| In
This Article:
Very lousy sink drain pipes
literally fall off and are replaced with a proper slip-joint
fittings, P-trap and flexible coupling. An air admittance
valve is added for proper venting. |
Related
Articles:
|
| Skill Level:
3 (Intermediate) |
Time Taken:
About 3 Hours |
By
Bruce W. Maki,
Editor
One evening my neighbor told me about a plumbing problem he was
experiencing. The kitchen sink in their 110-year-old house was
backed up. His wife was using a plunger on the sink drain when
suddenly the drain pipe fell off, dumping dirty water all
over the kitchen floor.
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The drain plumbing looked like this before
it broke apart.
The whole arrangement of drain piping was done
poorly. For a start, flexible drain pipes just don't
work very well.
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| The section between the two red arrows had
fallen off from the agitation of plunging the
plugged-up sink. |
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| The kitchen sink was actually straddling
two separate base cabinets, so the drain to the left
basin went through a hole in the cabinet partition. This
wasn't a problem... it's just a bit unusual. |
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I began by taking apart the old drain
piping. |
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| The nut (lower arrow) was actually
cracked, and barely held the trap together. Somebody had
applied a heavy layer of pipe thread compound to this
connection.
Note that this entire S-trap was upside down.
The nut is normally on the top piece... but I'm not sure
it really matters. |
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This part of the trap had been merely
inserted into the end of the 1½" galvanized steel
pipe. Since the steel pipe had been cut off, and was not
threaded, the slip-joint nut didn't actually engage
anything.
Surprisingly, this connection didn't leak, even when
the drain was backed up. |
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| The proper approach is to use a flexible
rubber coupling, commonly called a "Fernco".
I used a small fine file to remove the burrs and
rough spots on the end of the steel pipe. I didn't want
to take chances with the rubber coupler leaking.
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Hack Job:
The drain plumbing had been installed without a
slip-joint nut on this fitting below the sink
tailpiece.
This connection didn't leak badly when the sink was
plugged, but water had been seeping out somewhere,
leaving these brown stains. |
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| After I removed the white plastic pipes I
tried to remove the metal nut (red arrow) on the bottom
of the sink basket.
I placed a basket wrench in the drain (from
above) and had the homeowner hold the wrench to keep the
basket from turning. Then I used a large pair of
Channel-Lock pliers to remove this metal nut. The
corrosion on the threads made it very difficult to
remove. |
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Despite our efforts, the basket rotated a bit. That was a
problem.
When the sink basket moves it almost always leaks. So I
had to remove the sink basket on both basins. Of course one of the
the large ring-nuts broke, so we had to buy another.
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After the baskets had been removed, I
cleaned up the sink. |
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| Note spots around the rim of hole. Even
rubbing alcohol wouldn't remove these spots, though I
could scrape them off with a screwdriver.
I figured these spots were hard water deposits, so I
applied some calcium and rust remover with a
stiff bristle brush, and then rinsed thoroughly with
water. This removed all of the spots. |
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Once the sink had been cleaned up, I installed the baskets.
Instead of using plumber's putty (which I think is actually a joke
product) I used clear silicone between the underside of the
basket and the sink. Read about installing
sink baskets in an earlier article.
 |
If I tried to attach anything to the
basket while the silicone was soft I would probably
squeeze out the caulking, creating a mess and possibly
inviting a leak.
After the silicone around the basket rim had cured
for an hour, I installed the tailpiece. I used a dab
of TFE pipe thread compound on the metal threads and
used pliers to tighten the metal nut. |
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Proper Drain Pipes:
| This is a sink drain kit, which we
got at Home Depot.
This set of pipes connects the two basins together
and directs the drain water towards the trap.
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After I installed the drain kit, I had two
pipe ends (arrows) that needed to be joined together.
But... I also needed a trap and an air admittance
valve between these two pipes. |
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| Since the end of the steel drain pipe was
rather rough, I applied a thin layer of pipe
thread compound and spread it around. |
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|
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I slipped the flexible coupling (a.k.a.
"Fernco") over the end of the pipe. |
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| Then I tightened the screw on the band
clamp.
The instructions say to tighten the band clamp screw
to 50 inch-pounds of torque. That's pretty firm. |
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The Final Section Of Drain Pipe:
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This is an air admittance valve,
which we bought at Home Depot for about $24. While this
part added to the cost of the repair, it also improved
the flow of the sink drain.
This air valve came in two parts, which need to be
screwed together hand tight only.
Note: There needs to be an inch or two of room
above the air valve, in case the top section needs to be
removed for maintenance or replacement. |
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| The basic P-trap kit. |
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The other important drain component is a tee fitting. There are
several types of tee fittings available. I used a sanitary tee
fitting (seen in the picture below) which has a curvature
to help direct drain water down into the vertical pipe.
With all the necessary pipe and fittings in my hands, I laid out
the drain line connection from the pipe below the sink to the old
steel pipe that poked up through the floor.
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Laying Out Pipe Fittings:
When figuring out the
layout of plumbing systems, I always do a "dry
fit" without glue before committing to
anything.
First I assembled the P-trap
(1 and 2) and installed them on the vertical drain pipe
(below the sink) making sure I had at least one inch
of overlap.
Then I established the
height of the sanitary tee fitting (3) which gave
me the length of the first section of 1½" pipe
(P1).
Next I determined the
distance of the slip-joint adapter (4) from the
tee fitting, giving me the length of the short lateral
pipe P2. I could have made piece P2 a couple of inches
longer... and just cut part #2 a bit shorter. |
The air vent (the
blue-striped part above #5) needed to be at least 4 inches
above the water level of the trap, so I cut pipe P3
accordingly. I placed the air vent connector hub (5) on top of
this pipe to make sure everything would fit below the sink
basin.
Warning About Dry Fitting:
When dry fitting PVC
pipe and fittings, the pipe won't slide into the
fitting's hub all the way. But when PVC cement is
applied the liquid acts like a lubricant and then the
pipe can easily slide all the way in. This fact means
that the entire assembly of pipe and fittings will be a
little shorter than the length of the dry-fit assembly.
It seems that during
dry fitting the pipe will enter the hub about 2/3 to 3/4
of the actual overlap amount. You can force the pipe in
farther but it will be difficult to remove.
I simply compensate by
making the dry-fit section of pipe a little bit longer
than the desired final length. With this size of pipe
I'd estimate that I add a quarter-inch per
pipe/hub connection. |
Also: It's important
to verify that the trap can be assembled and taken apart.
It's possible to glue up the drain pipe and then be unable to
get the slip-joint fittings into place because supply pipes or
cabinet walls are in the way (though most sink base cabinets
don't have this middle partition).
Since I was using a rubber coupling, which is removable,
these concerns did not apply.
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Read about cutting
PVC pipe...
Gluing The Pipe Together:
| Once I had cut the PVC pipe to the
required lengths and done a trial fit-up, I took the PVC
parts outside to glue together.
The PVC primer and pipe cement gives off some strong
vapors, so it's best to do the gluing where the
ventilation is good. |
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I applied some PVC primer to the inside of
each hub (female part of the fittings) and let it dry
for a minute or two. Then I applied primer to the ends
of the pipe, and after a brief drying time I glued
everything together.
For more information read Gluing
PVC Pipe and Fittings...
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| The completed drain assembly, ready to be
installed in the rubber coupling. |
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I pushed the drain assembly into the
rubber coupling and tightened the band clamp. |
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| Then I assembled the downstream portion of
the trap. (Red arrow)
First I inserted the straight section into the
slip-joint adapter (which goes directly into the
tee fitting). Then I aligned the curved part with the
J-shaped piece of the trap and connected the pieces
together with the slip-joint nut.. |
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After I made sure all the slip-joint nuts
were firmly hand-tightened, I was done.
Using a wrench or pliers on these plastic nuts is not
recommended.
To test for leaks, I filled each sink basin with
water and then pulled the drain stopper. I examined each
connection for signs of water, but everything was dry. |
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Now the water drains from kitchen sink much faster than before,
thanks to the air admittance valve.
More Info:
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Tools
Used:
- Channel-Lock
Pliers, 12", 18"
- Screwdriver,
Flat
- File,
Fine
- Miter
Saw (Optional)
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Materials
Used:
- 1½"
Sink Tailpieces (2)
- Kitchen
Sink Drain Kit, 1½"
- P-Trap,
1½"
- Slip-Joint
Adapter, 1½"
- Sanitary
Tee Fitting, 1½"
- Air
Admittance Valve
- 1½"
PVC Pipe
- 1½"
Flexible Rubber Coupling
(a.k.a. "Fernco")
- Pipe
Thread Compound
- Teflon
Pipe Tape
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