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Renovation 4th Edition

Page 78

by Michael Litchfield

they are also invaluable to renovators.

  fitting or replacement pipe section, unroll the

  2-in. copper vent pipe, and a 2-in.

  For example, if you want to add a plastic

  cast-iron takeoff on a 2 by 3 wye

  neoprene sleeves onto the fitting or pipe, and

  shower drain to a cast-iron stack, no-hub cou-

  fitting. The other couplings join 3-in. tighten the steel band clamps. You can also tie

  plings can accept either a cast-iron or a plastic

  no-hub cast-iron fittings.

  into a cast-iron drain without cutting into it by

  no-hub fitting and seal it tightly to the pipe

  building out from an existing cleanout, as shown

  ends once you’ve cut into the stack. (support

  in “Extending a Cast-Iron Main Drain” on p. 340.

  P R O T I P

  both sides of the section to be cut out so it can’t

  Venting Options

  shift during cutting and weaken other joints.)

  When joining dWV pipes of different materi-

  If you smear liquid soap on

  Until you expose the framing and actually run

  als, use specialized transition couplings whose

  the outside of cast-iron pipes

  the pipe, it’s difficult to know exactly how things

  and no-hub fittings, you’ll have

  neoprene sleeves are sized for incoming pipes

  will fit together—especially vents. Because cor-

  an easier time pulling the neo-

  with different outside diameters, such as the

  rect venting is crucial, this section discusses sev-

  prene sleeves onto them.

  coupling used to join 2-in. copper and 2-in. cast

  eral venting options. But first, here are a few

  iron, shown in the bottom photo at left.

  terms to keep straight: A stack is a vertical pipe.

  If the stack carries wastes, it’s a soil stack. If the

  334 Chapter 12

  side of a drainpipe: If it did, it could become

  clogged with waste.

  maximum Distance:

  Branch vents must rise to a height of at least

  Trap arm to vent* 42 in. above the floor before beginning their hori-

  zontal run to the vent stack. This measurement

  TRaP aRm

  maXImum dIsTaNce

  adds a safety margin of 6 in. above the height of

  dIameTeR (in.)

  To VeNT

  the highest fixture (such as a sink set at 36 in.),

  so there is no danger of waste flowing into the

  11⁄4

  

  2 ft. 6 in.

  vent. Since branch vents run to a vent stack, they

  11⁄2

  

  3 ft. 6 in.

  should maintain an upward pitch of at least 1⁄4 in.

  per ft., although the UPC allows a vent to be level

  2

  

  5 ft.

  if it is 6 in. above the flood rim of a fixture.

  3

  

  6 ft.

  sTaCk venTIng

  4

  

  10 ft.

  Clustering plumbing fixtures around a central

  * Also maximum distance of stack-vented fixture trap arm

  stack is probably the oldest method of venting. In

  to stack, based on calculations found in the UPC, T10-1.

  the early days of indoor plumbing, plumbers

  noticed that fixtures near the stack retained

  water in their traps while those (unvented) that

  were at a distance did not. You can vent three

  bathroom fixtures (lavatory, tub, and toilet) off a

  3-in. stack vent, without additional branch

  zzzzzz Back venting

  (Continuous venting)

  vents—if you detail it correctly, as shown in

  “Stack Venting” on p. 336.

  3-in.

  Note: When stack venting, never place a toilet

  stack vent

  above the other fixtures on the stack: Its greater

  discharge could break the water seals in the traps

  of small-dimension pipes. If you must add fix-

  tures below those already stack vented, add (or

  11/2-in.

  2-in.

  extend) vent stacks and branch vents. The maxi-

  branch vent

  vent stack

  mum allowable distance from stack-vented fix-

  tures to the soil stack depends on the size of the

  minimum Drain, Trap, and vent sizes

  2-in.

  branch vent

  3-in.

  FIXTuRe/aPPLIaNce

  dRaIN/TRaP sIze

  VeNT sIze

  soil stack

  Toilet

  

  3 in. or 4 in.

  2 in.

  Bathtub/shower

  

  2-in. drain; 11⁄2-in. trap

  11⁄2 in.

  shower stall

  

  2 in.

  11⁄2 in.

  Lavatory

  

  11⁄2-in. drain; 11⁄4-in. trap

  11⁄4 in.

  3-in.

  Paired lavatories

  

  2-in. drain; 11⁄2-in. trap

  11⁄2 in.

  main drain

  Bidet

  

  11⁄4 in.

  11⁄4 in.

  kitchen sink (with or without disposer)  11⁄2 in.

  11⁄2 in.

  dishwasher

  

  11⁄2 in.

  11⁄2 in.

  In this illustration of back venting, all

  fixtures have a dry branch vent—that is,

  Laundry tub

  

  11⁄2 in. or 2 in.

  11⁄2 in.

  no vent ever carries water. The fixtures

  clothes washer standpipe

  on the first floor require a 2-in. branch

  

  2 in.

  11⁄2 in.

  vent because the toilet’s 3-in. drain

  

  needs more incoming air to equalize its

  large waste flow.

  plumbing

  335

  pipe serving a particular fixture (see “Maximum

  Distance: Trap Arm to Vent” on p. 335).

  zzzzzz stack venting

  venTIng ToIleTs

  3-in. stack

  3x11/2

  sanitary tee

  Because they have the biggest drain and vent

 

  11/2-in.

  p

  CONSTRICTED SPACES ipes of any fixture, toilets can be the trickiest to

  lav. drain

  When a branch dr v

  ai enn t

  m . uW

  st htreanv esl ptahcre

  o ubgehn

  ae a

  fl toho ra ptloatilfeotr ims bneofto rae prero ac bh-ing a stack, the drain must slope gradually.

  Here, the angle the vent takes off from the toilet drain is critical—it must not be less than 45 degrees, as depicted lem, use a setup such as the one show

  in the accompanying cross-section drawing. . n below

  in “Venting a Toilet,” in which a 2-in. vent pipe

  Closet flange

  43 closet bend

  rises vertically from a 3 by 2 combo, while the

  3-in. toilet drain

  3-in. drain continues on to the house main. The

  32 combo

  3-in.-dia. toilet drain allows the vent to be as far

  Min. 45 degrees

  2-in. vent

  as 6 ft. from the fixture, as indicated in the table

  on p
. 335.

  11/2-in.

  tub drain

  When space is tight, say, on a second-floor

  bathroom with finished ceilings below, the drain

  and vent pipes must descend less abruptly (see

  Side-inlet tee

  3-in. toilet drain

  “Constricted Spaces” below). Here, the critical

  4x3 closet bend

  detail is the angle at which the vent leaves the

  3 by 2 combo: That vent takeoff must be 45° above

  a horizontal cross section of the toilet drain. If it

  If close enough to a stack vent of adequate size, fixtures can

  is less than that, the outlet might clog with waste

  use it for venting (see “Maximum Distance: Trap Arm to Vent” on p. 335).

  and no longer function as a vent. As important,

  Note: The side inlet serving the tub enters above the toilet inlet;

  the “horizontal” section of the vent that runs

  this fixture group must be the highest on the stack.

  between the takeoff and the stack must maintain

  a minimum upward pitch of 1⁄4 in. per ft.

  2-in. vent

  zzzzzz venting a Toilet

  zzzzzz Constricted spaces

  2-in. vent

  Closet flange

  Closet flange

  Minimum upslope of

  1/4 in. per ft.

  45° minimum

  4x3 closet bend

  4x3

  3x2 low-heel vent or

  closet bend

  3-in. tee with 2-in.

  bushing

  3-in. toilet drain

  3x2 combo

  3-in. drain

  3-in. combo

  When a branch drain must travel through a

  floor platform before reaching a stack, the

  drain must slope gradually. Here, the angle

  the vent takes off from the toilet drain is

  When there’s plenty of space under a

  critical—it must not be less than 45°, as

  toilet—say, in an unfinished basement—

  depicted in the cross-section drawing

  the branch drain can descend steeply.

  on the facing page.

  336 Chapter 12

  When you’ve got two toilets back to back, you

  In addition to the fittings shown in the draw-

  can save some space by picking up both with a

  ing, note these factors as well: The loop must rise

  single figure-5 fitting (double combo), like the

  as high under the counter as possible and at least

  small one in the bottom right photo on p. 333.

  6 in. above the juncture of the trap arm and the

  From the top of the fitting, send up a 2-in. or

  sanitary tee to preclude any siphoning of waste-

  3-in. vent; from the two side sockets use two 3-in. water from the sink. The vent portions may be

  soil pipes serving the toilets; and use a long-sweep 11⁄2-in. pipe, but the drain sections must be 2 in.

  ell (or a combo) on the bottom to send waste on

  in diameter, and drain sections must slope down-

  to the main drain. This fitting is about the only

  ward at least 1⁄4 in. per ft.

  way to situate back-to-back water closets and is

  air-admittance valves (aaV) are one-way

  quite handy when adding a half bath that shares

  mechanical vents designed to eliminate the need

  a wall with an existing bathroom.

  for conventional branch vents for fixtures too far

  from a wall. As water drains from a sink, it cre-

  oTher venTIng opTIons

  ates a partial vacuum within the pipes, depress-

  ing a spring inside the AAV and sucking air in.

  Common vents are appropriate where fixtures

  When the water is almost gone and the vacuum

  are side by side or back to back. This type of vent is equalized, the spring extends and pushes its

  usually requires a figure-5 fitting.

  diaphragm up, sealing off outside air once again

  Loop vents are commonly installed beneath an

  and preventing the release of sewer gases.

  island counter in the middle of a room. The sink

  Because fixture drains with AAVs don’t need lat-

  drain is concealed easily enough in the floor plat-

  eral vent runs or additional vent-stack penetra-

  form, but the branch vent, lacking a nearby wall

  tions in the roof, they allow greater design flexi-

  through which it can exit, requires some ingenu-

  bility, while saving considerably on labor and

  ity. This problem is solved by the loop shown in

  materials. Mechanical vents were once intended

  “Venting an Island Sink” below.

  Branch

  zzzzzz vent-Takeoff Cross section

  vent

  zzzzzz venting an Island sink

  Countertop

  Wall

  Section of

  (flood rim)

  horizontal drain

  90° ell

  45° ell

  OK

  11/2 in.

  2 in.

  Cleanout

  P-trap

  OK

  45° minimum

  Long-sweep

  Sanitary tee

  ell

  Floor

  Combo

  11/2-in.

  Cleanout

  foot vent

  No!

  Combo

  2-in. branch drain

  Wastes

  A looped vent is one code-approved way to vent an island sink.

  The loop should extend as high as possible under the countertop.

  Vents must take off from horizontal

  Loop preassembly makes construction easier. The foot vent must

  drains at a 45° angle minimum. If the

  connect to the loop via a combo fitting and slope upward to the

  takeoff angle is less than 45°, wastes

  stack at a minimum of 1/8 in. per ft.

  can block the vent.

  plumbing

  337

  to be only temporary, but their valve mechanisms

  have been improved so that air-admittance valves

  gOiNg WiTH THe Flow

  are now accepted by major building codes,

  To optimize flow and minimize clogged pipes,

  including the IRC.

  follow these guidelines:

  

  venT TermInaTIon

  dRaINage FITTINgs. use a long-sweep ell

  (90° elbow) or a combo when making a 90°

  To reduce chances that vent gases will enter the

  bend on horizontal runs of waste and soil pipe

  home, stack tops must be at least 6 in. above the

  and where vertical pipes empty into horizontal

  upslope side of the roof and at least 3 ft. above

  ones. use a standard ell when going from

  any part of a skylight or window that can be

  horizontal to vertical. Where trap arms join vent

  opened. A vent stack must be at least 12 in. hori-

  P R O T I P

  stacks, use sanitary tees. (Long-sweep fittings

  zontally from a parapet wall, dormer sidewalls,

  and the like. Finally, stacks must be correctly

  are not required on turns in vent pipe; regular

  when ordering supplies,

  flashed to prevent roof leaks.

  tees and ells may be used there.)

  order 20% more pipe than you

  think you’ll need and at least

   cLeaNouTs. cleanouts are required where a

  a half-dozen extra of the more

  buildi
ng main joins a lead pipe from a city sewer

  Roughing-in DWV Pipes

  common fittings such as tees,

  line or septic tank, at the base of soil stacks,

  In new construction, pros typically start the DWV

  combos, ells, and couplings.

  and at each horizontal change of direction of

  system by connecting to the sewer lead pipe, sup-

  you’ll also need straps and

  45° or more. also, install cleanouts whenever

  porting the main drain assembly every 4 ft. and

  clamps to support pipe runs,

  at each point a fitting is added.

  as well as consumables such as

  heavy flow increases the possibility of clogging,

  Renovation plumbing is a different matter

  solder or plastic-pipe cement and

  such as in back-to-back toilets. There must be

  altogether, unless an existing main is so corroded

  plumber’s sand cloth. most supply

  enough room around the cleanout to operate a

  or undersize that you need to tear it out and

  stores accept returns, but check

  power auger or similar equipment.

  their policy before ordering.

  replace it. Rather, renovation plumbing usually

  entails tying into an existing stack or drain in the

  most cost- and time-effective manner. There are

  three plausible scenarios: (1) cutting into a stack

  to add a branch drain, (2) building out from the

  end of the main drain where it meets the base of

  pipe-support spacing the soil stack, and (3) cutting into the main drain

  in midrun and adding fittings for incoming

  PIPe maTeRIaL

  HoRIzoNTaL suPPoRTs

  VeRTIcaL suPPoRTs

  branch drains.

  This discussion assumes that the existing

  Water supply

  pipes are cast iron and that new DWV pipes or

  copper

  

  6 ft.

  10 ft.

  fittings are ABS or PVC plastic, unless otherwise

  noted. If you’re adding several fixtures, position

  cPVc

  

  3 ft.

  10 ft. and midstory guide

  the new branch drain so that individual drains

  PeX

  

  32 in.

  Base and midstory guide

  can be attached economically—that is, using the

  least amount of pipe and fewest fittings.

  dWV

  Remember, drainpipes must have a minimum

  downward slope of 1⁄4 in. per ft.

  4 ft. and at

  10 ft. and midstory guides

  aBs or PVc

  

  branch connections

  if pipe ≤ 2 in.

  cast iron

  

  5 ft.

  Base and each story; 15 ft.

  When splicing a branch to an existing

  drain, support both sides of the

  takeoff fitting. Here, J-clamps are on

  both sides of a combo fitting.

  Transition couplings join copper to

 

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