The Old Tradesman

The tips library

Drains, traps and cast iron

A drain has nothing but gravity on its side, so every joint on it has to be made right the first time. Here's how I set a trap washer, putty a strainer and cut and band cast iron, with the maker's sheet behind every number.

Tip 1

Point the bevel at the joint

The trick

The tapered side of a slip-joint washer faces the threaded fitting it seals into: the drain stub-out, the threaded end of the pipe, the trap bend.

Slip joint washer, right and wrong way Cut away of a trap slip joint. Right: the tapered side of the washer points into the mouth of the threaded fitting and the slip nut pushes it in. Wrong: the washer is turned around, so the flat face meets the flare and nothing wedges. SLIP JOINT, CUT AWAY Slip nut Fitting Tailpiece RIGHT: bevel points into the fitting. WRONG: flat face on the flare. No wedge.

Why. The taper is a wedge. The slip nut drives it into the mouth of the fitting and it spreads to seal. Turned around, there's nothing to wedge.

The tell. Trap weeping after you put it back together? Pull the nut and look at the washer before you reach for more wrench. A backwards washer leaks at any torque.

The Home Depot's guide says it three ways: bevel toward the threaded portion of the pipe, toward the drain stub-out, toward the trap bend. HomeTips puts it the same: the tapered side points toward the fitting being sealed.

When to stop. Trap arm won't line up with the wall stub without forcing it? Don't pull it in with the slip nuts. A piece is the wrong length, and that gets cut or replaced.

Sources

Tip 2

Plastic slip nuts: by hand, then a quarter turn at most

The trick

Tighten a plastic trap nut by hand. If it still needs it, give it one more quarter turn with slip-joint pliers. That is the whole allowance.

Why. The washer makes the seal, not the threads. Past snug, the force goes into the plastic nut and the soft washer, and HomeTips says too much force cracks plastic fittings or distorts washers.

The tell. Leak a week after you leaned on it? Look for a hairline crack in the nut. The Home Depot's guide says to make small movements so you don't overtighten.

When to stop. Cracked nut or a split trap? Replace the piece. More turns or tape will not hold a cracked plastic nut.

Sources

Tip 3

Roll the putty half an inch thick, and let it squeeze

The number

Knead it soft, roll a rope about 1/2 inch thick, lay a full ring under the flange and blend the two ends. Tighten to snug: some putty should squeeze out, not all of it.

Why. Putty fills the gap between the flange and the sink. Too thin leaves voids, and Oatey's guide says the goal is a snug fit, not crushed putty.

The tell. Look for an even ribbon of squeeze-out all the way around. A dry spot is a void. Roll a longer rope instead of stretching a short one thin.

Same goes inside a toilet tank. Fluidmaster's repair kit sheet says not to use plumber's putty to seal its fittings.

When to stop. Putty never goes on pipe threads or anything under water pressure, Oatey says, and its putty is not designed for ABS: it can degrade the plastic. ABS drain body means a different sealant.

Sources

Tip 4

Regular putty can stain a stone counter

The trick

Granite, marble, quartz or sandstone? Use stain-free putty, and never mix it with regular putty.

Regular putty can stain stone Top view of two sink strainers on a stone counter. The one set in regular oil based putty has a dark ring around it where oil wicked into the stone; the one set in stain-free putty is clean. Use stain-free putty on granite, marble, quartz and sandstone, never mixed with regular putty. STRAINER ON STONE, TOP VIEW Regular putty Stain-free putty Oil wicks into stone Granite, marble, quartz, sandstone: use stain-free putty, and never mix it with regular putty. Not for ABS either. Odd material? Test a hidden spot.

Why. Regular plumber's putty is oil based. Oatey says it may stain porous stone, and the oil is what leaves the dark ring around the drain.

The tell. A dark halo spreading out from a strainer on stone is regular putty's oil. Check the counter before you open the tub; Oatey's stain-free sheet says mixing the two grades can still stain.

Oatey's stain-free sheet lists granite, marble, quartz, sandstone and solid surface counters, and says to test an unusual material in a spot nobody will see first.

When to stop. Stain-free putty is not for ABS either, per the same sheet. ABS drain body: a different sealant.

Sources

Tip 5

Score it, turn it, then snap it

The trick

Squeeze the snap cutter only enough to mark the pipe. Release, turn the tool a few degrees, score again. Then one quick, hard squeeze to break it.

Snap cutter: score, turn, snap Three end views of cast iron pipe inside a chain snap cutter. One: squeeze just enough to mark the pipe. Two: release, turn the tool a few degrees and score again. Three: one quick, hard squeeze snaps it along the score line. SNAP CUTTER ON CAST IRON, END VIEW 1. SCORE Squeeze just enough to mark the pipe. 2. RELEASE, TURN a few degrees, score again. 3. SNAP One quick, hard squeeze. Max wheels on the pipe.

Why. Cast iron breaks along the line you give it. A score all the way around tells the break where to run; full pressure on the first pass doesn't.

The tell. Ragged break? Look at the chain. Get as many wheels on the pipe as you can, and every wheel sharp and turning. Tyler says dull, flattened wheels make a good cut very difficult, if not impossible.

Tyler's sheet: on an unusually tough piece, score it several times. RIDGID's manual says the same: mark it, loosen, rotate, mark again all the way around, then tighten and break. Turn the chain end for end now and then so all the wheels wear evenly (AB&I and Tyler).

When to stop. A stack carrying pipe above the cut is a plumber's cut. See the next tip before anybody touches the chain.

Sources

Tip 6

Strap the stack before you cut it

The number

Before a section comes out, tie the stack in place: wire or strap wrapped around the pipe above the cut, just under a hub or an elbow, each end fastened to a joist or header. Make the cut 4 inches or more from any hub or joint.

Why. Cast iron is heavy, and once it's cut the pipe above hangs on whatever you tied. The hub gives the strap a shoulder to catch so the pipe can't slip down.

The tell. The strap should sit tight under the hub with no slack. If you can slide it, the pipe can drop. RIDGID warns cut pieces can be thrown with considerable force, and says to restrain short sections too.

When to stop. Charlotte Pipe says cast iron installation belongs to a licensed plumbing contractor. A stack carrying pipe above you is where I take that literally.

Sources

Tip 7

Square cut, then both ends to the center stop

The number

Cut square; Mission's sheet says the ends must be smooth and square. Push each pipe end into the gasket until it hits the molded center stop, then slide the band assembly over and center it on the gasket. Separately, Charlotte allows no more than 5 degrees of deflection at any joint.

Why. The stop splits the gasket between the two pipes, so each band clamps the same length of rubber over pipe. A short or angled end leaves one side clamping less.

The tell. Shield sitting off center, or the gasket bulging on one side, means one pipe never reached the stop.

When to stop. Chipped end, or a cut you can rock a straightedge on? Cut it again. The gasket won't make up for it.

Sources

Tip 8

Sixty inch-pounds on a torque wrench, not on feel

The number

Standard no-hub bands, 1-1/2 to 10 inch: 60 in-lb on a calibrated torque wrench. Heavy and medium duty (Fernco, 1-1/2 to 10 inch): 80. On 12 and 15 inch the sheets split, Anaco 80 and Fernco 120, so the sheet with your coupling wins.

No-hub coupling band order and torque Side view of a four band no-hub coupling over two pipes butted at the center stop. Snug the two inner bands by hand, then the two outer bands, then tighten alternately to 60 inch-pounds. Standard couplings 1-1/2 to 10 inch take 60 inch-pounds, heavy and medium duty 80; on 12 and 15 inch the makers differ, so follow the coupling sheet. NO-HUB COUPLING, FOUR BANDS Both pipes butt the center stop 1 2 3 4 Step 1: snug 2 and 3 by hand. Step 2: snug 1 and 4 by hand. Step 3: alternate to 60 in-lb. Standard, 1-1/2 to 10 in: 60 in-lb Heavy and medium duty: 80 in-lb 12 and 15 in: the sheets split. The coupling sheet wins.

Why. The bands have to squeeze the gasket enough to seal without crushing it. A preset wrench gives the same number on every screw; a nut driver and your wrist don't.

The tell. On a four-band coupling, Mission snugs the two inner bands by hand, then the outer two, then tightens them alternately to 60. Running one band all the way down first is the mistake.

Anaco: on 5 to 10 inch couplings, inner bands first, then outer, alternating the screws; on 12 and 15 inch, inner, center, then outer. Two-band couplings just get tightened alternately.

When to stop. No sheet, and you can't tell which coupling it is? Then you don't know if it's 60, 80 or 120. Get the sheet before you get the wrench.

Sources

Tip 9

Size a rubber transition coupling by outside diameter

The number

Fernco sizes its flexible couplings by outside diameter, not nominal size. Measure the OD of both pipes, soap the pipe (not the coupling), and tighten standard clamps to 60 in-lb.

Why. Same nominal size doesn't mean the same outside diameter, and the rubber seals on the outside. Soap on the pipe lets it slide in; Fernco says soaping the coupling makes it hard to grip.

The tell. A coupling clamped extra hard to stop a weep is usually the wrong size for one of the pipes.

Burying one? Fernco rates its standard couplings for below ground but recommends a shielded coupling there, and says to pressure test before backfilling or covering the joint. Confirm it against your local plumbing code.

When to stop. These are for gravity drain, waste and vent only. Fernco says they are not rated for pressurized water lines. Never on a supply.

Sources

The Old Tradesman is a cartoon character. Every tip on this page stands on the sources listed under it. He is the voice. They are the authority. The drawings are diagrams, not photographs.

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