Welding it "tight" (no weep hole)

[Sodo]

I was interested in the discussion about welding an item "tight" vs "weep hole". I was working on my gate yesterday and was looking at it, thinking about water and wondering if there was any inside it. My gate is welded "tight".

Drilled a hole and water poured out. It poured a lot more, that's how it looked by the time I dug the camera out. Recommend some folks drill drain holes in their "tight" implements and see what happens. Of course a little water in there might be more curiosity than problem (except near salt).

(EDIT: DELETED 2nd PIC with the large pee-stream BECAUSE i found where water can get in that one. The first one was welded tight, no nek'd eye visible entry points.

 

[CNC Dan]

Can you find where the water went in? Use a rubber tipped air gun to pressurize it and see if you can hear any air leaking out perhaps?

 

[LD1]

IF you cannot weld well, then leave a hole. If you are confident you can weld air/water tight, weld it solid. If no water can enter, there is no issues. A weep hole is a place for moisture (humidity) to get in as well as air and cause rusting. But better than allowing it to fill with water and no way out. So I guess my take is this

Best: weld it tight
Better: weep hole
Worst: what you think is welded tight, but isnt, and allowed to fill part way with water

 

[CNC Dan]

I'm not so sure.

Water doesn't realy create rust, oxygen does. Water serves as a catalyst to help take oxygen from the air and give it up to the steel.
But water alone won't cause rusting.
If you have water inside, but no air circulation you shouldn't have much rusting at all.
Kind of like a cast iron radiator in your home. It's full of water all the time but it doesn't rust.

 

[Shield Arc]

Quick and easy test. 3 or 4 PSI, and some soapy water.

 

[LD1]

I'm not so sure.

Water doesn't realy create rust, oxygen does. Water serves as a catalyst to help take oxygen from the air and give it up to the steel.
But water alone won't cause rusting.
If you have water inside, but no air circulation you shouldn't have much rusting at all.
Kind of like a cast iron radiator in your home. It's full of water all the time but it doesn't rust.

If water can get in, air can get in and you have rust.

Best not to let either in IMO.

Something designed for water, the water is added then the system is sealed. Yes, without air it wont rust. But unless you filled the tubes with water THEN welded them shut, air can get in the same way the water did

 

[Sodo]

(EDIT: DELETED 2nd PIC with the large pee-stream BECAUSE i found where water can get in that one. The first pic was surely "welded tight", no nek'd eye visible entry points.


Dan I'm real curious about this, but cant pressurize it as I hace cut other holes, which is come to think of it - is the real reason I thought it needed a drain hole. LD I could agree with what you wrote, until yesterday. Certainly it can be done, is done all the time. In 1981, I welded an aux fuel tank for a friend's pickup (MIG) out of 16ga sheet. It didn't have a single wet spot. It was "open" though. I wonder about the 'finish' when you weld up a closed cavity thats exhaling as you weld and starts inhaling the moment you stop.

I never would have imagined the volume of water, especially in 4 years. I paid a local $2,000 to build & install it as I could not do it at the time. Its 22 feet long and 100+ miles away. I doubt the fabricator gave more than normal effort to "weld tight", I suppose he could have if someone told him to.

Seeing how much water it held you can at least assume the lower welds were watertight (or became that way). Anyway thats why I suggested to folks to drill some holes and see if you find water too.

 

[Shield Arc]

I think where the average guy makes a mistake when welding up something that is suppose to be air / water tight. Is not feathering his starts and stops.

 

[Sodo]

Gotcha, that would help. Great pic says it all!

 

[Walkin Horse]

In the pipe fab shop I run we do a lot of structural support work. Anything that has a base plate on it gets a weep hole. Even condensation can build up inside of a capped pipe.

Sealing off a pipe or vessel is tricky. It always seems to want to poot just as you tie in. Sometimes it's apparent and sometimes you don't realize it. I always figured it was the hot expanding air blowing out.