PROVIDENCE — Although the installation of new cesspools has been banned in Rhode Island since 1968, cesspools are officially on the way out.

On June 18, the House passed a plan to phase out all existing cesspools in the state, which stands at about 25,000. For decades, cesspools have been considered harmful to the environment and public health. As covered pits lined with brick or concrete blocks, cesspools do little to contain the spread, under or above ground, of excess sewage into drinking water supplies and waterways. They have been linked to beach and shellfishing closures, especially in Greenwich Bay, where cesspools from Warwick neighborhoods have been blamed for discharging polluted runoff into the watershed.

According to the legislation, cesspools contain bacteria, viruses, ammonium and pollutants that cause algae blooms. They also accumulate phosphates, chlorides, grease and chemicals used to clean cesspools.

The cesspool ban also has been given urgency from the threats posed by climate change. Flooding, sea-level rise and more extreme weather increase the likelihood of overflowing cesspools.

In 2007, the General Assembly passed a bill requiring the phase out of cesspools within 200 feet of a shoreline, wetland or drinking-water supply. Efforts in recent years to expand the phase-out to all cesspools have been defeated by neighborhood groups concerned about the cost — about $12,000 — of upgrading to a state-approved septic system or connecting to public sewer. Real-estate agents also opposed efforts to require cesspool closure when a property changes hands, saying it would hurt sales.

During the recent House debate, Rep. Joseph Trillo, R-Warwick, offered a failed amendment to exempt cesspools located near municipal water supplies.

“We’re going to screw the 25,000 people in Rhode Island that have cesspools,” he said, after conceding that that bill would pass.

To help with the cost, the state offers two loan programs for cesspool replacement and public-sewer connection. Exemptions can also be granted for financial hardship.

The legislation doesn’t require the immediate closure of cesspools, but instead mandates that a septic system or sewer hook-up occur within a year of a property changing hands. There are exemptions for low-income property owners.

An identical bill passed the Senate on May 27. The bill heads to the governor for signing.

After the 62-9 vote, state Department of Environmental Management (DEM) director Janet Coit called the vote “a great victory.”

The law would take effect Jan. 1. DEM has four field inspectors that inspect and review cesspool upgrades. They perform about 425 closures each year and have the capacity to perform up to 1,000 reviews annually, according to Coit.