How to Design a Plumbing System for a Building (2023)

As a homeowner, the choices you make when planning home improvement projects such as toilet upgrades or installing new bathrooms also affect plumbing design. An efficient plumbing system begins with a design that focuses on water and energy saving. In this guide, we will highlight tips on how to design a plumbing system for a building.

Factors to Consider When Designing a Plumbing System

When designing a new plumbing system for a bathroom, kitchen, laundry, and other rooms that require plumbing networks, there are several factors to consider:

1. Plumbing Codes

Typically, plumbing installation and design must adhere to the local building codes to ensure legal and safety compliance. Plumbing codes limit the number of plumbing fixtures that can be installed on a vent stack or drain system. The number of supply lines and drains that must be placed inside walls is also limited. It is important to check with your local building jurisdictions to get information about the applicable codes as well as situations when they can deviate from the standard codes.

2. House Design

Water supply to a building is one complete system that transverses various rooms. Both the clean water supply system and the DWV (drain, waste, and vent) systems are often designed to run alongside each other to save on materials and enhance water efficiency. When working on any home improvement project, consider grouping rooms that require plumbing fixtures close together. For example, a new bathroom should be installed adjacent to a bedroom while a laundry area should neighbor a kitchen. 3. Water Supply, Hot Water System, and DWV

Water supply and DWV (drain, waste, and vent) systems should sit side by side inside the walls of your house. This design strategy helps to save on water and energy consumption. Ensure that your hot-water plumbing loop system continually moves hot water back to your water heater. This significantly reduces the amount of energy expended in water heating. You could also opt for a solar hot water system or a point-of-use tankless hot water unit. 4. Materials and Building Contractors

Opting for cheaper materials and inexperienced plumbers will likely cost you more in the end. To get the most out of your plumbing design, ensure that you only purchase the highest quality materials and hire a highly-rated contractor who comes with good recommendations. A poorly fitted joint or incorrectly sloped drain system can cost you lots of money to correct later on.

5. Plumbing Design Parameters

Plumbing design encompasses several parameters. Generally, the water supply system must be designed to deliver appropriate water pressure and flow. More importantly, the design should ensure that clean potable water is not contaminated by greywater from the DWV system. A good plumbing system must also be suitable for the various temperatures (hot or cold) of the water carried. A well-designed and installed plumbing system should also be durable, minimize noise from water flow, and ensure water efficiency. Generally, water supply systems consist of a combination of pipes, valves, and outlets. Some systems may also include storage tanks and pumps, and you must get all these parameters right to ensure that clean water is delivered at the appropriate rate and temperature and wastewater is eliminated safely and seamlessly.

Plumbing Design Parameters

In this section, we shall cover the following plumbing design parameters:

1. Water Pressure

If your aim is to enable building occupants to use water efficiently, then the right water pressure is important. Too low water pressure will inconvenience building owners, while too high pressure will lead to excessive water use and high wear on the plumbing system. Mains pressure systems will require pressure-reducing and pressure-limiting valves to control water pressure and temperature. Low-pressure systems, on the other hand, require fewer valves or controls and can be improved by storing water in overhead tanks or using a pressurizing pump. 2. Water Flow Rate

The Building Code requires that all sanitary fixtures and appliances receive adequate water supply at the right flow rate. If the flow rate is too high, it will result in water being wasted, while too low flow rate will mean that sanitary fixtures and appliances don't function properly. Flow rate is typically affected by water pressure, pipe diameters, and water temperature. A flow regulator can be installed to maintain constant water flow, independent of water pressure. 3. System Layout

During the design, the layout of the plumbing system will to a large extent follow room layout. However, there are several factors to consider depending on code compliance, user comfort, and sustainability. When planning a water supply layout, consider pipe runs and lengths, point of entry into the building, water heating system, and noise prevention. 4. Mains Connection

If the water supply comes from the mains supply, the utility operator is responsible for the flow rate and supply pressure to the property. The property owner will only take responsibility for the necessary pipework that brings water into the building. An isolating valve should be installed at the point of connection to allow easy maintenance and repair of water supply systems and plumbing fixtures as may be required.

5. Pipe Materials and Specifications

The supply pipes used in a property must not contaminate the potable water supply. They must be suitable for the flow rate, water pressure, and temperature of the water they will be carrying. The material used as well as wall thickness will also affect the specifications of supply pipes. Common supply pipes for domestic properties include polybutylene (PB), copper, polyethylene (PE), cross-linked polyethylene (PEX), and polypropylene (PP-3 or PP Type 3). 6. Flow Rate and Appropriate Pipe Size

All pipes must be properly sized to achieve the right flow rates in a plumbing system. The BOCA Plumbing Code sets out the required flow rates and pipe sizes for various fixtures such as basins, baths, sinks, showers, laundry tubs, dishwashers, and washing machines. It is important to ensure that the pipe sizes are appropriate to achieve the desired flow rates. 7. Backflow

Backflow refers to the unplanned reversal of the flow of water (sometimes water and contaminants) back to the water supply system. The plumbing system must be designed to prevent water contamination from backflow.

Wrap Up

Designing a plumbing system for a building requires careful consideration of various factors such as plumbing codes, house design, water supply, hot water system, materials, and plumbing design parameters. Adhering to these considerations will ensure a well-designed and efficient plumbing system that meets legal and safety requirements while promoting water and energy efficiency. By following these tips, you can create a plumbing system that not only functions effectively but also contributes to a sustainable and eco-friendly home.


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