Determining Waste plumbing layout?

[SilverHoot]

I've read and read and haven't seen the answer to some basic questions I have regarding how to plumb my waste system. I'm in 'analysis paralysis' over how to decide where the drains from gray tank exits, where is the best area for the sewer hose hookup, is there an advantage to locating the black tank below floor instead of original above floor, how much of an angle for flow should the waste plumbing have at minimum, electric or manual waste valve, tank monitors. I've attached my crude drawing of layout. This trailer did not have a gray tank originally. The space behind the rear axle that I was thinking for the gray tank is 22.5" x 46.5" Once I get this figured out I can get back to work but at this point it's been a major mental hurdle. ANY help, opinions or sage advice is much appreciated.

Thanks,
Michael

[Arrowstream]

Well hello, I'm in the same situation. I just got a pair of 17 gallon tanks today, so now I have no excuse not to start putting things back together. If your toilet is directly above your black tank, then slope is only an issue for the tank and 3" waste pipe. My tanks have bottom slope built into them. I'm not a plumber, but the plumber that I used when building my house recommended 1/8th to 1/4th inch drop per foot. He said that with a greater drop, the flush water can sometimes outrun the flushed material. In our case (toilet discharging directly into tank) that won't be a problem. Grey water will make it's way to the tank, it's only got soap, some food particles and maybe some hair in it. Most trailers have the waste exit to the road side. I'm using manual valves located at the rear hatch. Don't forget to vent the tanks, shower, sinks (1 1/2" ABS) through the roof, and don't forget about the tank level monitors. An advantage to having the black tank above the floor is underside clearance and it should be less likely to freeze. The slope of the pipes will also be affected by how level you set your trailer up. I'll remember what else I intended to do once I get the floor and fixtures back in.

[SilverHoot]

So are your 17 gal tanks both for gray? Is your black tank located above the floor? Post some pics if you can...thanks.

[markdoane]

I think it looks like a good arrangement. The most important feature is getting the gray tank close to the shower. Since the shower outlet is at floor level, that's the one where pitch per distance can become a problem.

I used 1/4" pitch for drain lines because the pitch of the trailer is sometimes 1/8".

[Arrowstream]

One will be black, one gray, both will be below the floor and drain out the back. My trailer has the rear bath with the tub curbside and the toilet roadside. The rear 4 feet of floor is removed, so there's nothing to picture but gravel right now. There are 60 inches between the frame and 39" between the last crossmember (joist?) and the rear C channel at the back of the trailer. I bought tanks that are 32" long and 22 inches wide. They will go side by side between the frame. I am going to make an angle iron carrier for the tanks (they have a top lip) plus support them with straps to the main frame. To account for the added weight, I'm going to move the battery to the tongue and I have a new Iota converter to replace the Univolt. The new converter weighs a lot less and will be installed a few feet forward of the old Univolt's location.

[SilverHoot]

Another question that comes to mind is the best type of material the tanks should be made of, polyethylene plastic or ABS??

[loosewheel]

Hi SilverHoot, I've been considering a lay-out like your shetch. My black tank runs under the floor across the back. does your black tank extend below the floor? the reason I ask is I'm wondering if you could series the grey tank to the black tank with a remote control (cable type) gate valve in between. Then you could use the exsisting drain, empty the black tank then drain the grey tank through the black tank. Does that make any sense?

[easyride]

I`m installing 2 26 gal tanks,in myGt ,the gray tank will be in front of the axle,with the black in the rear.Toilet will sit right above black,vent to tie into original going thru roof.
Gray line will start out at the lav with a studor vent there and catching shower drain on the way to the tank, tying into curb side of tank,KSink willl tie into street side of tank venting thru roof with original vent.Drains will be under the belly pan,so that will tank a box to cover them.Dave

[SilverHoot]

loosewheel, No my black tank is actually above floor. What you say does make some sense as the gray could then rinse the black.

easyride, what is a studor vent?

[SilverHoot]

Googled studor vent, here's the site STUDOR® | IPS Corporation

[easyride]

Originally Posted by SilverHoot

loosewheel, No my black tank is actually above floor. What you say does make some sense as the gray could then rinse the black.

easyride, what is a studor vent?

As you have already googled it you know what it is . An AAV allows air to go down the line as the water drains,this keeps it from gurgling as it drains.The seal then closes to prevent fumes from coming from the tank.It cannot be used as a tank vent,as the water comes into the tank,the air in the tank must go somewhere,that`s what the vents thru the roof are for.Dave