Step 1: Mount the filter housing assembly
Mount the iSpring 3-stage pre-filter housing to the cabinet wall or back using the included L-bracket. Position the housing so the filter canisters can be unthreaded downward without hitting the cabinet floor -- leave 6-8 inches of clearance below the housing. The housing should be mounted so the inlet and outlet tubes route cleanly to the supply T-valve and to the RO membrane housing (Stage 4). Use the template in the iSpring documentation to pre-drill mounting holes at the correct spacing for the 3-canister assembly.
Step 2: Install the supply T-valve
Turn off the cold water supply under the sink. iSpring includes a feed water adapter that connects to the cold water supply angle stop valve. The adapter T-branches to: (1) the original line to the kitchen faucet and (2) a 1/4-inch supply tube to the iSpring Stage 1 filter housing. This connection requires no cutting of supply lines -- the existing angle stop valve stem is removed, the adapter inserts into the valve body, and the valve stem re-inserts through the adapter. This is a non-destructive installation that can be reversed completely.
Step 3: Install the storage tank and drain line
Connect the pressurized tank to the tank port on the system manifold using the 1/4-inch tubing. Verify the tank pre-charge pressure is 7-8 PSI using a tire gauge on the tank Schrader valve (the Boyle valve stem on the tank base) -- iSpring tanks ship pre-charged at this pressure, but verify before installation. Connect the drain line (1/4-inch tubing) from the system drain port to the drain saddle clamp on the sink drain pipe. The drain saddle clamp connects to the tailpiece of the P-trap -- drill a 1/4-inch hole in the drain pipe, mount the saddle, and insert the drain tubing.
Step 4: Drill the faucet hole and first flush
The dedicated chrome faucet mounts through a 1.38-inch hole in the sink deck or counter. If no pre-drilled hole exists: for stainless steel sinks, use a step drill bit with cutting oil; for composite sinks, use a sharp-point hole saw with the manufacturer-specified drill speed. After the faucet is installed, open the supply valve and run the system for the first flush: allow the tank to fill (approximately 2-3 hours), then draw and discard the entire first tank volume through the faucet. This first flush removes carbon fines from the pre-filter stages. After the second tank fills, water is ready for drinking.