Is it possible to contaminate the membrane and filters by placing drain under pressure in order to clear and forcing water out the overflow on the side of the faucet of the whre 25 Reverse osmosis system

OK, now I understand. First, on the Reverse Osmosis Membrane Housing Outlet Ports there is only a Check Valve attached to the Permeate (Pure Water) Port, not the Concentrate Port (Drain Water). The Permeate line is what fills the storage tank, so you don't want back pressure from the tank reversing into the membrane filter which could severely damage it. So, there is a high Risk for Sewer Water to Back-flow into the Membrane Filter and Contaminate it as it is discharging water to the sewer drain if there is any noticeable pressure restriction in the drain distribution manifold. Second, this is why "Air-Gap" Faucets are supposed to be used when installing Reverse Osmosis Systems. With an Air-Gap Faucet, there are three (3) attachments for tubing at the base of the faucet, and a small hole drilled out underneath the lever or handle of the faucet. The 1/4" pressurized drain line tube from the RO System attaches to the 1/4" barbed fitting under the faucet base, then a 3/8" drain line tube attaches to the 3/8" barbed fitting. So when the drain water is pumped up to the faucet under pressure, it returns to the sewer line under Gravity, or No Back Pressure. Then, if the plumbing becomes restricted in any way that the RO Unit can't drain into the sewer under gravity feed, the hole drilled in the base of the faucet allows the back pressure to be escaped to the atmosphere, and if necessary drain water out of the hole until the plumbing pressure restriction can be resolved. This eliminates the possibility of a reverse flow pressure situation from occurring. Hope this helps, and you can always visit us online at www.puresafe.com We have filter cartridges for all makes and models of RO Systems, and 1/2 micron filters that no one else in the trade is using at this time. Thanks, Victor