I am new to this and have bought a K3LA from ebay. I have bought a 1/2 ball valve. The hole in the ball valve is bigger than 1/2. Almost 5/8. My question is what size of airline should I use? I can’t find plastic dot airline that is 1/2 ID. The ID is under 1/2. If I buy 5/8 the ID is between 1/2 and 5/8. So 5/8 airline would match the inside ID as the ball valve. Or should I just buy the 1/2 OD airline ?? I will be running a 10 gallon air tank around 140psi. I blew these horns at a shop with a 1/2 rubber airline at 150psi and they were VERY loud. Will I get the same loudness from a smaller air tank with whatever airline that is recommended 1/2 or 5/8? Thank you 
Home Depot sells 1/2" ID 200 psi orange hose by the foot. I would just use that. Thats what I have been using with my K5, Leslie, and K3 for 3 years and no problem.
1/2" pipe thread is always going to measure larger. Your 1/2’ fittings going into the ball valve will measure almost 5/8… I bought 1/2" o/d air line for my k3. havent hooked it up yet but thats what most people use. It will be loud 
I just came from home depot, they don’t have any dot airline, only 3/8 rubber airline. So I went to a tractor trailer shop and they have dot airline, they have 1/2 but it is od not I’d. We measured the inside and it was almost 3/8. We measured 5/8 airline and the inside was just a little less than 1/2. Then we measured the fittings for the 5/8 airline and it restricts down to 3/8 Id. Pipe is too hard to work with. I have to bring it from the back of a Montana van all the way up to the drivers seat and back to the back again. What fittings do everyone else use? Thanks for the replies. I live in Ontario Canada, maybe that’s y I can’t find 1/2 Id ?
DOT Tubing is measured OD.
Rubber hose is measured ID.
Didn’t Home Depot have 1/2" airhose? That’s good you’re considering the fittings’ ID also. I think that gets overlooked a lot as a restriction. I’m going to hunt for big fittings when I finally get to mine. There is another thread about this somewhere…
No 1/2 rubber hose at home depot. I do have some 5/8 rubber airline with 1/2 Barbed fittings around here, I haven’t tried it yet. Is 5/8 too big? I am going to see If I can have some 1/2 airline made up with 1/2 NPt fittings that are not restricted. I have read on here that I should use all the same size airline and fittings, so that’s what I am trying to find.
I tried the rubber airline (like you would use for shop tools). Any of the lines that stay pressurized swelled up in a few months. So I would recommend DOT for lines that are directly tied to the tank. For the lines between the solenoids and horn, you can probably get away with just about anything that has a working pressure that equals or exceeds your system’s pressure.
I remember the thread that stuck around for some time about how small ID changes gave significant improvements in the horn’s operation. I haven’t been able to find it, but it had alot of opinions on hose / fitting sizes.
Go to Lowes; They have 5/8 ID black hose, rated to 200 psi. Then, go to home depot and get a 5/8" barb to 1/2"npt brass fitting. I also use lowes’ 3/4" crimp clamps with crimping tool. The tool is about $10, and the clamps are $2.50 for 10, and they work much,much better than screw clamps, especially if you use two of them to clamp the hose to the barbs. The screw clamps usually break before you can get them tight enough. This is what feeds my Leslie S5T with maximum orifices, and it never starves for air.
^^^I like the sound of that.
Lots of reading in here:
http://www.trainhornforums.com/showthread.php?t=2327&highlight=fitting+restriction
That sounds good. I already have 5/8 ID rubber airline, I think I already have 5/8 barbed fittings. It fits on the 5/8 line anyway. I was just following what others have posted on here about using 1/2 airline. The fittings restrict down to 3/8 besides the ID of the dot airline is not even close to 1/2. So it didn’t make sense to use it, but it must work too. I like the bigger airline. I just didn’t find any posts on here using 5/8 line, so I thought maybe it is too big. Thank you for all the replies.
Really no such thing as too big, other than aesthetics or space limitations. With gases(air), a bigger line does not increase pressure, and cfm is regulated by what the device uses. It’s essentially the same as electrical wire; the bigger the wire, the less resistance or impedance, and the greater current-carrying capacity.
Ok thanks for the info
What You Said Joseph,
All I can say is I think it’d be a Moster at 5/8"! Here’s my K5 on 1/2"od, 165 PSI.
What You Said Joseph,
All I can say is I think it’d be a Moster at 5/8"! Here’s my K5 on 1/2"od, 165 PSI.
Wow that’s a huge difference Diesel Sniper. I just blew my K3LA at 120 psi with the 5/8 line with 1/2 fittings and WOW is it loud. Just as loud as it was with the 1/2 line at 150psi in the shop, I can’t tell the difference anyway between 120 and 150. Thanks for all the help. It is very loud now.
COOL. Wanna see wanna see! Wanna Hear it tooooooo. My turn to push the button! Not your turn! My turn!. LMAO
LOL. I will take pictures sometime this week and a video too. My neighbors are probably mad at me right now lol. I don’t have it on anything right now, just a portable air tank with the line running to the horns. I want to strip the paint off of the tank and either polish it or paint it before I install it on my montana van.
I went to Lowes today. Are you talking about the “PEX system” clamps? They look really sensitive to the finished diameter since you ratchet the clamp one tab at a time. What if you’re in between tabs - like one is too loose, but you can’t reach the next one? The 5/8" ID hose is 1" OD. Does a 3/4" clamp start out big enough to fit over that?
The tools I saw were $39, $79, and $89. They have a cheaper one?
Just want to make sure we’re talking about the same thing & the sizes you listed weren’t a typo…
Thanks
EDIT: I just realized that I was looking at ‘cinch’ clamps & they also have actual ‘crimp’ rings… Which did you use?
I used these crimp rings. http://www.imperialinc.com/items.asp?item=0699790 They work good. I just used vice grips to crimp them. They were 5/8 rings. At first I had a leak near the tank, but I crimped them more with vice grips and I have no leaks.