Adding a dump valve on spread axle

[free2fly973]

I'm trying to add a dump valve to a spread axle trailer that already has a pilot valve that dumps when trailer break is set. Supply line to top of pilot. Driver side inlet to ONLY leveler ( not yelling just stressing one leveler for whole trailer), bottom pilot outlet to first air bag and T's from each air bag to next for all four bags.
Im wanting to add the dump to the back axle. I added it to the T going to first back axle bag, then T to second back bag. But when I flip switch it dumps all bags. ??. Guess missing some parts or air line plumbing. Will someone please ahead some light for me? Thank you all

[Chain Drive]

you said the bags are all tied together, you will need a one way valve to separate the front from the back

[DEMO]

I'm trying to add a dump valve to a spread axle trailer that already has a pilot valve that dumps when trailer break is set. Supply line to top of pilot. Driver side inlet to ONLY leveler ( not yelling just stressing one leveler for whole trailer), bottom pilot outlet to first air bag and T's from each air bag to next for all four bags.
Im wanting to add the dump to the back axle. I added it to the T going to first back axle bag, then T to second back bag. But when I flip switch it dumps all bags. ??. Guess missing some parts or air line plumbing. Will someone please ahead some light for me? Thank you all

Search for skateboardman posts. He added one and tells you how.

[free2fly973]

Ok. That's kinda what I was thinking. But not for sure. Haven't heard of one. I'll check local truck parts store in morning (Weldon's) and maybe the TA shop to see if they have something like that. Thanks for your help and wisdom. I really appreciate it. If any other ways I'd like to hear them in case I can't find oneway check valve anytime soon. I'll look online for one.

[free2fly973]

Thanks. I'll search for skateboardmans posts too

[free2fly973]

I went though 23 pages of Skateboardman post w/ 10 or so posts per page. I didn't see the post on dump valves. I'll look again later when got more time. Thanks for you guys help. I'll keep at it

[not4hire]

A one-way, or check, valve won't do the job. You need to isolate the rear bags from the front when you dump the air. A one-way valve just prevents air from travelling against the flow direction (reverse of normal flow). Such a valve would also upset the balance between the front and rear bags as it would prevent air from being dumped from the rear bags during normal operation.

[kwswan]

If the lines going to the rear bags are tied in with the front ones then you will need a valve for each side.
I have two trailers that have dual leveling valves & this was how they had to be hooked up to work,one of these had the valve to dump when parked.

[Semi Crazy]

Hey Kwswan, was that you I chatted to going thru the guitar on 440 last year?

free2fly get rid of that auto dump valve. set it up right.

How to plumb air bags:

Air should come from tank to pressure protection valve to manual 3-way ball valve (to dump all four) then to height control valve to electric 3-way valve (for dumping rear only).

On electric 3-way valve one port goes to front bags, one to rear bags and other to atmosphere.

Here's link to good electric dump valve that I use. http://peterpaul.com/valves/3-way-di...ontrol/1752-2/

P/N for manual dump 3-way ball valve is Hendrickson number AK-147-1 but other trailer mfrs have this same valve under different numbers. I have a hard time finding anyone who carries it any more. They'd rather sell you a push-pull type with o-rings.

Auto dump is not good, you should dump air first, then when bags are empty is when you set brakes. This avoids force against bushings and brake shoes when brakes are applied before trailer has a chance to lower.

[kwswan]

Yep that was me.