Intervention needed: DIY home-made grey tank

[Belegedhel]

I have been accused of doing things the hard way. Perhaps I am inviting an intervention...

My shell-off rebuild has been stalled for weeks now as I mull over grey tank possibilities. I have finally convinced myself that I want my tanks securely inside my frame, above the belly-pan. I checked out the 16 gallon tanks offered by Vintage Trailer Supply, and I could make them work, but they wouldn't be optimal, and they are currently out of stock for the next few weeks, which just adds to my delays. I also tried a couple of custom tank makers, but the cost is ridiculous.

I built some faux-tanks out of foam insulating sheet that I was using to help me visualize where they will fit, and what they will interfere with, and this got me thinking--why not build something from scratch?

One option would be fiberglass, which I am not too keen on as I fiberglassed my plasic wheel wells, and that was a messy smelly, job. I am also figuring that a fiberglass tank is going to be somewhat brittle, and likely to leak over time.

Another would be to buy a 3/16" or 1/8" thick sheet of polyethylene, saw it into panels, and try to plastic-weld it together into a box. I haven't heard any suggestion that welding plastic is particularly easy, so I might just be buying a 4' x 8' sheet of frustration.

Any thoughts?

[Protagonist]

You're in Houston, not too far from the Gulf Coast. If finding an RV graywater tank isn't working for you, how about a boat holding tank? West Marine has a 15-gallon tank, measuring 15×11×25 inches for $125, or a 20-gallon tank that measures 10×16×30 inches for $145. Both made of white polyethylene.

[Belegedhel]

Thanks for the suggestion, but no difficulty finding a variety of tank sizes. The constraining dimension is the depth of my frame rails, which is 5 inches. Most off-the-shelf holding tanks are 8 inches deep or more. I had checked marine tanks, and fuel tanks as well. Still that thin depth is the killer. VTS has a tank that is only 3.88" deep, which I could make work, as above, but then I need two tanks, and the overall expense of the project approaches $500. At $65 for a 4' x 8' sheet of poly, the cheap-bastard-masochist in me starts asking if I couldn't make a custom tank that would really optimize the space I have for a lot less than the cost of a commercial tank.

[Protagonist]

Ah. Misunderstood the problem. Apologies.

Found this site: Plastic-Mart - RV HOLDING TANKS

Don't know what other dimension limitations you have other than the 5" height, so I can't say they've got what you need, but it's worth a look if you haven't tried them already. They do have a couple that are only 5" tall, at least.

[195Pilot]

I have been involved in aviation for over 40 years, and rebuilt several aircraft including cabin class twins.
I can look at a project or part and tell myself I can make it better and cheaper.

I will work on a $5.00 part for 2 weeks and spend $500.00 and swear up and down I'm saving money. Some time a little knowledge and skill can be trouble.

[pbearsailor]

I made a stitch and glue epoxy based black tank for mine. It's been working just fine. Several pictures of the build buried in my thread, somewhere near the last part.

cheers,
steve

The pics of the tank start here

[65CV]

I'm not sure I'd recommend doing your first fiberglass tank in that location. Too much work to remove it if you make a mistake.

How about a custom PE tank. I kept this link from Tim at theVap: 1960 Airstream Ambassador Project! » Blog Archive » Bad news on the vintage poop!. It's for his black tank, but you could consider the same idea.

[oh2bcarefree]

We did that. And even though there was some cursing involved, my husband said we would do it again, now he knows how. No buying a tank for him. This tank does sit on top of the floor and is our black tank.

Here are a few photos, you can see more in our thread 1959 Avion... starting in post #25. No problems so far.

http://www.airforums.com/forums/f417...n-79207-2.html

Tina

[Aerowood]

I am using three 11 gal. tanks that are manifolded together. I ordered them here

RV Surplus

[DGJackson]

Check out Ameri-Kart - they make water and holding tanks in poly and ABS. They are sold by Pelland Enterprise and RV Surplus. I'm looking at a poly 27 Gallon (51 x 32 x 4.5) for a water tank and an ABS 24 Gallon (54 x 30 x 5) for a holding tank. Shipping can be a little awkward. While unit prices are little hight Pelland seems to have better shipping costs.

[Belegedhel]

Thanks all--I now have a few more suppliers that give me some new options. Might be able to talk myself out of a home made tank after all.

Of course, this didn't keep me from buyin the HF plastic welding kit (every project is an opportunity to buy new tools, as they say). Spent the better part fo Saturday figuring out how to weld polyethylene, and tried to practice by doing some repair/modification work on some rain capturing barrels that I had been working on since the airstream wasn't keeping me busy enough.

I built two small boxes out of 1/8" poly sheet (UHMW). The 1/8" might be too thin for a large tank anyway, and I am not sure whether it made it easier to weld, as there wasn't so much mass to heat up, or harder to weld as it is easy to warp it. My conclusion is that there is a reason tanks are roto-molded instead of welded panels. It isn't that easy to get a stong, consistent, water-tight weld. I'll see what the suppliers are able to do before pursuing the DIY options any further.

[jimbob79]

I added a gray tank to our 73 overlander from PPL Motor Homes (H502) that holds 25 gal plus about 5 gal in the 3" pipes that I plumed it with. The cost was about $100.00 for the tank and it fit between the rails.