Promax has one of the most versatile and highest-quality ranges of underground tanks in New Zealand. Our underground stormwater and underground wastewater tanks are designed for the effective retention or detention of stormwater or secure and reliable storage of potable water. Each Promax underground tank is engineered by geotechnical experts and Finite Element Analysis tested (FEA). Our plastic detention tanks are thoroughly tested and made to withstand ground and water pressure at depth. All this means underground tanks you can trust in a wide variety of settings, including under driveways, footpaths, car parks, forecourts and much more.