I believe acceptance testing per the current edition (2013) of this standard is governed by the formula for make-up water as Q=LDP^.5/148,000. I happen to have a 1994 edition of this same standard that you would see appears differently, at Q=NDP^.5/7,400. "Q" in both equations/versions is in effect the amount of make-up water in gallons per hour that must be added to the pipeline to maintain the pressure to within +-5psi of test pressure P in psi, "L" in the current version is the pipeline length in feet, whereas the different "N" in the 1994 version is instead the number of joints in the pipeline. The formulae look drastically different, until one realizes the most common type of pvc pipe in the USA is gasketed joint and in 20 feet lengths, and if you multiply the denominator of the 1994 equation by 20 you will in fact get the 148,000 denominator value of the current (where "N" has been replaced by "L"). In practical terms, very likely close to the "same difference". [I did see the units definition of "P" in the metric version of the testing equation in the 1994 edition of "killivolts per ampere" (that I fear may have confused at least a few of us civil engineers worldwide for some interim period!) appears instead in the latest edition as "kilopascals".]
That being said, while the amount of make-up water in a leakage test appears similar (and I guess I would be surprised if any intermediate version e.g. 2005 were different in that regard), there are some perhaps more subtle variations in other test duration/descriptions or requirements per the standards that may or may not be of any interest to or effect on some Owners. Hope this helps, and as I unfortunately do not have the 2005 version, I will like you await more learned comment.

I was able to obtain a copy of the old standard, C605-05.

It reads as follows in "7.3.5 Test Pressure. The hydrostatic pressure shall not be less than 1.25 times the maximum anticipated sustained working pressure at the highest point along the test section unless the pressure exceeds the design pressure limit for any pipe, thrust restraint, valve fitting, or other appurtenance of the test section."

The new standard, C605-13 reads as follows in "Sec. 10.3.5 Test Pressure. The hydrostatic test pressure shall not be less than 1.25 times the stated anticipated maximum sustained working pressure of the pipeline measured at the highest elevation along the test section and not less than 1.5 times the stated sustained working pressure at the lowest elevation of the test section. However, in no case shall the test pressure exceed the rated working pressure for any joint, thrust restraint, valve, fitting, or other connected appurtenance of the test section."

I have a couple questions concerning the latest standard. 1) What is the difference between "anticipated maximum sustained working pressure" and "stated sustained working pressure"?; 2) If the test pressure at the lowest elevation is 1.5 times the stated sustained working pressure, won't the test pressure be greater than 1.5 times the sustained working pressure at a higher elevation of the pipeline?; and 3) Is it the intent of the standard to have the test pressure at the higher elevations be greater than 1.5 times the sustained working pressure?

Thanks for your thoughts on this.

Uhmm.. It seems like more and more words are being added to some hydrostatic testing specifications. In partial answer to your more specific questions, I did see the early portion concerning changes to the latest version of the standard stated:

"Hydrostatic pressure testing requirements were changed to include the following: “not less than 1.5 times the stated sustained working pressure at the lowest elevation of the test section shall be required..."

I did notice also that now in the introductory area of this standard, in a section headed, "The following items should be provided by the purchaser..." there is also now a quite lengthy list of things to be so provided (maybe not really by the standard but instead?) by "the purchaser". That list now includes,

"21. System design pressure, required test pressure, and test duration (Sec. 10.3.5 and Sec. 10.3.4)..."