k5s and 1/2 air flow?

I have a few questions perhaps one of you can answer about air flow. I have a K5la and I am currently running a 3/8" line to it. I have a regulator on it to keep the psi at around 125psi or so. I was wondering if it makes that much of a difference to run a 1/2" line to it?
I was also thinking instead of one 1/2" of using two 3/8". Is the air flow hampered any using two, or would it even make a difference?
So I guess in short, is a 1/2 needed? I’m so confused!

All trains 1/2" air line to horn valve then 1/2" to horn via a pipe nipple or air line. Via a big ole compressor that can recover quickly.Probably a big Wabco 3 headed compressor. Its not the big pressure you want all of the time it’s the volume of air. Your horn will blow on 3/8". I have did it to a K5 before but you are starving the horn. It would be just as easy to change the 3/8" line to 1/2" then it would be to make a fitting up to run two 3/8" lines. It would work. But if ya put all the time, money and effort in a project I would do it the cleanest way.

Good Luck,


Thanks John.
Thats’s kind of what I thought, just wanted to confirm. I’m not running a Graham White or any other manual valve. I’m running a standard ol solenoid.
Thanks again.

My Shockers were starved for air on a 3/8" rubber air hose line. The volume just about doubled when I went up to 1/2" rubber air hose. I would never run a Nathan on anything less and would probably upgrade to 5/8" ID rubber air hose and fittings.

What about pushing 2 - 1/2" lines to it? If I’m not mistaken there are 3 ports on the L and H manifold… 1 on each end, and 1 on the bottom… not to mention one on the “back” of the H manifold…

You would have to get 2 solenoid’s to do it that way, but the horns wouldn’t starve… I’m thikning about doing it that way once mine get here… If I do, I’ll post up some pictures…

I appologize for jacking someone’s pictures, but I needed it for demonstration purposes… I will post pics of mine when they get here (next week)

Thanks Guys,
I knew I’d get ideas from all of ya. I going with the 1/2" upgrades.

Using two 1/2" ID lines might work but there could be several problems with this:

  • Two valves = more money.

  • Two lines = more time and hassle to install, takes up more space.

  • Double the number of fittings and hose length = twice as many chances for leaks.

  • Unless your lines and valves are absolutely identical and the valves fire at the same time, one line is bound to be little higher psi than the other, in which case it will over power the other line just a bit which may result in some strange airflow patterns or even a minor vacuum situation which reduces the total psi sent to the horns.

Why not just go with one 5/8" ID hose and fittings? All of this stuff is easy enough to find and not too expensive.

I have been thinking of doing a duel valve system. The electronic solenoid on the 1/2" and a manual (perhaps a Graham White) running on the 3/8". Yes, I know it might become a headache. But that’s half the fun, making it all work out.
Just food for thought.

That is correct, but it may be easier than finding 5/8 id air line…

run them at the same time

You are absolutely correct, but there is also a chance that your original install could leak

Use a check valve coming off of the horn manifold. more expensive, but you wouldn’t have that “Back Pressure”

I have yet to see anything around my house (or city for that matter) larger than 1/2" OD tubing that will hold any kind of pressure. I actually had to go to a hydrolic shop to get the 3/8 air line I used for my air source relocation kit…

Many stores such as Lowes, Home Depot, plumbing supply, pneumatic supply, repair centers, etc. should have it but if not then you can order the hose online from thousands of retailers. If you insist on buying locally and have trouble finding 5/8" near you then step up to 3/4" which is probably more common. Don’t just look in the pipe or plumbing section, also check the air tools, fittings, garden, automotive, etc. In Lowes I found a number of things I needed scattered in different sections throughout the store.

Of course, but it will still take more time, cost more, and take up more space than installing one line. If you are bored then have at it. :slight_smile:

Any system can leak but a system with twice the fittings and joints is much more likely to leak and troubleshooting it would take more time. Plus the air line resistance is greater with more hose and fittings. Again, have at it if you are determined.

Good option if you run two supply hoses to your manifold. Use a check valve on both. But of course you would need to find a large ID check valve with high flow capacity, which may be difficult and costly.

See comment above. Good luck!

Why you always gotta make sense… :slight_smile:

At Ease Guys,
I made a decision and bought my 1/2" stuff today. I’m going 1/2" for a multitude of reasons. None of which make sense to me. Kidding!

  • My primary reason is authenticity. I want it to sound as true as if it were
    comming down the tracks.
  • Secondary is maintenance and simplicity. K.I.S.S (Keep It Simple Stupid)
    I was taught to “Work smart not hard.”
  • Thirdly … can’t think of a thirdly. Wait … I got it!
    I’m a lazy SOB. Much easier.

Ok Guys,
Back to you battle …

K I S S An oldie but A goodie.I look it this way, Never enough time to do it right but always enough time to do it over ! I like to do the job ONCE (The right way) !

Now for my next questions. Is there an acronym for acronym? Or, why is the word abbreviation soooo long? What is another word for thesaurus? Where would I go to find the definition of Dictionary, if I had never heard of one?

LOL You’re A funny guy ! Google it I guess :smiley:

The extra ports on a K5 and K3 manifold aren’t half inch by the way and adding line to these ports won’t help. A train doesn’t have more than one line to it’s horn’s manifold.

What I was saying… is if you use 2 - 1/2" lines, you can move more air than with 1 - 1/2" line… from what everyone is saying, the K series horns like VOLUME, not PSI… so if you can move more volume through your horn by using 2 of the ports, why not do it that way vice trying to find 1 huge 5/8" hose to use?

Not to mention the ports on your air tank are only 1/2" to begin with… I know you said they are not 1/2" ports on the manifold, and I see that, but that would make them probably about 3/8" ports… so now you have to use a smaller hose (or find a clamp big/small enough to fit on your port and manifold)

I see what you’re saying but, contrary to popular belief, they aren’t really any kind of air hungry, be it volume or pressure. I’ve blown mine on 1/4 inch line at 125 psi and it was still very loud. Listen to a real train with a K3…They only have one 1/2 inch line going to their horn at roughly 130 psi. Why use 5/8 inch line when there’s no real need for it or more than one airline?

I agree with you ! If your horn sounds normal and the sound doesn’t trail off and the note is correct why try to reinvent the wheel. Put A air pressure gauge on manifold and check to see if the pressure drop exceeds the 15 PSI from tank pressure while honking the horn. I read this somewhere in the Nathan Mfg.notes.
If you need A louder horn than A Nathan, You need A ship horn. LOL