Chris rondestvedt
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Hi,
Remodeling a master bath by adding a whirlpool tub. I'd appreciate feedback/clarification re horizontal wet vent vs standard ventining per Virginia plumbing code via the following questions. The attached diagram is keyed to the questions.
Your perspective will be much appreciated!
Chris
Horizontal wet vent vs standard vent clarification
1. Q: As shown the bathroom remodel plumbing concept picture is this a horizontal “wet vent” configuration with tub and shower sharing a drain and vented by the toilet stack/vent as shown?
a.Q: In this case is the tub trap arm 18 inches to the horizontal wet vent?
Virginia Plumbing Code:
Table 709.1 Drainage fixture units tub load factor 2 shower 2; minimum trap each 1.5 inch
Table 709.2 Fixture unit value for 1.5 inch trap tub 2 shower 2; for 2 inch trap tub 3 shower 3
Table 710.1 (1) Maximum drainage fixture units for 2 inch pipe at ¼ inch per foot 21
Table 710.1(2) Horizontal fixture branches for 2 inch pipe
-Max number drainage fixture units for horizontal branch 6 units
- Max number drainage fixture units: Total discharge units into one branch interval 6
909 Wet Venting
909.1 Horizontal wet venting permitted. Any combination of fixtures within two bathroom groups located on the same level is permitted to be vented by a horizontal wet vent
2. Q: If not a wet vent, is the configuration showing an approximately 7.5 foot ft tub trap arm (8 ft trap arm allowed by Virginia Plumbing Code table 906.1) to the vent with shower joining the trap arm acceptable?
908 common vent
908.1 Individual vent as common vent. An individual vent is permitted to vent two traps or trapped fixtures…located on the same floor level
908.2 Connection at same level. Where the fixture drains being common vented connect at the same level the vent connection shall be at the interconnection of the fixture drains or downstream of the connection
3. Q: If not acceptable would a separate vent of the shower p trap make the configuration acceptable?
4. Q: Would changing the piping and fittings from the toilet stack/vent up to and including the combo wye from 2 inch to 3 inch alter the tub trap arm calculation?
From 906.2 my understanding is that trap arm length is determined by pipe slope and pipe diameter as expressed in table 906.1 for 2 inch pipe at ¼ in per foot maximum trap arm is 8 feet though for 3 inch pipe at 1/8 inch per foot trap arm is limited to 12 feet.
Remodeling a master bath by adding a whirlpool tub. I'd appreciate feedback/clarification re horizontal wet vent vs standard ventining per Virginia plumbing code via the following questions. The attached diagram is keyed to the questions.
Your perspective will be much appreciated!
Chris
Horizontal wet vent vs standard vent clarification
1. Q: As shown the bathroom remodel plumbing concept picture is this a horizontal “wet vent” configuration with tub and shower sharing a drain and vented by the toilet stack/vent as shown?
a.Q: In this case is the tub trap arm 18 inches to the horizontal wet vent?
Virginia Plumbing Code:
Table 709.1 Drainage fixture units tub load factor 2 shower 2; minimum trap each 1.5 inch
Table 709.2 Fixture unit value for 1.5 inch trap tub 2 shower 2; for 2 inch trap tub 3 shower 3
Table 710.1 (1) Maximum drainage fixture units for 2 inch pipe at ¼ inch per foot 21
Table 710.1(2) Horizontal fixture branches for 2 inch pipe
-Max number drainage fixture units for horizontal branch 6 units
- Max number drainage fixture units: Total discharge units into one branch interval 6
909 Wet Venting
909.1 Horizontal wet venting permitted. Any combination of fixtures within two bathroom groups located on the same level is permitted to be vented by a horizontal wet vent
2. Q: If not a wet vent, is the configuration showing an approximately 7.5 foot ft tub trap arm (8 ft trap arm allowed by Virginia Plumbing Code table 906.1) to the vent with shower joining the trap arm acceptable?
908 common vent
908.1 Individual vent as common vent. An individual vent is permitted to vent two traps or trapped fixtures…located on the same floor level
908.2 Connection at same level. Where the fixture drains being common vented connect at the same level the vent connection shall be at the interconnection of the fixture drains or downstream of the connection
3. Q: If not acceptable would a separate vent of the shower p trap make the configuration acceptable?
4. Q: Would changing the piping and fittings from the toilet stack/vent up to and including the combo wye from 2 inch to 3 inch alter the tub trap arm calculation?
From 906.2 my understanding is that trap arm length is determined by pipe slope and pipe diameter as expressed in table 906.1 for 2 inch pipe at ¼ in per foot maximum trap arm is 8 feet though for 3 inch pipe at 1/8 inch per foot trap arm is limited to 12 feet.
