8.2 Piping, Valves & Controls

8.2 Piping, Valves & Controls

Quick Answer: Run each fixture branch to a shutoff, keep connectors at 30 inches or less (except dishwashers, washers, and icemakers), size branches from 248 CMR 10.14 Table 1, drop pressure to 80 PSIG with a downstream 0–150 gauge, and put full-port control valves at the meter, risers, and multi-family units.

The CIB gives this topic three items. Almost all of them live in 248 CMR 10.14, not 10.10. Treat 8.2 as the valve and branch-pipe chapter. Deep water-service and backflow tables stay with the water chapter; you still need the pressure-reducing valve trigger, check-valve prohibitions at heaters, mixing-valve temperature limits, and solenoid water-hammer rules because they are how fixtures actually get water.

Fixture branches, connectors, and Table 1

From the meter (or the main control valve when there is no meter), cold-water piping to every branch, riser, and fixture is sized from demand. 248 CMR 10.14(2)(a):

1. Size the fixture supply from Table 1.
2. Size mains, branches, and risers from Tables 1, 2, and 3, unless a Massachusetts professional engineer designs the system.
3. Apply the Table 2 demand factor to get capacity, then pick the pipe from Table 3.
4. Extend the individual fixture branch to the fixture connector and terminate with a fixture shutoff valve.
5. Fixture connectors shall not exceed 30 inches and shall be product-accepted.
6. Exception to the 30-inch cap: dishwashers, washing machines, and icemakers.

That last pair is a classic two-part item: the branch still ends at a shutoff, but those three appliances may use a longer product-accepted connector.

Table 1 — Minimum sizes of individual fixture branches and factor values (Cornell 248 CMR 10.14):

Memorize the outliers. Tank-type toilets and lavatories are ⅜ inch, not ½ inch. A flush-valve toilet jumps to 1 inch and factor 12. A multiple-head shower valve is ¾ inch and factor 6, the same band as a flushometer urinal. The code's worked example for a one-family house (two tank toilets, two lavatories, tub, shower, laundry, dishwasher, kitchen, two hydrants) totals factor 28 on the cold side. Table 2 demand factor 0.50 for a one- or two-family dwelling gives capacity 14, which Table 3 places on 1-inch pipe (9.1 to 16.5).

Table 4 (minimum flow pressure / maximum flow rate) is the other sizing companion: most faucets want 8 psi; flushometer toilets want 15–20 psi; shower heads 2.0 GPM except emergency showers.

Building control valves — the skeleton of the system

All valves shall be accessible (10.14(3)(a)). Then build the valve map:

Dead ends are not allowed. Saddle valves are prohibited. Do not tap, burn, weld, or drill a water line except with a Board-accepted mechanical penetrating device.

Individual fixture shutoffs versus appliance valves

248 CMR 10.14(3)(f)1: in all buildings, water pipes feeding plumbing fixtures, devices, or appurtenances get a valve that shuts off that fixture, device, or appurtenance. Exception: residential shower valves, tub and shower valves, tub fillers, and other similar type fixtures. Those mixing valves are the control; the code does not pile a separate stop in front of a residential shower valve the way it does in front of a lavatory.

Keep three categories distinct on the exam:

1. Plumbing fixture shutoffs — 10.14(3)(f) stops at lavatories, tanks, urinals, kitchen sinks, hydrants, and most other fixtures.
2. Appliance connectors — dishwashers, clothes washers, and icemakers may exceed 30 inches, still on product-accepted connectors, still on Table 1 branches. Their integral solenoids are why the next subsection exists.
3. Fuel-gas appliance valves — gas cocks at a gas-fired water heater, range, or dryer are 248 CMR 4.00 / 5.00 (Massachusetts Fuel Gas Code / NFPA 54 amendments), not 10.14 fixture stops. A plumbing shutoff on the cold-water branch above a water heater is 10.14(3)(h). A gas appliance valve on the same heater is gas fitting.

Pressure-reducing valves (intro), check valves, mixing valves, solenoids

Excessive pressure (10.14(2)(e)): if pressure at any plumbing fixture, device, or appurtenance exceeds 80 PSIG, install a pressure-reducing valve on the piping upstream of that device to limit pressure to 80 PSIG. Install a pressure gauge with a minimum range of 0–150 PSIG within 24 inches downstream of the reducing valve. Exception: water-service piping upstream and downstream of a water pressure booster. Inadequate street pressure goes the other way: one-, two-, and three-family dwellings get a sized booster pump; larger buildings need a Massachusetts PE design. Leave PRV internals, bypasses, and thermal-expansion interaction for the water chapter once this trigger and gauge rule are solid.

Check valves appear in three exam-relevant places:

• Do not install a check valve in the cold-water supply to a hot-water heater or storage tank (10.14(6)(c)1). That is how you trap expansion and cook a tank. A properly sized thermal expansion tank may be installed instead (10.14(6)(c)2). If a meter already contains a check or backflow preventer, creating a closed system, install a sized expansion tank as close as possible to the metering device (10.14(3)(j)).
• Central shower mixing valves require check valves on both hot and cold inlets (10.10(4)(c)5.b).
• Combination potable / space-heating loops use check valves in the Board's 2012 diagram; that system is section 8.3.

Mixing valves are the temperature cops. Shower and tub fillers: 120°F mixed-water limit, product-accepted thermostatic, pressure-balancing, or combination valves, plumber-adjusted before inspection. Public and employee lavatories, residential tubs, and combination potable / space-heating fixture outlets also land on the 10.14(5) table. Combination space-heating systems must have a mixing valve serving the plumbing fixtures (10.14(6)(g)5) so 140°F coil water never reaches a shower arm.

Solenoid / quick-acting valves (10.14(2)(b)): any building water system that includes quick-acting or solenoid valves needs devices that absorb the high pressure from sudden closure. Use air chambers that can be restored if they waterlog, or other product-accepted mechanical arrestors. Place them as close as possible to the quick-acting valve and keep them accessible. Mechanical devices may also sit at the ends of long runs or on piping serving batteries of fixtures, following the manufacturer. Clothes washers, dishwashers, and icemakers are the usual solenoid sources on a house job.

Residential hose outlets sit no more than 100 feet apart. Commercial buildings only owe sillcocks in mechanical rooms, penthouses, or similar mechanical areas — but every hose-thread outlet still gets a vacuum breaker or backflow preventer.

Exam traps for 8.2

• 30-inch connectors are the default. Dishwashers, washers, and icemakers are the named exception, not "all appliances."
• Table 1 tank toilets and lavatories are ⅜ inch. Guessing ½ inch is the common miss.
• 80 PSIG is the PRV trigger, and the gauge is 0–150 within 24 inches downstream, not on the street side of the valve.
• Residential shower valves do not need a separate fixture stop. Lavatories do.
• No check valve on the cold inlet to a heater. Expansion tank, yes; check valve, no.