248 CMR, § 10.15

Current through Register 1537, December 20, 2024

Section 10.15 - Sanitary Drainage System

(1)Materials. Pipe, tubing, fittings, and traps to be used on any part of the sanitary drainage system in a building or adjacent to a building shall comply with all relevant sections of 248 CMR 3.00 through 10.00.

(2)Determining Size of Drainage System.

(a)Fixture Units for Drainage Piping. The waste discharge calculations for the drainage system piping shall be computed in terms of drainage fixture units in accordance with 248 CMR 10.15: Table 1: Fixture Unit Values for Various Plumbing Fixtures and 248 CMR 10.15(2)(b).

(b)Values for Continuous Flow. Fixture unit values for continuous or semi-continuous flow into a building sanitary drainage system, such as from a waste pump, sewage ejector pump, or similar device that discharges sewage waste shall be computed on the basis of two fixture units for each gallon per minute of flow. Exception: Installation of ejector pumps installed in compliance with 10.15(9): Table 5 with a maximum of 20 GPM.

(3)Selecting the Size of Drainage Piping. Pipe sizes shall be determined from 248 CMR 10.15(7): Table 1, 2 and 3 based on drainage fixture unit values calculated from 248 CMR 10.15(7): Table 1: Fixture Unit Valves for Various Plumbing Fixtures and 248 CMR 10.15(2)(b).

(4)Minimum Size of Soil and Waste Stacks. No soil or waste stack shall be smaller than the largest horizontal waste branch connected thereto, (See248 CMR 10.15(7): Table 1: Fixture Unit Values for Various Plumbing Fixtures and 248 CMR 10.15(7): Table 3: Maximum Loads in Fixture Units for Any One Branch Interval on Multistory Soil and Waste Stacks).

(5)Provision for the Installation of Future Fixtures. When future drainage provisions are considered regarding the potential installation of other fixtures, the drains provided shall be considered in determining the final required sizes of drains and vent pipes.

(6)Size of Underground Drainage Piping.

(a)Underground or Basement Floor. No portion of the drainage system installed underground shall be less than two inches in diameter.

(b)Sanitary Piping Installed Through the Foundation Wall.

1. Sanitary piping that pass through an exterior foundation wall shall be no less than four inches in diameter,

Exceptions:

a. When serving a Hazardous Waste System installed in accordance with (248 CMR 10.13).

b. When serving a residential laundry drain is conducted to a separate (Local Board of Health Authorized) dry-well disposal system. The minimum size drain shall be two inches in diameter.

c. When serving as a waste for baptistries or similar type fixtures, the drain shall be a minimum of two inches in diameter. See248 CMR 10.10(11).

d. When serving exclusively as the discharge from a semi-positive displacement grinder pump, and if so, the following shall be satisfied:

i. The minimum pipe size for a semi-positive displacement grinder pump discharge shall be HA-inch and shall provide a self-cleaning velocity of no less than two feet per second.

ii. The velocity in the pipe shall not be more than seven feet per second.

iii. A full port discharge valve and check valve shall be provided and made accessible inside the building.

iv. The waste discharge from semi-positive displacement grinder pumps shall be protected from freezing when the piping is installed less than four feet below grade in outside locations.

(i) The discharge shall be installed in accordance with the manufacturer's installation instructions:

(ii) shall be a minimum of 11/2 inch; and

(iii) an accessible check valve and full port shut off valve shall be installed on the discharge piping, and the discharge shall be properly protected from freezing.

e. Secondary structures and cabanas located on residential properties which discharge into the sanitary drainage system or building sewer of the main structure. Piping shall be sized in accordance with 248 CMR 10.15 but in no case less than two inches in diameter.

Table 1

Fixture Unit Values for Various Plumbing Fixtures

Type of fixture or group of fixtures	Fixture Unit Value
Bathtub or Tub & Shower Unit	2
Bidet	2
Dental chair unit or cuspidor	1
Dental lavatory	1
Drinking fountain/Water Station	1
Dishwasher, commercial	6
Dishwasher, Residential	1
Floor/trench drain 2-inch	4
Floor/trench drain 3-inch	5
Floor/trench drain 4-inch	6
Kitchen sink Residential (with or without disposer)	2
Lavatory with 1-1/4" outlet	1
Laundry Connection Residential	3
Laundry/Utility Sink	2
Shower stall Residential	2
Showers (group) per head	2
Sinks:
Surgeons	3
Flushing rim (with valve)	6
Service Sink with Trap Standard	3
Service Sink with P-Trap	2
Commercial Pot, scullery, etc. (each section) See Note 1 Below	4
Shampoo	2
Toilet, Tank Type	4
Toilet, Valve Operated	6
Urinal, pedestal, siphon jet blowout	6
Urinal, wall lip	4
Urinal, Waterless	1
Wash sink (circular or multiple) each 20 inches of usable length	1
Sizes for fixtures not listed above:
UA inch or less	1
11/4 inches	2
2 inches	3
21/2 inches	4
3 inches	5
4 inches	6

Note 1: See248 CMR 10.15(1)(b)2.d. for sizing using grease interceptors.

Note 2: See248 CMR 10.15(2)(b) for method of computing fixture unit values of devices with continuous or semi-continuous flows.

Note 3: The size of floor drains shall be determined by the area of the floor surface to be drained in accordance with 248 CMR 10.10(10)(a).

Table 2

Maximum Loads in Fixture Units for Horizontal Drains (F.U.)

Diameter of drain in inches	Horizontal Branch Drain (F.U.)	Building Drain
Diameter of drain in inches	Horizontal Branch Drain (F.U.)	1/8 in./ft. (F.U.)	1/4 in./ft. (F.U.)	1/2 in./ft. (F.U.)
11/2	3	---	---	---
2	6	---	---	---
21/2	12	---	---	---
3	34*	---	40*	48*
4	160	180	216	250
5	360	390	480	575
6	620	700	840	1,000
8	1,400	1,600	1,920	2,300
10	2,500	2,900	3,500	4,200
12	3,900	4,600	5,600	6,700
15	7,000	8,300	10,000	12,000

* Not more than four water closets

Table 3

Maximum Loads in Fixture Units for Soil and Waste Stacks Having One or Two Branch Intervals

Diameter of Stack (inches)	Maximum Load on Stack (F.U.)
11/2	4
2	8
21/2	20
3*	48
4	240
5	540
6	930
8	2,100
10	3,750
12	5,850
15	10,500

*No more than four water closets

Table 4

Maximum Loads in Fixture Units for Any One Branch Interval on Multistory Soil and Waste Stacks

The table is meant to be used for building with 15 or less branch intervals.

Please see formula and example below the table for buildings exceeding 15 branch intervals.

Diameter of Stack	Number of Branch Intervals													Maximum Total Load for Stack
3	4	5	6	7	8	9	10	11	12	13	14	15
2	3	----	----	----	----	----	----	----	----	----	----	----	----	10
2 1/2	8	7	----	----	----	----	----	----	----	----	----	----	----	28
3*	20	18	17	16	15	14	13	12	11	10	10	10	10	102
4	100	90	84	80	77	75	73	72	71	70	69	68	68	530
5	225	205	190	180	175	170	165	162	159	157	156	154	153	1,400
6	385	350	325	310	300	290	285	280	275	271	268	266	263	2,900
8	875	785	735	700	675	655	640	630	620	612	606	600	594	7,600
10	1,560	1,405	1,310	1,250	1,205	1,170	1,140	1,125	1,110	1,095	1,180	1,075	1,062	15,000
12	2,435	2,195	2,045	1,950	1,875	1,825	1,790	1,755	1,730	1,705	1,685	1,670	1,655	26,000
15	4,375	3,935	3,675	3,500	3,380	3,280	3,210	3,150	3,110	3,060	3,030	3,000	2,975	50,000

* No more than three water closets In buildings with three-inch stacks and more than fifteen branch intervals, no single branch interval shall exceed more than ten fixture units.

Formula to be used for buildings in excess of 15 branch intervals

N = The permissible load on a stack with one or two branch intervals as shown in Table 3

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n = Number of branch intervals on the stack to be sized

Example: Stack size = 4"

10 Branch Intervals Fixture Unit per Branch

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(7)Sizing of Offsets on Stacks and Vertical Drainage Piping

(a)Offsets of 450° or Less. An offset with a change of direction of 45 ° or less from the vertical, may be sized as a straight vertical stack. In the event a horizontal branch connects to the stack within two feet above or below the offset, a relief vent shall be installed in accordance with 248 CMR 10.16(2)(d). See 10.15: Example 1.

(b)Offsets of More than 45 °. A stack with an offset of more than 45 ° from the vertical shall be sized as a horizontal drain and as follows: See 10.15: Example 2

1. The portion of the stack above the offset shall be sized using 248 CMR 10.15: Table 3 based on the total number of fixture units above the offset.

2. The offset shall be sized using 248 CMR 10.15: Table 2.

3. The portion of the stack below the offset shall be sized based on the total number of fixture units on the entire stack above including the offset.

4. In buildings of five stories or more, a relief vent for the offset shall be installed as required elsewhere in 248 CMR 10.16(2)(d).

a. In no case shall a horizontal branch connect to the offset or to the stack within two feet above or below the offset.

10.15 Example 1 Offsets of 45° or less

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10.15 Example 2 Offsets of more than 45°

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(c)Offsets Above the Highest Branch. An offset above the highest horizontal branch is an offset in the stack-vent and shall be considered only as it affects the developed length of the vent.

(d)Offsets Below the Lowest Branch. In the case of an offset in a soil or waste stack below the lowest horizontal branch, there shall be no change in diameter required if the offset is made at an angle of less than 45°. If such an offset is made at an angle greater than 45 degrees to the vertical, the required diameter of the offset and the stack below it shall be determined using 248 CMR 10.15: Table 2.

(8)Drainage Piping Installations.

(a)See248 CMR 10.05 for the following:

1. Pitch of horizontal piping.

2. Fittings used to change direction.

3. Prohibited fittings.

4. Heel or side inlet bends.

5. Obstructions to flow.

(b)Back to Back Fixtures When Using a Single Fitting.

1.Horizontal: Shall by installed with the use of double sanitary wye fittings only to eliminate throw over.

2.Vertical: Shall be installed with the use of double sanitary drainage pattern tee fittings. See 10.15: Example 2.Exception: For water closets, double wye fittings may be used if required by the water closet manufacturer's installation instructions. See 10.15: Example 3.

Example 2 Double Sanitary Tee

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Example 3 Double Wye

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(c)Kitchen Sink Wastes (Residential).

1. Not less than a 11/2 inch branch waste or waste outlet shall be provided to receive the fixture drain from a kitchen sink, which shall connect independently to the sanitary drainage system.

2. A kitchen sink shall not waste into any horizontal drain smaller than three inches in diameter receiving discharge from a flat bottom fixture.

3. The roughed-in drain line for final connection to a kitchen sink shall be installed at a height to permit the installation of a food waste disposer.

4. A full-size cleanout shall be installed under all kitchen sinks.

Exception: A two-piece kitchen sink trap which may be disassembled for use in lieu of a clean-out.

(d)Laundries Drains in Multi-Story Buildings. In buildings where laundries are installed on more than three branch intervals, the waste line shall be connected to an independent laundry stack. See 10.15: Example 4.

1. The independent laundry stacks shall connect to an independent laundry main drain.

2. The independent laundry main drain shall connect to the building drain a minimum of 40 pipe diameters upstream and downstream of any soil or waste stack.

3. A suds relief vent shall connect to the laundry main drain a minimum of 40 pipe diameters downstream from the base of the laundry stack. The suds relief vent shall connect to a vent a minimum of two branch intervals above the base of the laundry stack.

4. The Inspector may permit a variation from the above requirements when conditions will not allow compliance.

10.15: Example 4 - Laundries Installed on More Than Three Branch Intervals

SUDS PRESSURE RELIEF VENT
WASTE SIZE	RELIEF VENT SIZE
2"	2"
2"	2"
2-1/2"	2"
3"	2"
4"	3"
5"	4"
6"	5"
8"	5"

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(9)Sumps and Ejectors.

(a)Building Drains Below Building Sewer. Where it is not possible or practical for a drain to be discharged to the sewer by gravity flow, the drain shall be discharged into a tightly covered and vented sump, from which the contents shall be lifted and discharged into the building gravity drainage system by automatic pumping equipment.

(b)Sewage Pumps and Ejectors.

1. In single-family dwellings, a sewage-ejector sump receiving the discharge of toilets and other fixtures shall be equipped with a sewage-ejector pump having a full-size discharge and a minimum discharge capacity of 20 gallons per minute.

2. In all installations other than single-family dwelling, sewage-ejector pumps shall be equipped with a full-sized discharge and be sized in conformance with 248 CMR 10.15(10): Table 5: Determining Capacities of Sewage Ejectors.

3. The discharge piping from all sewage pumps and ejectors shall contain an accessible backwater or check valve and an accessible full port shut off valve installed downstream of the backwater or check valve. See 10.15: Example 5.

4. For systems not determined using 10.15: Table 5, a variance shall be required. Exception: Systems designed by a Massachusetts professional engineer.

10.15: Example 5 Discharge Piping from Sewage Ejector

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(c)Macerating Toilet Systems.

1. All macerating toilet systems shall be product accepted by the Board and in compliance with ASME A112.3.4 or CSA B45.9

2. Systems shall be suitable for the application and installed in accordance with the product manufacturer's installation instructions.

3. Shall have a minimum three-quarter inch discharge.

4. With the exception of toilets, all fixtures connecting to a macerating system shall be properly trapped and vented prior to connecting to the pumping unit.

(d)Pneumatic Ejectors.

1. The air pressure relief pipe from a pneumatic ejector shall not be connected to the regular venting system but shall be vented independently to the atmosphere through the roof.

2. The relief pipe shall be of sufficient size to relieve air pressure inside ejector atmospheric pressure within ten seconds but shall be not less than one inch in diameter.

(e)Grinder Pumps. Shall be product accepted, installed in accordance with the manufacturer's installation and with 248 CMR 10.15(6)(b)1.d.

(f)Duplex Equipment. Sewage pumps and ejectors, in other than one- or two-family dwellings receiving the discharge of six or more toilets shall be provided with duplex pumping equipment.

(g)Connections to the Building Drainage System. The discharge piping from a sewage pump or ejector shall be connected independently to the building drainage system.

(h) To calculate the discharge capacities of sewage pumps and ejectors, the following procedures shall be used.

1.248 CMR 10.15(9): Table 5.

2. Any installation that does not meet the requirements of 248 CMR 10.15(9): Table 5 shall be designed by a Massachusetts professional engineer.

Table 5

Determining Capacities of Sewage Ejectors

Number of toilets to be Served by each Ejector	G.P.M. Discharge of each Pump
1	20
2 - 3	75
4 - 5	100
6 - 7	125
8 - 10	150
11 - 15	200
16 - 20	250
21 - 25	300
26 - 30	350
31 - 35	375

(i)Ejectors Handling Other Fixtures. Generally, there will be a certain number of fixtures other than toilets emptying into the ejector sump. If the total amount of these fixtures exceeds four times the number of toilets used, the G.P.M. of the ejector pump should be increased at the rate of three G.P.M. for each fixture exceeding four times the number of toilets :

Example

GPM Pump Discharge of four Toilets	100 GPM
Number of additional fixtures to be handled	20
Excess Fixtures as calculated from above 20 - (4 x 4) = 4	4
Four @ 3 GPM	12 GPM
Correct Sewage Ejector Pump to use	112 GPM

(j)Individual Fixture Pumps.

1. Individual fixtures other than toilets, urinals or similar fixtures may discharge directly into:

a. a fixture mounted pump; or

b. into sumps and receivers with ejectors or pumps.

2. Individual fixture pumps may be used for sinks when unusual building structure conditions prevent the discharge of liquid waste by gravity.

3. Direct-mounted individual fixture pumps may be manually or automatically operated.

4. The individual fixture pumps shall be vented in accordance with the manufacturer's instructions. If individual fixture pumps provide an adequate water seal in accordance with 248 CMR 10.03 additional traps shall not be required.

(10)Drainage Fixtures Subject to Backflow.

(a) Backwater valves may be installed in drain piping which receives the discharge only from fixtures or drains subject to backflow from the public sewer system. All other drains which are not subject to backflow shall not drain through a backwater valve. See 10.15: Example 6.

(b)Materials for Backwater Valves. Backwater valves shall have all bearing parts of corrosion-resistant material.

(c)Diameter of Backwater Valves. Backwater valves, when fully opened shall have an effective opening not less than that of the pipes to which they are installed.

(d)Location of Backwater Valves. Backwater valves shall be installed so their working parts will be accessible for service and repairs.