we get three showers and dishwashing out of the gray.  The black tank is good for six days.  I can't leave the bay door open to leave the hose hooked up.  A cat got in the bay for three days.  After that, I had to pull out stuff and steam clean it. Now I dump every two days on the gray. It's too low to drain out of the bottom of the bus.

Post by: luvrbus

Our MCI-5 and the MC-8 had a combo tank.  I never did like the combo tank setup.  All our other buses and RVs have always had separate tanks.  Even Sonja's camper van has gray and black tanks.

Post by: silversport

I would do my build the same as I have now, 140 gallons fresh, 90 gallons gray, 90 gallons black. Plumbed in with the gray tank is an overflow to the black tank.  In 12 years, it was used maybe 10 times.  To dump the gray tank, the fluid goes out though the black tank to exit the system.  I have pulled my tanks (for other repairs/addons) and have found the gray tank is always dirtier than the black tank. Dumping gray water on the ground is becoming less of an option.

I never have liked the compost toilets.  The main reason is that the liquid and solid must be separated, and when Montezuma's Revenge hits you, this setup can have problems. With our tank configuration, we have boondocked for three weeks without running out of fresh water and waste storage.

Post by: dtcerrato

Our setup for tanks is 75 gallons gray, 75 gallons black, and 100 gallons potable.  We also have two 7-1/2-gallon portable potables.  The gray and black tanks are plumbed with 3'' drains that can be either or both combined. It has served us well for 4-1/2 decades.

Editors Note:  Using 3” drain valves for both the grey and black tanks makes dumping significantly faster which is helpful if you are in a busy place with a line of rigs behind you.  It also flushes out your tanks faster, potentially leaving less buildup in your tanks.

Post by: Van

I just recently reconfigured the water bay with larger tanks.  The setup is a freshwater tank and combined gray/black tanks.  This provides more room with less stress.  The last setup was ridiculously small.  42 gallons for the full-timing.  That was not sufficient for our purposes for two people, nor for the 40’ coach that we have.

Post by: rusty

I prefer separate gray and black tanks.  I dump the black tank, then send gray water through the black tank to help flush it.  This works well in both Eagles.

Post by: Jim Blackwood

I went with separate tanks.  I never much liked the idea of a combined tank, just because the gray tank tends to be the limiting factor.  I'm aware, some places out west you can't dump gray on the ground.  But I'll mostly stay in the east where usually you can.  I'm not fitting a Sinkerator so that means probably the worst thing in the gray will be laundry detergent. I don't expect that to be much of a problem, and as much as it rains in the east, I doubt they will ever change the regulations.  Or at least not while it affects me. But regardless, it means I can offload the bulk of the wastewater without having to find a sanitary dump location and the black tank is large enough to go a long time. Should I ever find that I have to full-time in the bus, that might be a consideration. 

I can remember times when larger tanks certainly would have been helpful. Circumstances can turn on a dime sometimes. My bus is my safety net. Should catastrophe befall us it still represents acceptably comfortable living quarters. Having made do in my life with a great deal less, I feel very fortunate to have that. I have experienced the Homeless life and once you have done that you will never see things quite the same again.

By comparison, the bus is a tremendous luxury. But to do it right it needs certain things. An unobtrusive means of disposing of waste materials is at the top of the list and the more you can take advantage of opportunities that already exist, the better. Now of course if you do have the luxury of doing things in the best possible way as most of us do there is little reason not to. But the last thing I'd want is to find myself with a full tank, and no way to dump them.