Do Low-Flow Toilets Cause Sewer System Problems?

Low Flow High Efficiency-Toilets

Low-flow toilets have become popular in recent years. As the name suggests, low-flow toilets use less water, which is an important consideration in the drought-prone San Francisco Bay Area. However, there are possible downsides to low-flow toilet fixtures and the effect they can have on your sewer and plumbing system: things to keep in mind if you’re thinking about purchasing a low-flow toilet unit.

Let’s compare the benefits and drawbacks of installing low-flow toilets in a residential home or commercial business – and learn how to make your home plumbing system as efficient and sustainable as possible, whether or not you’re using low-flow toilets.

What Are the Pros and Cons of Installing Low-Flow Toilets?

Pros of Low-Flow Toilets

We love environmentally friendly bathrooms, and low-flow toilets (also known as low-flush toilets or high-efficiency toilets) are an attractive option for green households. The maximum water volume per flush allowed under US federal law is 1.6 gallons. Low-flow toilets use 1.3 gallons of water or less per flush. There are also dual flush models, which typically allow for a 1.3-gallon full flush or a 0.8-gallon reduced flush.


The primary benefits of low-flow toilets:

  • Water conservation – Sustainability is the primary reason for installing low-flush toilets because they use significantly less water than their full-flush counterparts. Over time, water-efficient toilets save thousands of gallons of water by limiting the amount used for each flush.
  • Cost savings – By using less water, your monthly water bill could be reduced significantly. According to the EPA WaterSense website, families can reduce water consumption by 20-60% if WaterSense labeled products such as low-flow toilets are installed in the home. WaterSense-approved fixtures can save “more than $140 per year in water costs, and $2,900 over the lifetime of the toilets.”
  • Space savings – Since they hold less water, low-flow toilet tanks are smaller and can fit into compact spaces. The difference in size may seem insignificant, but every inch counts when installing a toilet fixture in a tight bathroom.

Cons of Low-Flow Toilets

The major drawback of low-flow toilets is associated with transporting solids out of your house and into the sewer main. The low water volume in a low-flush toilet fixture can make it difficult to achieve sufficient outflow, which can leading to problems like clogging and unpleasant odors. In fact, the city of San Francisco’s push for low-flow devices in 2011 led to major problems for the sewage department when sewer mains around the city became backed up. The sewer system had been designed with a larger percentage of water in mind, and the resulting backups caused horrible smells across the city. These challenges mean it’s even more important to flush only waste and toilet paper when using a high-efficiency toilet.

A related issue is double flushing. Sometimes, these toilets need an extra flush to get everything down the drain, which unfortunately defeats the purpose of saving water. 

How to Troubleshoot Low-Flow Toilets?

If you are experiencing insufficient water pressure when flushing a low-flow toilet, there are some techniques you can use to fix the problem and help prevent future problems.

The most important preventative tip for problematic low-flush toilets is to avoid flushing trash or other non-human waste – or in some cases even avoid discarding toilet paper – into a low-flow toilet. Do not flush wipes, paper towels, or anything else that isn’t designed for toilet flushing. This is true of all toilet designs, but is especially important for low-flow toilet owners who want to avoid dealing with clogged drains.

It’s also important to keep in mind that chronically low water pressure could be due to your home’s overall water pressure, which is regulated by your local water service district. Homes in Oakland and the San Francisco Bay area typically have a pressure reduction valve on the incoming water line to ensure inflow pressure remains below 80 pounds per square inch (PSI). If your home’s overall water pressure is an issue, installing a supplemental booster pump may a good option. Booster pumps are similar to pumps used in well systems and increase water flow pressure throughout the home. Consult a qualified plumbing contractor before making any modifications to your home water system.

Before purchasing a booster pump, Oakland and East Bay homeowners and commercial property owners should report water pressure problems and if necessary, request flow and pressure testing from the East Bay Municipal Utility District (EBMUD). Note that EBMUD response time for flow testing requests can be up to “15 business days.”

Low water pressure in a home could also be caused by a water leak. A leak detection contractor can conduct testing and even locate the source of the leak. If a leak is found, you’ll need to hire a plumbing company like Pipe Spy to repair or replace the damaged water lines.

More Questions about Low-Flow Toilets?

If you’re still looking for answers, our team of plumbing experts is always glad to help. Contact us any time at 510-465-3000.