Plumbing Performance Required by Code
By J. Andrew Reid

Well Manager® and Herculan ConstaBoost systems were designed to provide code required plumbing performance using wells that cannot adequately do so on their own.

The Problem
Plumbing companies involved in new work sometimes hear complaints about inadequate pressure from customers moving into a new home with a well. A majority of these complaints involve the master bath shower. After all, when you sign on the bottom line of a hefty mortgage, you expect a good shower.

In response the builder will send the plumber to verify that all of the plumbing work in the home is properly installed and functioning. The plumber will operate the fixture to see that there are no defects, clean screens and aerators and verify that a reasonable amount of water is coming from the outlet. If everything appears to be working the customer is referred to the well driller. When the driller arrives he checks out his equipment to see that it is functioning correctly, cranks the pressure switch up a few pounds and suggest that the problem may be caused by the code required flow restrictors in the new faucets.

At this point the homeowner has consulted everyone who has anything to do with his or her water system and no one has offered a solution. Still unhappy with the way the system is working, there is nobody left to talk to so they will just have to live with it. Most people live with the problem for years before they find out there is a solution. What they never find out is that the solution is code required and the inspector did not check the flow pressure in the system to find that it was inadequate and so never asked that the situation be corrected.

Flow Pressure
Flow pressure is the pressure in the water supply pipe near the faucet or water outlet while it is open and flowing.

Figure 1 shows flow pressure of 28 psi at a showerhead while it is the only fixture in the system that is running. Figure 2 shows 14 psi flow pressure at the same showerhead while two other showers are also running. Some codes suggest that satisfactory flow pressure is 15 to 20 psi. Many homeowners suffer with systems that deliver so little flow pressure that flow ceases from one outlet when others are in use.

Figure 1

Figure 2

The reason the plumber didn't see a problem is he was checking fixture operation not system performance. There was plenty of water at the shower when he opened the valve with nothing else running but performance will change at peak demand time when everyone in the house is getting ready to go to school and work.

The plumber and the inspector should have tried running all the showers at the same time or starting the washer or dishwasher while two of the shower were in use. In homes with a well, this test should be continued until the pressure pump brings the well pump on. Then they would see the system's performance as the homeowner does.

Code Requirements

For some inexplicable reason, new construction where the water source is a private well is not treated by inspectors in the same way as new construction connected to a water service even though most plumbing codes say they should be treated the same!

National Plumbing Code 2000: Adopted by many states, including New Jersey, Connecticut and Idaho as their code.

NPC 10.3.1
Buildings Plumbing fixtures shall be provided with a potable supply of water in the amounts and at the pressures specified in this chapter. (Chapter 10)

10.8.1 Water Pressure Booster Systems Required

When the pressure in the public water main or individual water supply system is insufficient to supply the potable peak demand flow to plumbing fixtures and other water needs freely and continuously with the minimum pressure and quantities specified in Section 10.14.3, or elsewhere in this Code, and in accordance with good practice, the rate of supply shall be supplemented by one of the following methods:

1. An elevated water tank
2. A hydro-pneumatic pressure booster system
3. A water pressure booster pump.

10.8.3, 10.8.4, 10.8.5, and 10.8.6 discuss the required features of a gravity or suction water supply tank.

Of the three options offered by the code, b. and c. will not work with a well system, but option a. will.

The descriptions in these sections don't say how high the tank must be elevated or exactly what they must be elevated above but tanks must have an overflow which terminates 6" above a roof drain, floor drain or properly trapped and vented fixture and need a drain at their lowest point. These requirements appear to rule out buried atmospheric tanks for potable water use.

10.14.3 Sizing Water Distribution Piping.

1. The supply demand in gallons per minute in the building hot and cold water distribution system shall be determined on the basis of the load in terms of water supply fixture units (WFSU) as shown in Table 10.14.2A and the relationship between the load in WFSU and the supply demand in gallons per minute (gpm) as shown in Table 10.14.2B. For fixtures having both hot and cold water connections, the separate hot and cold water loads shall be taken as 75% of the listed fixture unit value.
2. Main risers and branches of the water distribution system shall be sized based on the minimum available water pressure at the source, any elevation differences between the source and the fixtures, pressure losses in the distribution system, and the pressure (with flow) required at each connection of the fixture supply branches.

10.14.4 Inadequate Water Pressure

Whenever water pressure from the street main or other source of supply is insufficient to provide flow pressures at fixture outlets as required under Section 10.14.3, a booster pump and pressure tank or other approved means shall be installed on the building water supply system.

Comment: Although no one has ever asked me to design the water distribution system for a house with a well for an available source pressure of 20 psi, it would appear that they should have. If the plumbing system must be designed to the minimum pressure at the source that would be 20 psi in a system where the pressure switch comes on at 20 psi and goes off at 40 psi.

International Plumbing Code 2000: Adopted by many states, including Colorado and Arizona as their code.

602.1 General. Every structure equipped with plumbing fixtures and utilized for human occupancy or habitation shall be provided with a potable water supply of water in the amounts and at the pressures specified in this chapter.

602.3 Individual water supply. Where a potable public water supply is not available, individual sources of potable water supply shall be utilized.

602.3.1 Sources. Dependant on geological and soil conditions and the amount of rainfall, individual water supplies are of the following types: drilled well, driven well, dug well, bored well, spring, stream or cistern. Surface bodies of water and land cisterns shall not be sources of individual water supply unless properly treated by an approved means to prevent contamination.

602.3.2 Minimum quantity. The combined capacity of the source and storage in an individual water supply system shall supply the fixtures with water at rates and pressures as required in this chapter.

604.3 Water distribution system design criteria. The water distribution system shall be designed, and pipe size shall be selected such that under conditions of peak demand, the capacities at the fixture supply

Table 604.3
Water Distribution System Design Criteria Required
Capacities at Fixture Supply Pipe Outlets

604.7 Inadequate water pressure. Whenever water pressure from the street main or other source of supply is insufficient to provide flow pressures at fixture outlets as required under section 604.3, a water pressure booster system conforming to Section 606.5 shall be installed on the building water supply system.

606.5.1 Water pressure booster systems required. Where the water pressure in the public water main or individual water supply system is insufficient to supply the minimum pressures and quantities specified in this code, the supply shall be supplemented by an elevated water tank, a hydro pneumatic pressure booster system or a water pressure booster pump installed in accordance with Section 606.5.5.

Sections following this describe the various features of an elevated tank. They are very similar to those in the National Plumbing Code.

Uniform Plumbing Code 2000: Adopted by many states, including Texas and New Mexico as their code.

Definitions 218.0

Pressure - The normal force exerted by a homogeneous liquid or gas, per unit of area, on the wall of the container.

1. Static Pressure BB - The pressure existing without any flow.
2. Residual Pressure - The pressure available at the fixture or water outlet after allowance is made for pressure drop due to friction loss, head, meter, and other losses in the system during maximum demand periods.

608.1 Inadequate Water Pressure. Whenever water pressure in the main or other water source of supply will not provide a residual water pressure of at least fifteen (15) pounds per square inch (103.4 kPa), after allowing for friction and other pressure losses, a tank and pump or other means which will provide said fifteen (15) pound (103.4 kPa) pressure shall be installed. Whenever fixtures and/or fixture fittings are installed, which require residual pressure higher than (15) pound per square inch (103.4 kPa), that minimum pressure shall be provided.

Comment: This code does not use "flow pressure" but the definition of "Residual Pressure" appears to add up to the same thing. All of these codes seem to agree that the important consideration is the water flow available at each faucet during peak demand periods (with the other faucets normally associated with peak demand open).