Fire and Emergency NZ says new safety measures mean firefighters can once again pressure test fire hoses.
Last month, a firefighter was seriously injured when a hose burst while being pressure-tested, and Fire and Emergency stopped all testing.
New guidelines were issued last week after an initial investigation.
Hoses must be cleaned, dried and pressure-tested before being used at fires.
Fire and Emergency's national operations manager, Paul Turner, said firefighters must now stay at least 10 metres away when testing the hoses.
They must also make sure the hose is laid in a straight line and, when the testing's done, release pressure at the pump before anyone approaches the hose.
Despite those assurances, the Professional Firefighters Union national secretary Wattie Watson is warning members not to perform the tests until the investigation is completed.
"It's not just about the hose failing but about why the firefighter got injured because it failed, we still don't know because the investigation is yet to report what actually happened for that firefighter."
Ms Watson said some centres are running out of usable hoses, and firefighters there should take every precaution when testing those hoses.