The Solinst 408M Micro Double Valve Pump miniaturizes the same double check-valve pumping principle as the 408 into a flexible, coaxial-PTFE tubing assembly only 3/8" in overall diameter. A small filter/pump body at the intake — fitted with a sintered 316 stainless steel 50-micron screen — feeds formation water into both an outer annular drive line and an inner 3/16" sample line. Compressed gas cycled down the annulus by a surface control unit closes a lower check valve and forces the water in the inner tube up to the surface; venting the gas lets formation pressure reopen the lower valve and refill both tubes with fresh water, while an upper check valve prevents the sample from draining back. Its narrow profile lets it fit inside 1/2" ID tubing, making it purpose-built for CMT multilevel monitoring channels and other small-diameter installations.

Do you have everything you need? The 408M requires a separate compressed-gas source and control unit — such as Solinst's 464 Electronic Pump Control Unit — to drive its cycle; it does not operate on its own. Each assembly is supplied as a complete pre-configured length (tubing, filter, and manifold included) and can also be field-spliced for custom depths. Multipurge manifold parts are available in the Solinst CMT Multilevel System Parts & Accessories collection.