gray tank plans

[Greg1410]

I would like to add a gray tank to my 1973 Safari. I just about have my subfloor and belly pan out. I plan on keeping the black tank above the floor as in the original design. I will keep the same bathroom design. I plan on ordering the 4 inch deep tank from VTS that fits between the frame cross bars. VTS asks for drawings for drain holes etc. I would love if someone was willing to share some plans of their plumbing with this type of set up - where the inlet holes are from the kitchen sink, shower, and the outlet. Where to place waste valves, etc. Open to any and all advice.
Thanks,
Greg

[Belegedhel]

You are doing almost the exact same operation as I did in my '73 Globetrotter. I will look around and see if I still have the "technical" drawings I submitted to VTS to get my inlets and outlets spun in the right places.

In summary, I put my tanks in the two bays directly behind the bay that my single axle occupies. On the tank nearest the axles, I had two inlet/outlets spun into the top near one end. This end will be under the galley cabinetry. One hole will be the inlet for grey water from the galley, the other will be an outlet that vents to the plumbing vent stacks. The second tank has one outlet on the top side, which will also be under cabinetry, and it is just a vent.

In about the center of the rear facing side of the first tank is a hole, and in the facing side of the second tank, there is another hole that lines up with the one in the first tank. I used a short flexible fitting to tie these together so that the first tank can drain into the second tank. There is a similar hole on the rear facing side of the second tank which will be attached to the pipe that goes to the dump valve. This pipe will also have the shower drain tied into it so that the shower fills the grey tanks from the "outlet."

This complete rebuild is dragging on and on, so despite my having put these tanks in a year or two back, I really don't have any operational history to share. My one concern about my design is that the short flexible connection between the two tanks is very short and may end up putting stress on the spun on fittings as things move around. If I were to do it over, I might very well have put the first tank in the bay under the single axle, then skpped a bay, and then put the second tank where it is. I guess I'll report back in a year or so...

[Belegedhel]

15 minutes later....Well, I couldn't find the "plans" that i submitted to VTS, but attached is a picture that at least illustrates some of what I describe above (the frame is upside-down and you are looking at it from the bottom side). Note that in order to get the side inlet/outlets as low as possible, I had to cut a slot out of the bottom of two crossmembers, and then jury-rig a bolt-in link to compensate for the missing metal.

Good luck!

[Minno]

When I built our gray tanks, I opted to put the drain inlet and vent opening on the top of the tanks, close to the curb side end of the tank. The drains are on the bottom of the tanks, so they drop straight down through the belly pan. I ganged the two drains together to connect the two gray tanks together. The drains are located on the street side of the tanks. They have performed very well the last 4 or 5 years.

Chris

[dbj216]

Many folks install 4" deep waste water tanks so their Airstream has a smooth bottom. Smooth bottoms are for babies! But that is the vintage look.

I don't know what year Airstream changed their design to deeper tanks with 3" drain ports on the side. This makes draining the tanks easier. But it takes away ground clearance.

I opted for a side discharge type tank which means my tanks are 4" below the frame rail. I fabricated a tank cover to protect the tanks and keep them warm in freezing temps. This is the configuration my 86 Airstream has and I dare say the 2015 models are the same way.

I buy just a lot of stuff from VTS, and excellent supplier of parts. However, I elected to purchase my tanks from Inca Plastics in California. Inca has a huge on line catalog. I just thumbed through it until I found a tank configuration that fit the frame bays I elected to hang the tanks. My tanks are 25 gallon capacity.

Further, Inca Plastics has a sealing grommet that offers more flexibility for changes than the spin welds. I used the grommets and have had no problems with them over the last two years. I could determine where I wanted the drain to penetrate the floor, drill a hole in the floor, mount the tank, and use the floor as a drill bushing for my 2 1/8 hole saw. Then the tank came down, and I pressed in the grommets. It worked for me. No pipe threads and no adhesive.

Designing your drain plumbing requires a lot of considerations. You must consider wheel wells, cabinets, traps, roof vents and the like.

Hope this offers an alternative to waste water tanks in a vintage Airstream. I chose functionality over form for my trailer. And so far it works fine. I can hook up my sewer hose and drain the tanks like normal people, even though my trailer has an appendage on its belly.

David

[Greg1410]

thanks for the advice all. I think I will draw my plans up and post them here.
Greg

[dbj216]

Don't laugh, but I made several sketches of plans for my bathroom. I tried to draw things to scale. The rear bath in my Trade Wind is "spherical" due to the end caps. And then there is this big old window to contend with. I now have second thoughts about the shower. It takes up a lot of room for just a bare minimum space to spray off. All the campgrounds I have visited have a bath house which is good enough for me. And I wanted a below floor black tank moved forward, not in the rear most frame bay. So the toilet had to be between the frame rails and in the forward part of the bath. I had two roof vents in the bathroom, and one vent for the galley sink. Three roof vents with three potentials for roof leaks. But I utilized all three.

Here is my final sketch that I used as a master plan. The only change I made was deciding to drain the bathroom sink into my black tank to better utilize waste water capacity, and keep my black tank "wet" which helps it rinse clean. However, a lot of folks caution against this because if my sink trap drys out and opens up, I will get sewer smell in the trailer.

David

[Minno]

We went with the sink drain into the black tank option, for the same reasons as you. We have had no difficulties with sewer gas back into the trailer. We also have had no issues with black tank getting clogged (as we had before we moved the sink drain). We rinse our black tank very well after use and before storage.
Chris linked our grey and black tank vents together so we only have 1 vent stack out the roof of the trailer. We have had no problems with that either.

Kay

[dbj216]

I hope greg1410 reads your ongoing Little Girl rehab thread. Search threads started by Minno. You and Chris did excellent work building out your Airstream, a Sovereign if I recall correctly. Your bath is much better than mine, especially the way you made the curved cabinets. You may have had more floor space than my little Trade Wind offered. Chris built some awesome cabinets, much better than what it had when you started. And he welded up his own ABS sheet black tank instead of buying one.

David

PS We moved from beautiful Minnesota to majestic Colorado to be closer to our sons.

[Chuck]

Originally Posted by Minno

We went with the sink drain into the black tank option, for the same reasons as you. We have had no difficulties with sewer gas back into the trailer.

fwiw, if the trap dries out, you'd have the same problem no matter which tank you drain it into.

But anyway, now I'm thinking of draining the bathroom sink into the black tank, too. The drain will pass right by the black tank vent, anyway..it would be just as easy to plumb it into that. In my situation, I will have probably "extra" black tank capacity...there's no such thing as enough grey water capacity. And since there probably isn't very much volume coming from the bathroom sink, its not likely that you'd use up all the black tank capacity because of it...more likely to help things, as you've mentioned.

I was looking at an "rv doctor" video the other day on youtube, and it was mentioned that its common for bathroom sinks to plumb into the black tank. Decisions, decisions...

[Minno]

Originally Posted by dbj216

I hope greg1410 reads your ongoing Little Girl rehab thread. Search threads started by Minno. You and Chris did excellent work building out your Airstream, a Sovereign if I recall correctly. Your bath is much better than mine, especially the way you made the curved cabinets. You may have had more floor space than my little Trade Wind offered. Chris built some awesome cabinets, much better than what it had when you started. And he welded up his own ABS sheet black tank instead of buying one.

David

PS We moved from beautiful Minnesota to majestic Colorado to be closer to our sons.

Thank you David! I wondered why you showed up as Colorado all of a sudden instead of MN....
Yes, Chris built our tanks because we couldn't get the configuration and size we wanted without spending mucho bucks on it. He says "necessity is the mother of invention".
The company Chris works for now is just outside of Denver, so I'm sure we'll be out there one of the days. Maybe we can get together!

Kay

[dbj216]

It would be a pleasure to meet you and/or Chris. Be sure to PM me if you get Denver plans. Denver appears to be a significant RV destination city. I see many trailers in RV storage lots as I drive I-76 and I-70.

David

[PA BAMBI II]

Originally Posted by Belegedhel

There is a similar hole on the rear facing side of the second tank which will be attached to the pipe that goes to the dump valve. This pipe will also have the shower drain tied into it so that the shower fills the grey tanks from the "outlet."

Greetings- can you tell me if it is OK/possible to have the sink as well fill the tank from the "outlet" as well as the shower line? I am looking into having my tank fabricated soon and hoping to simplify things by having the sink and shower connected to the same inlet which is also the outlet. Both would fill the tank from the same fitting which would also serve as the drain.

Would there be any issue with this idea?

Thanks for your consideration!

[Belegedhel]

That is basically the way I have mine plumbed. I have my kitchen sink drain into the top of one of the tanks, but the shower and bathroom sink drain plumbing meet up under the floor and tie into the drain pipe going from the aft-most grey tank to the dump valve.

good luck!

[PA BAMBI II]

Originally Posted by Belegedhel

That is basically the way I have mine plumbed. I have my kitchen sink drain into the top of one of the tanks, but the shower and bathroom sink drain plumbing meet up under the floor and tie into the drain pipe going from the aft-most grey tank to the dump valve.

good luck!

Good to hear. I will only have one sink (trailer is only 17' long; two sinks seems a bit overkill). I have lots of things in the way (freshwater tank/wheel well/etc.), preventing me from draining the sink into the top of the tank, so my plan is to run the drain for the sink around the obstacles and down under the floor, then tie it into the shower drain line and the tank in just one spot.

Seems from your experience that it should work. The only thing I am concerned about is that the "inlet/outlet" fitting will be fairly low on the tank and will that cause a problem with fill capacity?

We don't boondock much...this will be more of a luxury than anything. Thanks!

[Belegedhel]

As long as what you are draining is higher than the top surface of the water in the grey tank, then you should have no problem filling the tank all the way up to the top.

The issue is that since it is impossible with the spun-on fittings to get your drain fitting absolutely flush with the bottom surface of the tank, unless you work at it, you will always leave a little water behind in the tank. Some raising of the tongue jack should take care of this issue, though.

good luck!

[TG Twinkie]

Where is the vent for the tank?

[PA BAMBI II]

Originally Posted by TG Twinkie

Where is the vent for the tank?

That will be on the top of the tank, curbside. I will run the vent line up under our custom bunkbeds and up the existing refrigerator chimney through flexible PVC pipe/hose.