When you want to add a basement sink, but you are not up to breaking into a concrete floor to install a pit liner, consider installing an above-floor sump box, available at most Boise plumbing supply or home improvement centers. According to the most referred Boise plumber, the box receives the water from the sink drain and pumps it away like a sump pump installed below the floor.
You will have to tie the discharge side of the box to the house drainage system and this installation will also require a vent pipe that extends above the roof. Follow these 7 tips or call your qualified Boise plumber for a professional installation.
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Tip #1 Place the box on the side of the sink where the discharge connection to the house waste system is most convenient. Install a male adapter in the side of the box. Attach the trap to the bottom of the sink, and connect the two with pipe and fittings.
Tip #2 Attach a threaded plastic pipe nipple into the top of the sump unit. Use thread-sealing tape to make sure the joints don’t leak. Lower the unit into the box, positioning it so the pipe nipple can extend through the hole provided for it in the box lid.
Tip #3 Place the cover on top of the box, and push the rubber gaskets into the holes for the cords and pipes. Use the bolts or screws provided in the kit to install the lid. Tighten these fasteners progressively, turning each about one full turn before moving onto the next.
Tip #4 Install a threaded coupling on top of the threaded nipple, using thread-sealing tape again. Thread a check valve into the top of the coupling, and tighten it in place with groove-joint pliers. This valve prevents wastewater from backing up in the sink.
Tip #5 Use 45-degree elbows to offset the vent and discharge pipes toward the wall. To provide power, install a single-outlet 120-volt receptacle near the box. Connect the receptacle to its own 15-amp GFCI-protected circuit.
Tip #6 The most convenient place to splice in the sump box discharge pipe is in the main waste stack. Cut out a section of pipe, and replace it with a 3-inch Y-fitting with a 1 1/2-inch hub on the side. Add pipe nipples to the Y, and install it with banded couplings.
Tip #7 The easiest way to vent the sump box is to connect its vent port to an existing dry vent line. Install a T- or Y-fitting in the vent piping, and join the hub on this fitting to the adapter that is installed in the sump box with a combination of pipe sections and fittings.
PLUMBING TRADE SECRETS: A sump-box kit won’t handle a lot of volume. It will work for a laundry sink; an ejector sump pump will be needed if a toilet will also be added to your system.