A plumbing permit is not needed for the direct replacement of any plumbing fixture, except for a water heater. However, if a fixture location is changed, a permit is required. In other words, you can remove a toilet and replace it with a new one without the need for a permit. But, if you move the closest flange in any way, a permit is required. This is true for all plumbing fixtures.

The authority having jurisdiction determines the provisions for licensing. State Plumbing Boards determine requirements and provide testing of qualified applicants to become licensed. Plumbing inspectors enforce codes adopted by the AHJ.

It is common for modern DWV systems to be tested with air. In the old days water was the most common means of testing. When there is a leak that cannot be found easily, smoke can be used to expose the leak location. Smoke is not used as a primary test method. Air is the test medium of choice. The testing of a DWV system is to be conducted for a minimum of 15 minutes. The minimum test pressure is required to be 10 pounds per square inch (PSI). If only underground plumbing is being tested there must be one riser that is at least ten feet above the main plumbing system.

Some pipe manufacturers list measurement in one foot increments when rolls of pipe are 100' or over, but do not list increments on joints of 21', 20' or less. Brand names, psi rating, and nominal pipe size are required.

Handicap toilets are available with heights that include 16 inches, 18 inches and 20 inches. Eighteen inches is the most common height of a standard handicap toilet.

The minimum unobstructed opening of egress for a shower door installed on a typical shower is 22 inches.

An air gap is believed to be superior to an air break for the protection of an indirect wastepipe from back siphonage. Due to the nature of installation there is more risk of a backflow occurring with an air break. Since air breaks have discharge piping entering a receptor it is feasible to have the sanitary drain become clogged and back up, which could result in contaminated waste traveling back to the indirect waste fixture. This is not possible when an air gap is used.

Minimum vertical distance from the bottom of an indirect drain line to its receptors flood rim is 1".

Combination-waste-and vent (CWV) systems do not require independent vents on all fixtures. Instead of a vertical vent the fixtures approved for a CWV installation are installed with oversized drains. Due to the larger drain diameter the fixture obtains the needed air for drainage in the top section of the oversized piping. Urinals, toilets and bidets are not allowed to be installed on CWV systems.

The plumbing code allows a maximum of eight fixtures connections to a horizontal branch drain. This is also called a circuit vent.

Under the IPC, a cleanout is needed for every change of direction exceeding 45 degrees.Also, when there is more than one change of direction in a run of pipe, there needs to be a cleanout for every 40 feet of developed length.Using these standards, we need 1 cleanout for the 90 degree turn and 1 cleanout for the 40 feet of developed length.
 
Under the UPC, a cleanout is needed for every 100 feet of developed length of pipe or a fraction thereof.Furthermore, a cleanout is needed for every aggregate change of direction that exceeds 135 degrees.Using these standards, we need 1 cleanout for the distance, 40 feet, which is a fraction of 100 feet, and 1 for the aggregate change in direction since it goes over 135 degrees.

Not more than one trap is permitted on a trap arm.

All flexible water connections are required to be accessible. This means that they can be concealed in a cabinet or behind an access panel, but they must be accessible.

Vacuum breakers are normally used to protect water heaters, sill cocks and hose bibs from backflow dangers.

The amount of grade, also referred to as pitch or fall, for a drain pipe is determined by the size of the drain pipe. Master plumbers and other design professional establish these elements of a plumbing system based on the minimum standards required by local code requirements. As a general rule-of thumb, the proper amount of grade for a drain up to 4-inches in diameter is .25 inch per liner foot.

At the reduction point, because of the direction of flow, waste can build up which will result in ping system blockage.

Exhaust must be discharged outdoors in a way which will minimize the hazard of noise
and contamination to the environment.

Flux may only be used to braze dissimilar metals.

Such markings shall be in an accessible position outside of the tank, permanently affixed.

1.5" is the minimum depth size for a drip pan.

Any gray water going into a gray-water collection reservoir is required to be filtered. This is required as a means of blocking solids from entering the collection reservoir. While the fixtures allowed for the recycling of gray water should not be transporting solids there is always a possibility the some type of solid could find its way into the drainage water. The filters stop these impurities from reaching the collection of gray water that will be recycled.

The maximum allowable time for the retention of gray water that will be used to flush toilets or urinals is 72 hours. Holding water for long periods of time can result in the growth of bacteria. This bacteria is not wanted in the plumbing system. For example, green water in a toilet tank is not appealing and could present health hazards. When a gray water recycling system is sized properly the water retained in a collection reservoir would be balanced to the fixtures served and the normal daily use of the fixtures will draw down from the reservoir often enough to avoid prolonged water storage.

Gas piping in not allowed to be installed in laundry chutes, dumbwaiters, air-circulating ducts or elevators. The chutes, shafts and ducts can transport gas to various locations in a building if a leak should occur. Therefore, it is inappropriate to install gas piping in a location that could distribute gas beyond the location of the leak.

Flow controls on gas systems are installed to keep the operating pressure of the system lower than the supply pressure for the system. These devices prevent excessive pressure from the distribution system. They must be approved and suitable both the inlet and outlet gas pressure for the application. The flow controls must be readily accessible.

Degree of Angle = Fitting x 360 Degrees
Degree of Angle = 0.125 x 360 Degrees
Degree of Angle = 45 degrees

Pressure = Height x Amount of pressure exerted at base of a one foot stack
P = 15 x .434
P = 6.51 psi