# Question on drilling holes in propane tank ..



## patch53 (Feb 26, 2010)

Gents, when you drill your holes in propane tanks for the fittings, how do line them up to keep them horizontal on the sides of the propane tank?  If I drill a hole with a hole saw it has to be flush with the tank, but the side of the tank is curved. Do I have to shave off some metal after the hole is made to get the fitting to fit horizontally in the tank?


thx, Pat


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## taxidermist (Feb 26, 2010)

Pat all my holes are in the top of both of my tanks. What are you putting holes in the side for?

Rob


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## patch53 (Feb 26, 2010)

taxidermist said:
			
		

> Pat all my holes are in the top of both of my tanks. What are you putting holes in the side for?
> 
> Rob



LOL , well I haven't drilled any yet, I was wondering if I was about to do something wrong.  Does everyone use dip tubes for the plumbing?

Pat


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## taxidermist (Feb 26, 2010)

patch53 said:
			
		

> taxidermist said:
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Most of the tanks have a hole in the bottom for return. If they dont you can use a top port with a tube for your return. You can see some tank pics in my blog. What ever you do dont try to weld a cast coupling to the tank like I did. weld a weldolet or a peice of black pipe then screw coupling to that.

Rob


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## ewdudley (Feb 26, 2010)

taxidermist said:
			
		

> Most of the tanks have a hole in the bottom for return. If they dont you can use a top port with a tube for your return. You can see some tank pics in my blog. What ever you do dont try to weld a cast coupling to the tank like I did. weld a weldolet or a peice of black pipe then screw coupling to that.
> 
> Rob



Now I feel a little less foolish for not recognizing that I had cast iron when it wouldn't weld.  I found out what you might want is a '3000 psi' forged steel half-coupling, which even I could weld.

As far as welding with the curved surface, I just heated the lip of the hole and persuaded it to become flat enough to weld with a not-so-big hammer.


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## stee6043 (Feb 26, 2010)

My tanks did not have bottom drains.  I installed dip tubes using 1" copper inside the tanks....


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## patch53 (Feb 26, 2010)

ewdudley said:
			
		

> taxidermist said:
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I have forged shedule 80 3000 lb couplings.  I am using all 1 1/2" couplings for my connections. I have a 1 1/2" outlet on the tank on the bottom I can use for my return back to my boiler. How do I plumb in the supply fitting from the boiler? If I put it on the top of the tank its going to send the hot water into the tank going straight down and mix the tank.  I thought the supply fittings were supposed to go into the tank horizontally to create stratification?  So the fittng would have to be put on the side of the tank about 3-4" from the top, but the tank has a major curve to it at that point?  What am I missing here?

Pat


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## timberr (Feb 26, 2010)

Patch,

I used a hole saw to drill 3 holes in my tank and had (3)  1 1/2" weldolets welded in place. On one end at about half way down I put one hole (Supply from Boiler). On the other end about 3/4" down I drilled 2 holes, these are for the return to the boiler and return from my primary loop.

There is a hole on the bottom which I have plumber for my drain.

Good luck


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## ewdudley (Feb 26, 2010)

> How do I plumb in the supply fitting from the boiler? If I put it on the top of the tank its going to send the hot water into the tank going straight down and mix the tank.  I thought the supply fittings were supposed to go into the tank horizontally to create stratification?  So the fittng would have to be put on the side of the tank about 3-4" from the top, but the tank has a major curve to it at that point?  What am I missing here?



Ideally sneaking an elbow with a couple of inches of sideways pipe would probably be best.  Failing that, here's what I came up with:

https://www.hearth.com/econtent/index.php/forums/viewthread/49119/


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## patch53 (Feb 26, 2010)

timberr said:
			
		

> Patch,
> 
> I used a hole saw to drill 3 holes in my tank and had (3)  1 1/2" weldolets welded in place. On one end at about half way down I put one hole (Supply from Boiler). On the other end about 3/4" down I drilled 2 holes, these are for the return to the boiler and return from my primary loop.
> 
> ...



If you cut a hole in the side of a propane tank, it will be on a curved surface. Any pipe connected to it will be pointing into the tank at angle that will be going somewhat up or down. If you cut the hole at the midpoint of the tank it will send water into the middle portion of the tank. I aways thought you wanted the supply water to enter the tank so it tended to stay at the top, and return water from the house zones to enter the tank so it stayed near the bottom so as not to mess up the startification. It seems to me the only way to do that is to cut the holes on the ends of the tank and run the piping in horizontally, but the hole angle will mean the couplings will be pointing mainly up or down, not horizontally. How is that overcome?

Pat


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## ewdudley (Feb 26, 2010)

[quote ]
Good luck[/quote]
It seems to me the only way to do that is to cut the holes on the ends of the tank and run the piping in horizontally, but the hole angle will mean the couplings will be pointing mainly up or down, not horizontally. How is that overcome?

[/quote]

Pat, 

Coming in the top of one end would be ideal, just cut the hole and then file it out until it will accept a piece of pipe parallel to the wall of the tank and weld it in place.  Ideally you would extend the pipe the length of the tank and then cut a slot in the side for best diffusion.  If you did that you would probably need to devise some way of supporting the far end, or bring it right on out the opposite end and cap it off.

--ewd


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## DaveBP (Feb 26, 2010)

You can weld black steel pipe right into the tank if you want. Using a length of larger pipe will slow down the water as it goes into the tank and help minimize mixing. Then outside the tank you can bush it down to the supply pipe size. 2 inch X 18" nipples are good candidates.
You can end up with some kind of oval hole to get the water to enter the tank at the preferred angle. This is not a job for a hole saw but an oxy-acetylene cutting torch is way faster than a hole saw anyway.

 Here's one method:

PVC drain pipe is about the same OD as steel pipe of the same size. You can take a piece of PVC pipe and cut it to fit the curve of the tank where you want to go in and at the angle you want. This doesn't need to be an airtight fit but approximate. Band saw, belt sand, hacksaw, grinding wheel (be prepared to redress the wheel afterward) whatever you have to shape it to the surface of the tank. Then sand/grind off the tank's paint out to a couple inches away from where you will be welding. Hold the PVC pipe where you want it and mark around its outline with soapstone marker. Get out your cutting torch and cut it out inside that outline and pointing the flame  parallel to the pipe's intended direction into the tank. Then with your actual piece of pipe start filing or grinding away the cutting slag and whatever steel is left until you get the pipe to fit as well as you can inside the hole in the tank. A cylindrical carbide bur in a pistol drill works pretty well. A high RPM die grinder is best but if you have one of those you probably don't need my advice on doing this.

Bear in mind that if you get out to a long oval to get the pipe farther away from perpendicular to the tank surface it will give you a sharp inside corner between the pipe and tank at one end of the oval that can be tricky to weld into. Check with your welder to see how comfortable they are with what you want to do before cutting a big hole in the tank. The closer the pipe fits into the hole in the tank, the easier it will be to make a leak free weld.

Bon appetit.


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## ewdudley (Feb 26, 2010)

DaveBP said:
			
		

> This is not a job for a hole saw but an oxy-acetylene cutting torch is way faster than a hole saw anyway.



You might be surprised, Dave, I know I sure was.  

Properly lubricated, those Lennox hole saws will walk an inch and a half hole right through 5/16' steel much faster than I would ever have expected, on the order of two minutes or less.  If you don't need a neat job the torch might be faster, but by the time you clean up a torched hole to be as precise as the drilled hole, the drilled hole is a faster and nicer.

--ewd


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## timberr (Feb 26, 2010)

I used a hole saw to cut my 3 holes and it was very fast (< 5 min. for all 3). As for the comment about the direction the holes are pointing. The supply on mine is dead center of the end so that water goes in straight. The to returns are in the lower end and do point up. When I am running on storage I usually see 208 to 25* of stratification. Since the water is moving at 1-2 gal/min I don't think the angle has much effect on stratification. I have noticed that the water volocity is more important.


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## patch53 (Feb 26, 2010)

ewdudley said:
			
		

> [quote ]
> Good luck


It seems to me the only way to do that is to cut the holes on the ends of the tank and run the piping in horizontally, but the hole angle will mean the couplings will be pointing mainly up or down, not horizontally. How is that overcome?

[/quote]

Pat, 

Coming in the top of one end would be ideal, just cut the hole and then file it out until it will accept a piece of pipe parallel to the wall of the tank and weld it in place.  Ideally you would extend the pipe the length of the tank and then cut a slot in the side for best diffusion.  If you did that you would probably need to devise some way of supporting the far end, or bring it right on out the opposite end and cap it off.

--ewd[/quote]

Elliot, this is what I was thinking of doing. My buddy gave me a carbide bit hole saw to use so it shouldn't be too bad. he also has a big dremel-like tool that I can use to grind away some metal at the top and bottom of the hole so the coupling will fit in horizontally. I think I'm actually going to use a 2" double threaded coupling for the boiler supply line and run a diffuser pipe inside. I should be able to slow the flow down a lot with a short length of 2" pipe about 2 feet long before entering the tank, and then have it diffuse upward once in the tank. I'll only run about 3 feet into the tank though.

thx, Pat


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## bulldogbones (Feb 26, 2010)

Ok I give up what are you using the tank for?


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## DaveBP (Feb 26, 2010)

> You might be surprised, Dave, I know I sure was.
> 
> Properly lubricated, those Lennox hole saws will walk an inch and a half hole right through 5/16’ steel much faster than I would ever have expected, on the order of two minutes or less.  If you don’t need a neat job the torch might be faster, but by the time you clean up a torched hole to be as precise as the drilled hole, the drilled hole is a faster and nicer.



I would like to watch that hole saw cut a hole at a 30 degree angle to the surface in a hand held power tool. Actually, watching the guy trying to hold on to that power drill sounds like a YouToob moment. 

A circular hole perpendicular to the surface is for hole saws. I'll grant you that. That's what I use, too. Some folks are stymied about porting a propane tank at anything other than square on. So I was suggesting a way to put a hole in wherever you want at whatever angle needed rather than compromise your design intent because you can't get a hole saw to do it. It takes time, but a torch and grinder allows you to do what YOU want to do rather than settle for what one particular tool CAN do.


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## boatboy63 (Feb 27, 2010)

Not to take away from the main area of the thread, but I have a queston about cutting these tanks. If you use a propane or any sort of tank that was used for fuel storage, what are you guys doing to prevent the tank from exploding when you use a torch on it or drill and sparks hit the inside? I know I had an old gas tank that had a leak and I tried to repair it many years ago. I removed the tank from the car, drained it, flushed it completely with water, and then it jumped 6' off the ground when the torch hit it as I was about to solder it. The tank went from flat to a marshmellow as fast as my underwear went from clean to dirty.


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## ewdudley (Feb 27, 2010)

patch53 said:
			
		

> [This] is what I was thinking of doing. My buddy gave me a carbide bit hole saw to use so it shouldn't be too bad. he also has a big dremel-like tool that I can use to grind away some metal at the top and bottom of the hole so the coupling will fit in horizontally. I think I'm actually going to use a 2" double threaded coupling for the boiler supply line and run a diffuser pipe inside. I should be able to slow the flow down a lot with a short length of 2" pipe about 2 feet long before entering the tank, and then have it diffuse upward once in the tank. I'll only run about 3 feet into the tank though.



Lemme back-pedal some here.  _*Ideally*_ a diffuser pipe would run the length of the tank with a slot in the side.  For chilled water, where the differences in density are a lot less, getting things just-so really matters, but for hot water there's no need to sweat it much because the hot water will rise nicely unless you go out of your way to create a mixing jet.  

I think that if you just weld a fat coupling or pipe within a couple inches or so from the top of the end of the tank as it lays on its side, the fact that it points downward a little -- or substantially even -- will matter very little in the end and you really don't need run a diffuser pipe into the tank unless it's fun, easy, and what-the-hell-why-not.  

There's plenty of guys here who have plumbed into the top side of a horizontal tank, pointing straight down through a 1.5 inch coupling at 15-20 gpm (3-4 ft /sec) and it  stratifies just fine.


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## ewdudley (Feb 27, 2010)

DaveBP said:
			
		

> > You might be surprised, Dave, I know I sure was.
> >
> > Properly lubricated, those Lennox hole saws will walk an inch and a half hole right through 5/16’ steel much faster than I would ever have expected, on the order of two minutes or less.  If you don’t need a neat job the torch might be faster, but by the time you clean up a torched hole to be as precise as the drilled hole, the drilled hole is a faster and nicer.
> 
> ...



Oh I see.  I was proposing cutting perpendicularly with the hole saw and then hogging the hole out into an ellipse with plain old bastard rat tail.  For me it would be the quickest way to get to the point of having something easy to weld gas-tight, because unfortunately I've been known to overestimate my torch skills in the past.  Certainly better skills and tools would be preferable.


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## DaveBP (Feb 27, 2010)

> Lemme back-pedal some here.  Ideally a diffuser pipe would run the length of the tank with a slot in the side.  For chilled water, where the differences in density are a lot less, getting things just-so really matters, but for hot water there’s no need to sweat it much because the hot water will rise nicely unless you go out of your way to create a mixing jet.
> 
> I think that if you just weld a fat coupling or pipe within a couple inches or so from the top of the end of the tank as it lays on its side, the fact that it points downward a little—or substantially even—will matter very little in the end and you really don’t need run a diffuser pipe into the tank unless it’s fun, easy, and what-the-hell-why-not.
> 
> There’s plenty of guys here who have plumbed into the top side of a horizontal tank, pointing straight down through a 1.5 inch coupling at 15-20 gpm (3-4 ft /sec) and it stratifies just fine.



I'm with you, Eliot.
 Trying to minimize mixing at the ports into a propane storage tank can be enticing to those prone to obsessing about small details. I'm a good example of that.
Big pipe, top and bottom. That's pretty simple and probably all you need to know.
 If you have water returning to the tank from various loads with different temperatures it might get messy. Especially with solar heat input. I don't know what one would do in that case.
But for the boiler water going in at the top, after the tank has filled with hot water a bit, what's it going to mix with? More hot water. No large deal.



> ...what are you guys doing to prevent the tank from exploding when you use a torch on it or drill and sparks hit the inside?



Safest way to get the propane out is to fill it completely with water. That drives the propane gas out. Then drain and serve.


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## taxidermist (Feb 27, 2010)

I will know in a a couple of days as to how my tanks are mixing. With the help of Twofer from the site I have my Arduino working to read tank temps. He is working on getting me set up on data logging to show my systems performace. My secondary loop pump runs all the time so I know I get mixing but the hottest temps were still at the top of the tanks. I run into the top of the tank with 1" from the boiler and out the bottom with 1" return to boiler.


Rob


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## chuck172 (Feb 27, 2010)

Go to a welders forum. I think you'll get a different prospective on welding propane tanks. I know many here have done it and are still alive to brag about it. Me being one. Please just look into it. It's a good job to farm out!


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## DaveBP (Feb 27, 2010)

> Go to a welders forum. I think you’ll get a different prospective on welding propane tanks. I know many here have done it and are still alive to brag about it. Me being one. Please just look into it. It’s a good job to farm out!



The guy that's welding my propane tanks use to make his living welding Xray inspected nuclear reactor pressure vessels. I think it is a great job to farm out to someone who really knows their stuff. That would not be me as welder.

On the other hand, a fellow near here repairs propane tanks for one of the local propane dealers when they have a pinhole leak. He says he has them top them off with propane before he welds them. Talk about the courage of your convictions.! I guess if it's full of liquid propane it doesn't have room for air, huh? The arc is only running for a couple seconds and he knows where the leak is by the little yellow flame. Says he's repaired 5 tanks that way.


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## JayDogg (Feb 28, 2010)

Do you need to put copper heat exchange tubes in the propane tank? Or is it just to store the hot water coming from the boiler??  I want to buy a propane tank and make my own storage but dont know where to begin.  If anyone has taken pictures during their process of building there storage tanks and could send them to me it would be greatly appreciated.


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## taxidermist (Feb 28, 2010)

JayDogg said:
			
		

> Do you need to put copper heat exchange tubes in the propane tank? Or is it just to store the hot water coming from the boiler??  I want to buy a propane tank and make my own storage but dont know where to begin.  If anyone has taken pictures during their process of building there storage tanks and could send them to me it would be greatly appreciated.



No exchangers just the tanks to store the hot water. You can see some pics of mine in my blog.


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## patch53 (Feb 28, 2010)

I just talked to my buddy down the road and he said he has a tool that can measure the curvature on the side of the tank, and then he'll take the coulpings to work and cut them at the same angle/curve so they'll butt up flush to the side of the tank horizontally.  Should make it nice for welding I would think .

Pat


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## boatboy63 (Feb 28, 2010)

DaveBP said:
			
		

> On the other hand, a fellow near here repairs propane tanks for one of the local propane dealers when they have a pinhole leak. He says he has them top them off with propane before he welds them. Talk about the courage of your convictions.! I guess if it's full of liquid propane it doesn't have room for air, huh? The arc is only running for a couple seconds and he knows where the leak is by the little yellow flame. Says he's repaired 5 tanks that way.


Better be telling your friend goodbye before it happens. First of all, a propane tank isn't filled totally so it doesn't have any air. The most they fill them to is 80%. The other 20% is for expansion when the tank heats from the sun. His time is coming if he keeps doing it that way. I have seen local propane companies "burning off" tanks when they are trying to empty tanks. When they try to pump them down, it won't all come out so they hook a long pipe to it and light the end of the pipe. One of their techs told me that it will sometimes burn for several hours that way.


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## leaddog (Feb 28, 2010)

boatboy63 said:
			
		

> DaveBP said:
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He gets away with that because there isn't any air in the tank. just liquid propane and gas propane. with the tank full there isn't much room for the gas and there isn't enough air to suport combustion. Now with the tank empty and open to the air it has very little propane but lots of o2 and it takes very little propane gas mixed with o2 to cause a BIG bang. 
When they flare off the tanks the propane is mixing with the air at the end of the pipe and burns there. If they put air in the tank it might just swell up very fast and move to the other side of the country.
leaddog


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## DaveBP (Feb 28, 2010)

> He gets away with that because there isn’t any air in the tank. just liquid propane and gas propane. with the tank full there isn’t much room for the gas and there isn’t enough air to suport combustion. Now with the tank empty and open to the air it has very little propane but lots of o2 and it takes very little propane gas mixed with o2 to cause a BIG bang.
> When they flare off the tanks the propane is mixing with the air at the end of the pipe and burns there. If they put air in the tank it might just swell up very fast and move to the other side of the country.
> leaddog



I don't buy his explanation, either. I just thought it was a startling technique. 

The fact that we're still alive doesn't mean we understood every dumb thing we got away with.


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## ewdudley (Feb 28, 2010)

DaveBP said:
			
		

> > He gets away with that because there isn’t any air in the tank. just liquid propane and gas propane. with the tank full there isn’t much room for the gas and there isn’t enough air to suport combustion. Now with the tank empty and open to the air it has very little propane but lots of o2 and it takes very little propane gas mixed with o2 to cause a BIG bang.
> > When they flare off the tanks the propane is mixing with the air at the end of the pipe and burns there. If they put air in the tank it might just swell up very fast and move to the other side of the country.
> > leaddog
> 
> ...



No really, there's no death-defying stunt here.  Without oxygen you're golden.  After all, lighting an LP gas burner doesn't lead to a chain reaction back down the supply piping through the regulator and into the tank, kaboom.  As long as the area is ventilated enough to be sure that heavier than air LP hasn't pooled nearby, and as long as you're sure there's no oxygen inside the tank, how could you ignite an explosive mixture of fuel and oxygen?

Welding on an open empty tank is a different matter of course, especially with tanks that have had petroleum products in them because fuel can be present for years.  Filling with water can work if the tank is truly full.  Another technique is to put a dip tube to the bottom for exit flow and then pipe engine exhaust into the top so the warm exhaust displaces the cooler oxygen laden gases.  Calculate RPM of the motor times four-stroke displacement divided by two, convert to gallons per minute assuming exhaust volume is larger than displacement volume, and run the motor for a couple times longer than should be necessary, and have at.


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## DaveBP (Feb 28, 2010)

I got my tanks from a propane dealer. They "retire" tanks by filling them with water through one of the big fittings on the top (they're out back on a level lot) and pull all the fittings and hardware out of them and continue the water until it's squirting out all the holes. He was careful to give me these details to reassure me, I guess. Then they pump all the water out that will come out with their suction tube. They still smell pretty strongly. He said he couldn't trust some kids (with a death wish, maybe) from messing around with them.

I put a 1"  PVC pipe into them and ran air through them for a month or two sitting in the hot sun. No more stink.


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