Official 2005 DOT Regulations
There are blanket rules, and exceptions for the the blanket rules. First, the blanket rules.
1 - All fiber-wrapped tanks are to be hydrotested every 3 years, unless the manufacturer specifically indicates ON THE BOTTLE that hydrotesting is due at 5 years. All fiber-wrapped tanks have a maximum lifespan of 15 years, no exceptions.
2 - All steel and aluminum HPA tanks are to be tested every 5 years, with an unlimited lifespan. The only exception to this rule is for steel tanks stamped 3HT, which must be tested every 3 years and have a 24 year lifespan.
Again, first the blanket rule.
1 - All CO2 tanks (with one exception, see below) must be hydrotested every 5 years, with unlimited lifespan. The only exception is for tanks under 2 inches in diameter and less than 2 feet in length, these are exempt from testing. NOTE - Chrome-Moly tanks are NOT exempt from testing!! There is a wide belief in the paintball industry that they are exempt, they are not, unless they fall under the 2 inch diameter rule. The 2 inch/2 foot rule will apply mostly to 9-ounce tanks.
There are some "E" codes stamped on some fiber-wrapped HPA bottles and chrome-moly tanks. Many people believe that if their bottle is stamped with an "E" code it means they are exempt from testing, this is not true. It means that bottle falls under an exemption from the blanket rule in some specification, but that exemption may or may not address the hydrotest date. Here are the only listed "E" codes for fiber-wrapped tanks on the DOT site, and how they will affect your bottle.
E-8096 - manufacterer Scott, some CO2 bottles are exempt from ever needing to be tested, for their service life of 15 years. These are for 16 ounce chrome-moly tanks.
E-07277 - manufacterer SCI, to be tested every 3 years, 15 year service life. This exemption deals with the manufacturing process, not the hydrotest schedule.
E-09634 - manufacturer Luxfer, to be tested every 3 years, 15 year service life. This exemption deals with the manufacturing process, not the hydrotest schedule.
E-10915 - manufacturer Luxfer, may be changed to 5-year schedule, this will be explained below.
E-10945, manufacturer SCI, may be changed to 5-year schedulue, as explained below
E-11005, manufacturer Careton Tech, to be tested every 3 years, 15 year service life. This exemption deals with the manufacturing process, not the hydrotest schedule.
E-11194, manufacturer Careton Tech, may be changed to 5 year schedule, as explained below
E-12479, manufacturer Luxfer, to be tested every 3 years, 15 year service life. This exemption deals with the manufacturing process, not the hydrotest schedule.
5-year test schedule exemption explained - All these bottles still have a maximum service life of 15 years from original manufacture. These bottles were originally manufactured under a 3-year retest schedule, but the manufacturer was allowed by the DOT to move them to a 5-year retest schedule, provided they have been tested/manufactured after a certain date, as applied below.
For exemption code E-10915, if the last test date was before May 11, 2001 then your bottle is still on the 3-year cycle and must be tested every 3 years. If it shows a test date after May 11, 2001 then your bottle is now on a 5-year test schedule.
For exemption codes E-10945 and E-11194, your bottle is on a 3-year test schedule if the last test occurred before July 1, 2001. If your bottle has been tested after that date, you are now on a 5-year test schedule.