Adding outlet to plastic tank

[Mark-NH]

Hi guys. I have this 800 gallon vertical tank that I haven't used yet. It would be perfect for my permeate storage. The issue is that there is no outlet at the bottom of the tank. There is a flat surface on the round tank for a fittingI. Any thoughts and input on how to get a 1 inch outlet into this Tank would be greatly appreciated. It is tall and narrow so I cannot get at any fitting from the inside.

What size drill should I use? Should I use a plastic fitting or stainless? What material is best for steeling the connection? Thanks in advance.

Mark

[wiam]

Go on eBay and search "uniseal" I have used several sizes and they work well.

[Super Sapper]

I would go with a larger fitting and reduce down outside, maybe go with 2 inch out of the tank. A 1 inch will restrict your flow and pump size if you need to go bigger in the future.

[maple flats]

I recently added a 1.5" fitting. Look up bulkhead fittings. To do it, you will need to be able to hold either the nut or the part that passes thru the hole from the inside. I chose to have the nut on the inside. Then what you have on the outside is a female pipe thread. As you tighten what you put in there it does not loosen the nut, you you have the nut on the outside, screwing anything either into or onto the part sticking out, it loosens the nut and it it difficult to hold the round part inside from reaching from a distance. When you do it the way I did, you get a choice of using the female thread or the outside thread to make your connection, it is threaded on both the inside and outside. For my 1.5" fitting I needed to use a 2 3/8" hole saw. If you get any other size, just measure the hole in the furnished gasket and that is the size hole saw you need. Just get inventive and tricky to hold the nut from a long distance, it can be done.

[lew]

What I have done in the past on poly tanks is to drill and tap it. There's usually at least 1/4 inch of material to tap. Just keep fussing with how far you run the tap in so that you leave the nipple flush with the bottom of the tank.

Another method I have used for larger holes is to install a plastic floor drain. Use a hole saw to make a 3+" hole where you want it. Place floor drain over the you just drilled on the outside of tank. Drill through floor drain flange with 1/4" bit wher appropriate. Now apply your favorite food grade gasket material to the floor drain flange, press into place and put 1/4" bolts through holes to attach flange to tank. You can reach up inside tank through your hole to tighten. I prefer stainless bolts.

With both ways, you should tilt tank towards drain for approprite drainage.. also, before you install drain in any poly tank, look inside at the bottom of the tank when it is setting upright and empty. The bottom of these tanks are usually very wavy and where you may think you want the drain may be a low spot.

[mellondome]

If you use a bulkhead fitting, you can hold the fitting from the outside. Use a piece of wite to slide the fitting down to the hole you have for it. I did this on a 250gal vertical tank that didn't have an access hole large enough to get inside.
Use a fitting larger than you need and put an elbow on the inside part , will help drain the botton of the tank

[lew]

Forgot to mention that you end up with a 3 or 4 inch drain that you cadapt down to what you need. Also, you have a complete draining of the tank. Nothing impeding flow like a bulkhead fitting would

[BreezyHill]

Go on eBay and search "uniseal" I have used several sizes and they work well.

Great share wiam...these look great. Any issues at all with them???
Thanks Ben

[wiam]

Great share wiam...these look great. Any issues at all with them???
Thanks Ben

I have used them in cage tanks with no problem even though wall is thinner than recommended. Also a rubbermade. Some home built releasers on here are made with them. MES uses them on his releasers. So easy to put together. Could elbow down inside tank to get most out. Not my favorite way to drain a poly tank....

[Dennis H.]

The only concern with the uniseals I can see is that you WILL have to anchor the pipe in some manor to keep a good solid seal.
I think that over time with a pipe that can move around will start to leak.

I use a 325 gal truck tank for hauling and it already came with a 2" Banjo bulkhead fitting. There was a 90 on the inside that is angled down to allowing emptying most of the contents. I found this worked less than optimal. The 90 was to large and once the liquid got below about 1" it would just start to suck air. I will be replacing this fitting with a smaller size fitting, 1" due to the size of my sap pump, and set it up so that it will get most of the liquid out of the tank.

Good luck. I think the toughest thing will be getting the fitting down to the hole but I like the wire method and will have to give that a try.

[OldManMaple]

This fitting goes on the bottom of tank and provides complete draining. Think you might install this through the top with some luck.

http://www.banjovalves.com/ppboltedbottomdraintankflanges.aspx

[BreezyHill]

The first thing you learn when hauling liquid is that all lines must be secured or...from a dripping leak to a total tank failure will occur at some point. I saw a tank that the banjo style fitting rubbed the plastic until the seal blew out. This was a flex pipe from a stationary pump to the storage tank. 2' of tiger flex was left on the ground. Took several years but it made a mess one hot summer day.

The angle of the cut at the end of the 90 should pickup all but 1/4" of liquid if it is cut correctly to lay nearly flat on the tank bottom. Sounds like you got one that was not for that tank. The ones in our 3000 gallon tanks all needed to be recut to drain as much as possible. Leaving a small dimple on the long cuts keeps the elbow from sucking to the tank floor. Don't block up the end or the piece will be in your strainer quickly.

[Bricklayer]

I found a company that does plastic welding. The plumber at work told me about it. He charged me 25 bucks to weld a valve to a 55 gallon poly tank. And he supplied the fitting.

[Dennis H.]

I never thought about the welded fitting option.
I know in RV's that they put some fittings on the fresh water tank by spin welding.
Spin the fitting to be joined to the tank long enough for plastic from both items to be joined to melt then stopping the spin and let them cool together.

[Bricklayer]

I'm not sure what process he used. But it hasn't leaked and it works awesome. I use my tank for raw sap so I didn't want some big black rubber o ring sitting in the tank. The fitting he welded on was food grade plastic. Same material as the tank. I also had him weld a fitting on the top of the tank that I can screw a garden hose to. To clean it out. Don't have to worry about the hose falling out when the water get to the top. Works pretty slick.

[Mark-NH]

So it turns out a slightly overweight 52 year old man can fit through a 16" diameter hole. Once I figured this out the rest was a piece of cake. I purchased a 2" bulkhead fitting from my local plumbing store, and a corresponding hole saw. This vertical tank is 10' tall so I laid it on it's side, chocked it with a couple pieces of firewood and went to work. I cut the hole 2" up from the bottom rim of the tank. This gave clearance for the bulkhead fitting and put the hole far enough above the edge so as not to weaken the tank.

The only real trick from here was setting up the fitting so it would (mostly) drain the tank. For this I screwed in an elbow to the inside of the bulkhead fitting and faced it towards the bottom of the tank. I cut a little notch in the bottom of the elbow where it almost came in contact with the floor with the idea that it would not impede flow yet it would create enough of a "seal" to mostly drain the tank.

I repeated the install of a bulkhead fitting towards the top of the tank for my inlet. As a complete surprise and bonus, the 16" round hole in the top of the tank accepted a standard screw on lid from a sap tank. I believe it will work perfectly for my needs. 800 gallons of covered, clean storage for permeate, all with a very small footprint.

Thanks to all for the input and ideas.

Mark