No-Purge sampling can be defined as sampling groundwater from a well without any removal of water before sampling. This sampling method is gaining acceptance by many regulatory agencies. Methods are based on the principle that groundwater that flows through a screen into a well, maintains equilibrium with the adjacent water bearing unit. Sampling at the screened interval should result in representative samples, without the need for purging.
When compared to conventional sampling methods, no-purge sampling can eliminate health and safety concerns, as well as reduce costs. There is no purge water to handle or dispose of, and the equipment required is typically simpler and easier to transport. Less labour and shorter sampling times are also benefits.
The Model 425 Discrete Interval Sampler is a no-purge instrument that allows groundwater sampling from specific depths, without mixing of water from different levels. The stainless steel sampler is pressurized before being lowered to prevent water from entering until the desired zone is reached, pressure is released and the sampler fills with water from the discrete zone.