If they are horizontals they are exempt. If they are vertical 20 pounders
you can have the valve changed out for about $30 at any propane distributor.
You can buy a replacement OPD at Northern Tool for $15 but they are a PITA
to install unless you have a way to grip the tank.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

wrote in message
...
I have bought a boat with two large aluminum propane tanks. But they do
not have the newer OPD valve. Can these be updated? I'd like to keep
them given the cost of new tanks. I'd prefer not to use the cheaper
steel ones.