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DIY Tips For How To Install A Basement Laundry Sink

By on Mar 28, 2016
DIY Tips For How To Install A Basement Laundry Sink

If you've ever wanted a laundry sink but couldn't come up with a way to drain it, you're not alone. Most older homes have inadequate plumbing, especially when it comes to laundry drains. Often there's only a trapped drain in the basement floor. And many basements, both old and new, have no below-floor drainage piping at all. These are common problems with no easy solutions.

Of course, the best approach is to break open the basement floor and install new drain and vent piping, but this is not always feasible. Another good alternative, especially when the sewer exits through a basement wall, is to break open a smaller section of flooring and install a below-grade sump pit and pump. Or, you could do what we did, which is install an above-floor sump box and pump, designed especially for laundry sinks.

Equipment Overview

Our home is not that old, but we wanted a laundry sink on a wall opposite the existing plumbing stack. Bringing new waterlines in overhead was not a problem, but an above-floor drain line was out of the question. An overhead discharge line was our only option.

We chose a single-tray, floor-mounted laundry sink for about $60, and an above-floor sump package for about $150. This contained a sump box, 1/3-hp pump and check valve. We fitted the sink with a utility faucet that cost about $40 and we used Type M 1/2-in. copper tubing and fittings for the supply lines and 1 1/2-in. DWV plastic pipe and fittings for the drain lines. All these parts should be available at well-stocked plumbing supply stores and home centers.

The plumbing hookups for the sink and sump are pretty basic, but keep in mind local plumbing codes. You'll need to vent the sump box and tie the waste line into an existing stack, using a wye fitting. Some codes may allow an automatic vent device, but most will require a dedicated vent that either ties into an existing dry vent or exits the roof independently. As for the waterlines, soldered connections are acceptable under all codes.

Setting the Sink

Start by threading the faucet spout into the faucet base and tighten the spout's retaining nut. Then, fit the faucet base through the deck holes in the sink and tighten the jamb nuts until the faucet is secure. Fit a flanged PVC tailpiece over a nylon insert washer and tighten the plastic nut against the drain fitting on the bottom of the sink. Follow this by attaching two 24-in.-long, ball-head copper supply tubes to the faucet base shanks and tightening the nuts until they're snug. Finish up by inserting the metal legs into the sink's corner slots.

With the sink ready, start running the waterlines. Solder lengths of 1/2-in. copper pipe into brass drop-eared elbows. Next, using hollow wall anchors, attach the elbows to the wall next to the sink, about 16 in. below the rim.

With waterlines in place, thread 1/2-in. close nipples into two chromed angle shutoff valves. Then, install the valves in the drop-eared elbows, using Teflon tape to seal the threads. Tighten both valves with an adjustable wrench.

Because laundry sinks are fairly lightweight, they can be easily knocked around with rough use. As such, most sinks come with anchor brackets that allow you to fasten the legs to the floor. To install these, first drill anchor holes in the floor with a masonry drill bit. Then tap plastic anchors into the holes and screw the brackets to the floor. Finish up by bolting the sink legs to the brackets.

With the sink anchored in place, carefully bend the supply tubes to meet the shutoff valves that are fastened to the wall. Trim the tubes to length and slide a nut and compression ring onto the end of each. Then, insert each tube into its valve port, lubricate the compression rings and threads with pipe joint compound and tighten the nuts about two full rotations past finger-tight.

Installing A Sump Pump

Begin by threading a 1 1/2-in. plastic male adapter into the sump box, using Teflon tape on the threads. Then, apply PVC cement to the hub of the adapter and slide a short stub of pipe into place. Follow this by gluing two 45° elbows and a ground joint adapter in place. This offset arrangement should meet the sink's drain line nearly head-on.

Move next to the sump pump and its piping. Our pump came equipped with a 1 1/4-in. threaded male outlet, a 1 1/4-in. coupling and a check valve with a barbed fitting on top. Assembled as shipped, this arrangement would allow for a flexible 1 1/4-in. discharge hose. To meet code requirements, however, we needed to upgrade to 1 1/2-in. rigid PVC pipe. And because check valves need occasional cleaning, we opted to move the check valve outside the box and make our size conversion there.

To extend the smaller piping, thread the 1 1/4-in. coupling onto the pump outlet with Teflon tape. Then, install a 6-in.-long x 1 1/4-in. threaded nipple into the coupling, again using Teflon tape, and set the pump into the sump box.

Because the sump box needs to be sealed to check the flow of sewer gases, it comes equipped with a foam rubber gasket. Just peel the paper from the adhesive side and stick it to the top of the box, next to the fastening nuts. Then, place the lid onto the gasket and tighten it down with the bolts provided in the kit. Finish by sliding the neoprene donut gasket over the pump riser pipe and seating it in the box lid. At this point, install the gasket that seals in the electrical cords.

With the pump installed in the box, thread a second 1 1/4-in. coupling onto the pump riser pipe and thread the check valve into the coupling, again using Teflon tape on the threads. Then, to make the size conversion, slip a 1 1/4-in. x 1 1/2-in. banded coupling over the barbed end of the check valve and tighten the clamp. Follow this with two short stubs of pipe and two 45° elbows to move the discharge riser back to the wall. From the remaining opening in the box lid, use a similar arrangement to bring the vent pipe up from the box and back to the wall. Note the lid gasket for the vent opening is sized to the hub of the fitting. Finish up the sink-to-sump assembly by trimming the sink's tailpiece to length and joining it to the sump box with a 1 1/2-in. trap.

Existing Pipe Connections

The trickiest part of running the remainder of the piping is identifying an existing vent that you can tap. Vents can take many forms, but to the uninitiated, they generally have the look of pipes that don't do anything. In the case of a basement bath or any other secondary stack in the basement, the vent is the piping that extends upward from the drain tee of the fixture. Where no basement drains are present, a vent for upstairs fixtures will often take off just below the toilet tee on a full-sized stack and disappear into an upstairs wall. Expect these vents to be 1 1/2 to 2 in. in diameter.

In our case, we tapped the vent serving a first-floor bath that was located next to the primary stack. While the location for each vent may be different, the connections won't vary much. As far as making the cuts is concerned, a hacksaw will cut plastic, copper and galvanized iron. And when it comes to connections, all can be made to code with banded couplings.

With the sump's drain and vent risers brought up to ceiling height, run both to the existing piping you want to tap for the final connections. Keep in mind that once the risers go horizontal, across the basement ceiling, you'll need to establish conventional flow rates. Shoot for something between 1/8 in. and 1/4 in. per ft. of downward slope for the drain line and a slight upward slope for the vent line.

To make the vent stack connection, begin by cutting out a section of the stack large enough to accept a tee fitting. Because a vent's flow is always upward, install the tee upside down. With the tap made, simply glue the vent pipe from the sump into the branch of the tee.

To tap into a plastic drain stack, glue short stubs of pipe into a 3-in. wye and hold the wye against the stack as a marking guide. Mark the section to be removed and cut through the stack twice with a hacksaw. Then, splice the wye into the stack with 3-in. banded couplings. Tighten the couplings in place with a nut driver and run pipe and fittings up to join the drain line.

Cutting into waterlines is a good deal less complicated because there are fewer code considerations and hot and cold waterlines are easy to identify. Begin the installation by shutting off the water and draining the system by opening all upper and lower fixture faucets. Then, cut into the existing hot and cold waterlines with a tubing cutter. Splice in copper sweat tees and join the new lines to the tees with 90° copper elbows. Be sure to use non-acid flux and leadfree solder on all joints.

Step-by-Step Illustrations

  1. Slide the faucet base into the sink holes and thread jamb nuts over the faucet shanks. Firmly tighten the nuts.
  2. Attach a flanged tailpiece to the drain fitting. Use a nylon insert washer or a flat rubber washer to make the seal.
  3. Attach a copper ball-head supply tube to each faucet shank with a nut. Tighten each two turns past finger-tight.
  4. Cut two 1/2-in. copper risers to length. Then solder a drop-eared elbow to each. Use flux and lead free solder.
  5. Thread a close nipple into each shutoff valve then into both drop-eared elbows. Use Teflon tape on the threads.
  6. Attach leg brackets to the floor, then place sink legs over the brackets. Join the two with screws and nuts.
  7. Slide a compression nut and ferrule onto both supply tubes. Then, tighten the nuts with an adjustable wrench.
  8. Start installing the sump box by threading a 1 1/2-in. male adapter into the drain opening on top of the box.
  9. Glue pipe nipples and 45° elbows together to align the waste opening on the box to the sink tailpiece.
  10. Install a coupling and riser nipple to the top of the pump using Teflon tape. Then, lower the pump into the box.
  11. Install the supplied gasket around the top of the box, then cover it with the lid. Tighten the lid in place with bolts.
  12. Attach a check valve to the discharge riser, then a banded increaser coupling over the top of the check valve.
  13. Use pipe nipples and 45° elbows to angle the discharge riser (left) and the vent (right) back to the wall.
  14. Install a 1 1/2-in. trap between the sink tailpiece and the waste line into the sump box. Tighten all nuts securely.
  15. Find a proper vent pipe, then glue an inverted tee into this line. Glue the sump vent into the tee's branch fitting.
  16. Glue a pipe nipple into each end of the wye fitting. Then, hold this assembly against the stack and mark both ends.
  17. Cut out a section of the stack, then slide the wye assembly into place. Secure with two banded couplings.
  18. Connect the drainpipe from the sump to the wye fitting in the stack, using glue, pipe nipples and elbows.
  19. Cut both supply lines and solder a 3/4 x 1/2 in. tee into each. Then solder the tees to the sink supply lines.

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