Drinking water can only be distributed effectively between faucets, showers, toilets and other plumbing fixtures if it is supplied with sufficient pressure. Minimum flow and pressure values for New York City are specified in Chapter 6 of the New York Plumbing Code and vary depending on the specific type of fixture. The required values for some of the most common plumbing fixtures are as follows:
| TYPE OF FIXATION | MINIMUM FLOW RATE (GPM) | MINIMUM FLOW PRESSURE (PSI) |
| Bathtub, no shower | 4 | 20 |
| Dishwasher, residential | 2.75 | 8 |
| drinking fountain | 0.75 | 8 |
| Washbasin | two | 8 |
| Bath | 3 | 8 |
| Sink, residential | 2.5 | 8 |
| Sink, service | 3 | 8 |
| Urinal, valve | 18 | 20 |
| WC, tank, single piece | 3 | 20 |
The New York Plumbing Code establishes these minimum pressure and flow values for all operating conditions, even during peak demand when multiple plumbing fixtures are being used simultaneously.
Our plumbing engineers can help you select the best water booster pump for your building.
Do you have low water pressure?
If the water supply pressure is insufficient to meet the pressure and flow values required for hydraulic installations, a water pressure increase system must be installed. There are three main options permitted by the New York Plumbing Code:
- An elevated water tank
- A hydropneumatic pressure amplifier
- A water pressure booster pump, which is the subject of this article
Keep in mind that the need for a water booster pump is partially determined by the characteristics of the building; Since minimum pressure and flow values are specified at the equipment outlets, the likelihood of needing a booster pump increases for taller buildings.
The New York Plumbing Code requires that all booster pumps be equipped with a low-pressure cutoff switch, which prevents the creation of a vacuum when pressure on the suction side reaches values of 10 psi or less. When negative pressure is not accounted for, a phenomenon called cavitation occurs, where small bubbles quickly form and collapse in running water. Cavitation can cause localized shock waves, damaging the booster pump impeller and inducing mechanical vibrations, which also affect the motor that drives the pump.
The use of a single booster pump for more than one building is not permitted by the New York Plumbing Code except in multi-building projects that have a common owner. An individual water consumer is not authorized to supply pressurized water to neighboring buildings.
Checklist before installing a booster water pump
Keep in mind that low pressure and flow rates at equipment outlets have many possible causes, and you should not immediately assume that low water supply pressure is to blame. Before installing a water pressure booster pump, make sure the problem is not due to one of the following causes:
- Clogged water pipes can cause a drastic drop in pressure between the service inlet and the point of consumption, which is a common problem in older installations.
- Undersized pipes, a common result of poor plumbing design, can have the same effect as clogged water pipes.
- You may also have a partially closed shutoff valve causing a pressure drop, and the solution is as simple as opening it fully.
In either of these scenarios, installing a water booster pump is a waste of money and excessive pressure can damage your installation. Even if there is no damage, you will be wasting electrical energy to run the booster pump, and excessive pressure will increase the flow rate, also increasing your water bill. Before proceeding, make sure you do not have a partially closed valve and have your installation professionally assessed to ensure there are no piping problems.
Increasing the efficiency of water booster pumps
As with all electric motor-driven equipment, energy can be saved if a booster pump is equipped with a frequency inverter (VFD) for speed control. For fractional horsepower motors, such as those used in small residential applications, electronically commutated motors (ECMs) are a more economical option than VFDs.
There are several reasons why it makes sense to implement speed control for a booster pump:
- The required pressure increase may vary depending on current building conditions. For example, it may not be necessary when water demand is low.
- Pressure variations can also be caused by the utility company. For example, low pressure problems may only be present when the water distribution system is experiencing peak demand.
- Frequency inverters can be used to soft-start a water pressure booster pump by avoiding the starting current, which is typically five to eight times the rated current. In the absence of a soft starter, this inrush causes a sudden drop in voltage, which can damage sensitive electronic devices.
When a Water Pressure Booster Pump is equipped with speed control, its operation can be adjusted in real time in response to building and water supply conditions, maximizing energy efficiency. In fractional horsepower applications, electronically commutated motors offer the highest energy efficiency available while offering integrated speed control. For higher power pumps, typically used in commercial applications, the best possible combination is to have a three-phase motor with NEMA Premium efficiency equipped with a frequency inverter.
Reducing installation cost
Both pumps and electric motors are highly price sensitive to rated capacity and their efficiency is reduced when operating below their rated power. Oversized installations are expensive and inefficient, therefore it is highly recommended to hire a qualified engineering firm for design and specification.
The initial cost of the water boost system can also be reduced if the motor uses a higher voltage rating. For example, a 460-volt motor draws only half the current required by a 230-volt motor, assuming they both have the same power rating. Since electrical circuits are sized based on current and not voltage, the circuit for the high voltage motor is the cheapest.
Final Observations
Water booster pumps are required when the pressure and flow provided in individual plumbing fixtures do not meet code requirements. However, before installing the system, it is important to confirm that the low pressure is not due to other factors, such as clogged or undersized piping. A water pressure booster pump offers maximum performance when properly sized and equipped with a high-efficiency motor and speed control.
Editor's Note: This post was originally published in November 2016 and has been reworked and updated for accuracy and comprehensiveness.
