Running Dual Black Tanks.....

[Colonel_Monk]

Howdy

I'm designing a compact travel trailer which is focused on extended dry camping and crossing the USA.

I'm liking the layout that I have but due to small size I've got the combo shower/toilet in the front of the trailer. This is fine except for I don't want the 42 gallon black tank in the front of the trailer. For weight balance I need to move it aft.

Though I have been thinking about a composting toilet, sounds to me like they can be a real hassle, especially if west of the rockies.

So I'm coming up with a plan to make this work, bear with me....

I'm thinking of placing a small black tank directly under the RV toilet. Probably something in the "several gallons" range. (they do exist)

Plumb that black tank to a permanent marine-style macerator pump.

Plumb the output of the macerator pump to my main black tank located near the axles.

When small tank is full, flip the macerator switch and pump it out into the main black tank.

Main black tank will drain just as all normal black tanks do.

I'd probably also put a 3" drain drop on the mini tank just in case there are problems it can still be emptied and flushed for "service".

Anybody done something like this? Comments?

Thanks

CM

[Colonel_Monk]

MudChucker wrote:
Honestly, I don't know. I never had a stink issue, always had Room for more between dumps and like I said, never had to. Flush the 2 inch line.

Hah, I didn't really think about the fact it would be rather difficult to know what was in what tank..... And we don't really want to know!

Thanks

[bikendan]

Fulltimer50 wrote:
Most have a problem of the gray water tank filling when dry camping.

x2! you should be worrying about a bigger GRAY tank, not a bigger black tank.

[MudChucker]

Honestly, I don't know. I never had a stink issue, always had Room for more between dumps and like I said, never had to. Flush the 2 inch line.

[Colonel_Monk]

MudChucker wrote:
I added a second grey tank to my elk ridge by reducing the 3 inch outlet to 2 inch and running a pipe along the bottom of the trailer up to the oem tank. I tee'd it in just before the dump valve... Idea being it would equalize between both tanks. I installed a couple Y along the way and had threaded caps on them, I made a single thread on with garden hose attachment to flush the pipe if I ever had to.. I never had to.

I bought one of those twist on blades as well and by closing that blade I could pull my black and one grey and let the liquid equalize... When I dumped them both I still had the galley tank and second grey tank to dump and rinse with.

Those are some good ideas. Water pressure to blow any clogs....

With the 2" reduction, do you find that you end up with liquid flowing to the down stream tank, and more chunks in the tank under the toilet?

CM

[MudChucker]

I added a second grey tank to my elk ridge by reducing the 3 inch outlet to 2 inch and running a pipe along the bottom of the trailer up to the oem tank. I tee'd it in just before the dump valve... Idea being it would equalize between both tanks. I installed a couple Y along the way and had threaded caps on them, I made a single thread on with garden hose attachment to flush the pipe if I ever had to.. I never had to.

I bought one of those twist on blades as well and by closing that blade I could pull my black and one grey and let the liquid equalize... When I dumped them both I still had the galley tank and second grey tank to dump and rinse with.

[Colonel_Monk]

MudChucker wrote:
Is there any reason why you just can't run a 3 inch abs pipe from front to a tank in the back back? Install a cleanout so you can flush the pipe as required...

What is the clearance between the bottom of the floor and the top of the axel?

Howdy

The clearance I haven't worked out yet. I have been looking at only slimline tanks though trying to keep the clearance as high as possible, and also plan to put whatever shallow under storage I can get for long shore power cords and hoses for macerator dumping. That was a hassle in my old rig, and I don't want to have to deal with that stuff again. Concrete mixing tray makes a good holder for a long hose....

Now, do you mean run ABS from the toilet to the tank, or between the tanks?

I had not thought of that. But that's a potential great point. Assuming the 3" drain on small tank higher than big black tank, I may be able to just pull the valve and have it flow that direction.

I had toyed with the idea of an electric tongue jack and if I jacked the front way up and pulled the valve it may well just flow in there.....

I have not gotten that far with layout, I have picked some components and reserved space for things, I'm on the 3rd floorplan now.

Thanks for all the suggestions, as with any problem that needs to be solved there are many ways to approach it. It doesn't mean they won't work or aren't right, but after you look at them all for their merits you're ready to make a WAG (w!ld a** guess) as to which is the best idea.

CM

[Colonel_Monk]

Joe417 wrote:
Another thing, I remember someone on RV.net adding a homemade tank to their TC made from 6 inch PVC drain pipe T'd together. Gave them a lot more storage but I don't remember the specifics.

Yes, I have seen such a thing but the one I saw was on a van conversion... But sure that is not a bad idea at all.

[Colonel_Monk]

Joe417 wrote:
You may want to look at TC tanks. There are many that are odd shaped to fit a specific design.

The tank in my TC is L shaped with the short side being the deep end. It's about 16 inches wide and maybe 6 feet on the long length.

It runs down the right side of the TC with the input and output being at the back left, putting the majority of the weight at the backend of the camper.

Being conservative, the wife and I have gone 7 days without dumping. Might could have made it more but wanted the weight off the truck.

Yeah! I'll do that. If majority weight is rearward and I can still p**p into the tank, that might work!

[MudChucker]

Is there any reason why you just can't run a 3 inch abs pipe from front to a tank in the back back? Install a cleanout so you can flush the pipe as required...

What is the clearance between the bottom of the floor and the top of the axel?

[Joe417]

Another thing, I remember someone on RV.net adding a homemade tank to their TC made from 6 inch PVC drain pipe T'd together. Gave them a lot more storage but I don't remember the specifics.

[Joe417]

You may want to look at TC tanks. There are many that are odd shaped to fit a specific design.

The tank in my TC is L shaped with the short side being the deep end. It's about 16 inches wide and maybe 6 feet on the long length.

It runs down the right side of the TC with the input and output being at the back left, putting the majority of the weight at the backend of the camper.

Being conservative, the wife and I have gone 7 days without dumping. Might could have made it more but wanted the weight off the truck.

[Colonel_Monk]

Lynnmor wrote:
You would need a valve between the two tanks unless the pump can be relied on to act as a valve. The problem is the waste will overfill the lower tank when parked or traveling on an incline.

Great point. I don't know the answer to that, thanks for the idea.

Maybe the discharge from macerator needs to come into top of big black tank so that it couldn't backfeed unless full to the top....

Hmmmm...

[Colonel_Monk]

Fulltimer50 wrote:
Most have a problem of the gray water tank filling when dry camping.

Agreed. I have cheated and backfilled my gray into black tank before. Can't promise that would work for everyone though! :E Tanks need to be at the same height and you need to be sure which one is most full...

One of the events I do is 2-3 weeks and with a supplied outside shower, the black ends up being the most full. Doing regular camping it's easy to fill the gray first with bathing and dishwashing.

[Lynnmor]

You would need a valve between the two tanks unless the pump can be relied on to act as a valve. The problem is the waste will overfill the lower tank when parked or traveling on an incline.