Restoration Guide: HVAC Drain Waste and Vent

Jeffrey Anderson

Editor's Note: This is article 13 of 16 in Chapter 8: The HVAC/Plumbing Guide of Old House Web's Home Restoration Guide. This guide was developed and edited for old homes from original materials in the U.S. Housing and Urban Development (HUD) Rehab guide.


Just like water distribution systems, drain, waste, and vent systems have evolved over the years. The waste system in your old house may be made up of cast iron, lead, plastic, or a combination of all of them. Your old house might have even been built before the need to have a vent system to aid drainage was realized.

This article takes a look at the drain, waste, and vent systems found in old homes, and ways you might improve or replace then during a home restoration.

Section 1--Overview

You may have already noticed problems with the drain, waste, and vent systems of your old house. If you have noticed sewer odors or have drains that seem to take too long to empty, there is a good chance that there is a problem with your drain system.

Drain and waste systems were initially designed to work using gravity and venting to encourage proper drainage. Homes can settle lower over the years, and if the drainage slopes of the waste lines in the home have been disturbed, slow drainage might be the result. If your old house was built before venting was used, or has vents that are incorrectly sized, the speed of your drainage can be affected, and there is the potential for the buildup of toxic gases.

All old homes should have their drain, waste, and vent systems inspected for proper operation and safety. Earlier models of drainage systems allowed potential contamination of potable water and should be checked. A home renovation is a good opportunity to improve, restore, or replace the drain, waste, and vent system in your home.

Section 2--Materials in Drain and Waste Systems

Many different types of materials have been used for drain and waste systems over the years, and if you are only replacing some components of the system, it is usually possible to find adapters that allow you to combine different types of fittings.

Several problem areas in your drain and waste system might require a completely new design for your home's system. A new design may not only improve your system's drainage capabilities, but it could also reduce your water usage. The following suggestions might help improve the waste and drain systems in your old house.

2.1: Cast Iron Drain, Waste, and Vent (DWV) Piping

Cast iron piping was once popular for home waste systems, but its use dwindled as other materials were approved for waste systems. Cast iron is approved by most plumbing codes, is fireproof, and is excellent in bathroom areas due to its sound insulation qualities.

2.2: Copper DWV Piping While Remodeling

Copper piping was also once popular for home waste systems, but like cast iron, its use dwindled when other material were introduced. Copper is lightweight, approved by most codes, and easy to work with.

2.3: Acrylonitrile Butadiene Styrene (ABS-DWV) and Polyvinyl Chloride (PVC-DWV) Piping

These are plastic waste and drain piping materials and are popular with modern remodeling and new home construction. They are inexpensive compared to copper and cast iron and require less labor to install. Most plumbing codes allow their use, but sometimes not below grade. Plastic piping requires nail plates to prevent accidental puncture, and transmits noise more than cast iron and plastic.

Section 3--Using Pump sand Ejectors to Discharge Waste

Sometimes due to foundation settlement or the location of a plumbing fixture, gravity drainage will not work. Sewer pumps and ejectors help waste material exit the home through the drain lines. Installing these units can be expensive, but in some cases there is no choice, especially if a basement bath is below the grade of the sewer line exiting the home. Before installing one of these units, check for local code restrictions.

Section 4--Gray Water and Heat Recovery Devices

Efforts are being made to make residential drain, waste, and vent systems more energy efficient and reduce their use of natural resources. Gray water systems recycle water from showers, washing machines, bath tubs, and sinks for irrigation use. Not all jurisdictions allow the use of these systems due to concerns about contamination of potable water.

Heat recovery devices use the remaining heat in waste water from showers, washing machines, and dishwashers to help warm cold water entering the hot water heater, thereby reducing hot water heating energy costs.

Section 5--Install an Air Admittance Valve during Your Home Restoration

Air admittance valves are a relatively recent innovation designed to help venting in difficult-to-reach places. They allow air to enter pipes, but don't let gases out. These devices are popular in Europe, but in the U.S. air admittance valves are not approved for use in some jurisdictions.



About the Author

Jeffrey Anderson has a Degree in English from V.M.I. and served as an officer in the Marine Corps. He worked in Residential and Commercial construction management for 25 years before retiring to write full time.

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