Teardrops n Tiny Travel Trailers

So what is so special about waste storage tanks? They are just plastic containers with a few do-dads on them. So how about using another container modified to be a waste tank. Frankly I do not have a few hundred bucks to drop on storage tanks. First to start how about a grey water tank made from a 5 gal. gasoline container? I have a couple extra ones in the garage.

For the amount of time you will be using them yes you can get away with other than purpose made. The reason for using a purpose made tank is what goes into them. One of the tests for sewer pipe is a sample immersed in a concentrated soap solution, amazing what will destroy plastics.
The big advantage of a purpose built tank is ease of plumbing and disposal of waste.
I am seeing purpose built gray water tanks for $60 on ebay.

If it is possible to use a 5 gal fuel container as a black water storage tank, then what would one have to do to make it work? Obviously one would need to make a connection point for main sewer connection. On a black water tank I am guessing no venting would be needed on the tank because venting is through a stack in the trailer plumbing. Am I correct in this? How about emptying a tank? There would need to be a fitting for a garden hose right?

Hi Guy:

Yes you could use a plastic gasoline can. No you would not need to vent the tank as long as there is a vent somewhere in your system. You would not need a garden hose fitting. What would you use that for? flushing out the tank? The problem I see would be you would need a 3" flange fitting to hook to your toilet for the incoming waste and one in the bottom to go to your dump valve and hose, and all this for just 5 gals? Or are you just talking about a grey water tank?

I purchased a 16 gal water tank on evilbay, (these tanks start at about $20 and go up in cost compared to the size) (as you found, black water tanks are much more expensive, but are built to a taper so the solids drain out better) and added the 3" flanges and it works fine. I just flush the tank thru the toilet when dumping.

Hope that helps.

I found 40 of these !

The guy wanted $5.00 each.

I bought 6 for me and 2 for a buddy. They had contained car wash soap.



They have a 3/4" and a 2" NPT threaded bung just like their 55 gallon cousins.

I figured 1 for pottable water, 1 for rainwater harvest ,and one for greywater storage.

Draw from the 2" with a tee installed for a cleanout drain and utilize the 3/4" for the vent stacks

pappaw wrote:Hi Guy:

Yes you could use a plastic gasoline can. No you would not need to vent the tank as long as there is a vent somewhere in your system. You would not need a garden hose fitting. What would you use that for? flushing out the tank? The problem I see would be you would need a 3" flange fitting to hook to your toilet for the incoming waste and one in the bottom to go to your dump valve and hose, and all this for just 5 gals? Or are you just talking about a grey water tank?

I purchased a 16 gal water tank on evilbay, (these tanks start at about $20 and go up in cost compared to the size) (as you found, black water tanks are much more expensive, but are built to a taper so the solids drain out better) and added the 3" flanges and it works fine. I just flush the tank thru the toilet when dumping.

Hope that helps.

Yes 5 gal is too small. I think a 12 gal would be good for me. It is for black water and it is meant to be portable. If there is a 3" for incoming sewage could this not simply be used to empty it at the dump station? I would be bringing the tank seperate to the dump station for clean out so the toilet would not be used for flushing it out obviously. I thought I would try out the 5 gal container and if it was not working, then I could invest in a bigger better tank.

bobhenry wrote:I found 40 of these !

The guy wanted $5.00 each.

I bought 6 for me and 2 for a buddy. They had contained car wash soap.



They have a 3/4" and a 2" NPT threaded bung just like their 55 gallon cousins.

I figured 1 for pottable water, 1 for rainwater harvest ,and one for greywater storage.

Draw from the 2" with a tee installed for a cleanout drain and utilize the 3/4" for the vent stacks

How big are those and where did you get them? Was it from a local car wash?


By the way, I just knew you would respond to this post. If you want to catch fish you have to use the right bait!

15 gallon ! if you are asking volumn

and if you are wanting dimensions if I have to guess about 16" in diameter and 32 - 36 inches tall.

I imagine ANY car wash will have something similar.

bobhenry wrote:15 gallon ! if you are asking volumn

and if you are wanting dimensions if I have to guess about 16" in diameter and 32 - 36 inches tall.

I imagine ANY car wash will have something similar.

15 gal is plenty big enough and if they were near 16" in dia they would be small enough to fit under the trailer as well. I think I will go to a local car wash! Thanks for the idea.

THis is what I did to make a grey water tank for my trailer. Took some 3" black pvc joined them together and had the drain of the sink head in. i didnt do a p-trap which i am sure i will regret later. i started out with one drain and then i realized if i needed to get something out i should have caps on all of them, so i added those. I am happy with them, they should hold about 4 gallons.

Forrest747 wrote:THis is what I did to make a grey water tank for my trailer. Took some 3" black pvc joined them together and had the drain of the sink head in. i didnt do a p-trap which i am sure i will regret later. i started out with one drain and then i realized if i needed to get something out i should have caps on all of them, so i added those. I am happy with them, they should hold about 4 gallons.

I will have a shower and a sink so the grey water will need to be more substantial than 4 gallons. The good thing about it is that it can be easily made to have whatever fittings you want on it. It makes me wonder about using the really big size PVC tube. I wonder how much a 4' length of pipe with 4" diameter would hold? Can you tell I am a fine arts major?

That would be 306 cubic inches or about 2.6 gallons. About 22 lbs given 8.34 lbs of water per gallon That is 4 inch diameter and 48 in length

If I had been brave and went with 4 inch instead of 3 I would have a capacity or 7.7 gallons instaed of the 4.3 I have

Once you add the large fitting to make one of these tanks I do not think it is such an economical solution. Still I am trying to work out how I could add a 3" sewer inlet to a 5 gal plastic fuel container.


Any ideas on how one might go about doing that? I cannot think of any way to do it.

I am still trying to figure out what fitting. I really an clueless when it comes to RV waste fittings. Looking forward to ur build

Forrest747 wrote:I am still trying to figure out what fitting. I really an clueless when it comes to RV waste fittings. Looking forward to ur build

I have to be more clueless on the subject than you. I understand house bathroom plumbing but this is a whole nother ball game. I am thinking that if there is a good solution to adding a 3" inlet to a 5 gall fuel tank then there are some advantages to it in my situation. For one I can carry a full 5 gal fuel container. Infact I can carry one in each hand. They have a nice centered handle on them. If I had two I could load on up and switch to the other.


My build is almost complete. I am getting down to these plumbing issues.