A plumbing system is our home’s lifeline, yet most of us only think about it when some issues arise, creating lots of stress and confusion. You might think Why is it important? A basic understanding could help one avoid being misled by service providers and help them handle simple issues like a clogged sink.
In this blog, we will explore the “One Pipe System of Plumbing”, an older plumbing design that is still available in many old building structures. We will see how this system functions, compare it with the modern two pipe system, and highlight their key differences. Such knowledge would therefore assist you in making sound decisions regarding your home’s plumbing and in more effectively handling any problems.
What is a Plumbing System?
A plumbing system refers to a network of pipes and fittings designed to provide water and take away waste. This covers pipes for supplying water, traps, soil and waste pipes, plumbing fixtures, vents, building drains, sanitary and storm sewers, and some water treatment devices.
The main purpose of a plumbing system is to deliver clean, drinkable water throughout your building or home and to handle the removal of all water-related waste.
Now that you understand the basics, here are the four main types of plumbing systems:
- One Pipe System of Plumbing
- Two Pipe System of Plumbing
- Single Stack System Plumbing
- Single Stack Partially Ventilated System Plumbing
One Pipe System of Plumbing
This is an older plumbing design that connects wastewater from sinks, baths, washbasins, and toilets directly to the main drainage system, eliminating the need for gully traps and separate waste pipes. To maintain the water seal in the traps, a separate vent pipe is used to ventilate the traps of toilets, basins, and other fixtures.
Here’s how it works:
- Wastewater Collection: All wastewater from toilets, sinks, and showers flows into a single main vertical pipe, called the “stack,” that runs from the lowest floor to the roof.
- Ventilation: The stack is vented to maintain proper air pressure. A vent pipe extends from the top of the stack and exits through the roof. This allows fresh air in, helps wastewater flow smoothly, and prevents the siphoning of water from traps.
- Gravity Drainage: Wastewater flows down the stack by gravity. As it moves from higher floors to lower ones, gravity helps carry it to the sewer or septic system.
- Branch Lines: Individual fixtures are connected to the main stack through branch lines. These lines include traps, which are U-shaped bends that hold water. The water in these traps blocks sewer gases from coming into the building.
- Roof Vent: A vent at the top of the stack lets sewer gases escape into the air and helps keep the right air pressure inside the system.
Two Pipe System of Plumbing
This system is commonly used in India, especially when fixtures can’t be placed close together.
It uses two pipes: The soil pipes collect toilet waste, which connects directly to the manhole or drain, while the waste pipes collect water from the kitchen, bathrooms, and house cleanings, which are connected to the drain through a ventilated gully trap.
Here’s how it works:
- The gully trap collects waste from baths, basins, and sinks. It keeps these wastes separated from the main drain to prevent odors.
- The main soil vent pipe extends above the roof to release gases safely, away from people.
- A vent cowl made of corrosion-resistant material is placed at the top of the vent pipe to prevent birds from nesting.
- A cast-iron duck foot bend is preferred at the bottom for durability.
Single Stack System
In this system, all waste from bathrooms, sinks, and toilets is discharged through a single vertical pipe, known as the Soil and Waste Pipe (S.W.P). This system is both simple and cost-effective because it uses only one pipe and does not include a separate vent pipe. Its effectiveness can only be ensured by keeping a minimum 75 mm depth water seal so that no sewer gases can enter the building.
Single Stack Partially Ventilated System
This system is an upgraded version of the single stack and one pipe system of plumbing. A single common soil and waste pipe (S.W.P.) is used for the disposal of all waste from toilets, basins, and sinks in this system. Relief vent pipes are installed at every toilet, which provides necessary ventilation for their traps to avoid siphoning problems and maintain water seals. However, the basins, showers, and sinks do not have individual vent pipes.
Difference Between an One Pipe and a Two Pipe System
| Feature | One Pipe System of Plumbing | Two Pipe System of Plumbing |
| Uses a single main vertical pipe for both waste and ventilation | Uses two separate pipes: one for soil (toilet waste) and one for waste (kitchen, bathroom, etc.) with additional vent pipes |
| All wastewater (from toilets, sinks, and showers) flows through one pipe | Wastewater is separated into two different pipes: soil and waste |
| Requires a separate vent pipe connected to the main pipe | Separate vent pipes handle ventilation independently |
| Older or smaller buildings | Modern and multi-storey buildings |
| Does not typically use gully traps or grids | Uses gully traps with mesh or grid to separate waste |
| Higher risk of flooding or blockages due to a single pipe system handling all waste | Lower risk due to the separation of waste and soil pipes |
| Relies on the vent pipe to manage odors and prevent siphoning | Better odor control due to separate venting for soil and waste pipes |
Today, two pipe systems are more common because they separate drainage and ventilation into two different pipes, which reduces the problems seen with one pipe system of plumbing. However, you might still find one-pipe stack systems in older buildings, which may need updates to meet modern standards.
Comparison of 4 Types of Plumbing Systems
| Parameter | One Pipe System of Plumbing | Two Pipe System of Plumbing | Single Stack System | Single Stack Partially Ventilated System |
| Very good | Best and most effective | Less effective than the one pipe system of plumbing | Good, but not as efficient as the two-pipe system |
| More costly than partially ventilated single stack | Higher cost due to many pipes | Lower cost due to fewer pipes | Lower cost compared to the one pipe system of plumbing |
| Suitable for older or medium-sized buildings | Suitable for large, modern, and multi-storey buildings | Suitable for small buildings | Suitable for medium-sized buildings |
| Requires safeguards to ensure effective drainage and proper water seals | Fewer traps are needed, which is favorable | Same as one pipe system of plumbing | Same as one pipe system of plumbing |
Conclusion
Plumbing in our house can be greatly influenced when we analyze the differences between one pipe plumbing system and two pipe systems. The one pipe system of plumbing might still exist in older buildings, but its simplicity makes it less efficient compared to the two pipe plumbing system, which is suitable for modern homes because it can separate wastes. With this knowledge, you would be able to make informed decisions about plumbing issues that are minor and that you can undertake on your own.
If you are thinking about upgrading your plumbing or if you need expert advice, don’t hesitate to call an experienced plumber for an efficient and up-to-date system. A properly maintained plumbing system adds comfort to your home while preventing future troubles and expensive repairs.
Frequently Asked Questions
What Is a Two Pipe System?
A two pipe drainage system consists of two distinct pipes: one for soil waste (such as toilets) and the other for other types of waste (from kitchens and bathrooms). Each pipe is intended for different kinds of waste and connects to the main drainage system.
What Is a One Pipe System of Plumbing?
In this plumbing system, all waste from sinks, baths, and toilets goes through a single pipe directly to the drainage system. This system doesn’t use gully traps or separate waste pipes, and the vent pipe must be at least 50 mm in diameter.
What Is the Advantage of a Two Pipe System?
A two pipe system keeps sewage separate from other wastewater, prevents sewage from backflowing into waste fittings if the soil pipe is blocked, and allows wastewater to be used for irrigation or gardening.
What are the Advantages of the One Pipe Plumbing System?
The one pipe system of plumbing combines aspects of both one pipe and single stack systems. All waste from toilets, baths, as well as sinks, goes through a single pipe; thus providing a compromise between simplicity on the one hand and efficiency on the other hand.
Which Pipe System is Costly?
The two pipe system comes at a higher price because it uses four pipes: one for soil liquid waste, another for general solid wastes, and two for ventilation. The soil pipe directly links with the drain, while the waste pipe connects through a gully that has been trapped.
