They no longer do the testing.
http://www.naturescomfortllc.com/boiler-warranty/Treatment & Testing
Your boiler must have "Nature's Comfort Boiler Treatment" added during initial filling with water, antifreeze or glycol and must be tested when first filled and then annually at the end of a heating season to ensure proper concentration (1,000-1,5000ppm recommended, 500ppm minimum of Nitrite) for your warranty to remain valid. The water jacket must remain full of properly treated water at all times after installation save for draining, flushing and re-treating. Minimum recommended initial mix ratios for each boiler is: NCB120 - 1.5Qt; NCB175 - 1.5Qts; NCB250 - 2Qts; NCB325(G) - 3Qts, GT220 -2Qts, GT-500 -3Qts. There is no maximum limit. Contact Nature's Comfort or your dealer to obtain water treatment. You must have your water tested for nitrites by your dealer or you may order a more comprehensive test from Wood Boiler Solutions LLC to also satisfy warranty requirements. Order online at
www.woodboilersolutions.com using promotion code "NCLLC" to receive a 15% discount or you may order over the phone. Always request results to be sent to you and you must keep them on file to show proof of treatment and testing if warranty work is ever needed. Testing done by anyone other than a dealer, Wood Boiler Solutions, a certified lab or Nature's Comfort will not be accepted for warranty claims but is encouraged for monitoring treatment levels to obtain the maximum life out of a Nature's Comfort boiler, particularly if water is being added throughout a heating season. Nitrite test kits are available from your dealer or Nature's Comfort.