Do Low Flow Toilets Cause Sewer Problems?

Low-flow toilets have become popular in recent years. As the name suggests, these toilets use less water—an important outcome that we encourage and practice ourselves here at Pipe Spy.  However, there are also a few downsides when it comes to the effects low flow toilet fixtures can have on plumbing systems. This is something you should keep in mind if you’re thinking about purchasing a low flow unit.

In this post, we will compare and contrast the benefits and the drawbacks of installing low flow toilets in a home or business. We’ll also provide tips on how to make your home as functional and sustainable as possible, whether you’re using low flow toilets or not.


The Pros and Cons of Installing 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 going green. The maximum gallons per flush allowed under US federal law is 1.6 gallons. Low flow toilets use 1.3-gallons of water per flush or less. There are also dual flush models, which typically allow for either a 1.3-gallon full flush or a 0.8-gallon reduced flush.


The primary benefits of low flow toilets include:

  • Water conservation. Sustainability is the primary motivation behind using a low-flush toilet as they use significantly less water than the full-flush counterparts. Over time, water-efficient toilets save thousands of gallons of water by limiting the amount used during each flush.
  • Cost savings. By using less water, your monthly water bill could be significant;y reduced. According to the EPA WaterSense website, families can reduce water used by toilets by 20-60% by using WaterSense labeled products such as low-flow toilets. These devices can save “more than $110 per year in water costs, and $2,200 over the lifetime of the toilets.”
  • Space savings. Since they hold less water, low-flow toilet tanks can help home designers who need to fit a tank in a smaller space. The difference in size may be relatively small, but every inch counts in tight spaces.


The major drawback with a low flow toilet comes with moving solids out to the sewer main. The low water volume in a low-flush fixture can make this challenging, leading to problems like clogging and bad 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. 

Low Flow Toilet Troubleshooting Tips

If you are experiencing water pressure issues during flushes, there are a few things you can do to fix the problem and prevent future issues.

The most important troubleshooting tip for low-flush toilets is to avoid flushing non-waste or toilet paper items. Do not flush wipes, paper towels, or anything else that isn’t supposed to be flushed. This should be said of all toilets, but is especially important for low-flow product owners who want to avoid the hassle of a clogged drain.

It’s also important to realize that low water pressure could be due to your home’s overall water pressure, which is regulated by the water service district. Homes in the San Francisco Bay area are likely to have a pressure reducing valve on the incoming water line to keep house pressure below 80 pounds per square inch (PSI). If the home’s overall water pressure is a problem, installing a supplemental booster pump may an option. This will be similar to pumps used in well systems and can increase water flow throughout the home. Consult a qualified plumbing contractor before making any modifications to your water service.

Before purchasing a booster pump, East San Francisco Bay and Oakland homeowners as well as commercial property owners should report water pressure problems and/or request flow and pressure testing from the East Bay Municipal Utility District (EBMUD). Note that flow testing requests are responded to “in 15 business days.”

Low water pressure in a home could also be caused by a water leak. This must be tested by a leak detection contractor. If you find that a leak is present, a plumbing company like Pipe Spy should be contracted to repair or replace the damaged water lines.

Need More Help?

If you’re still looking for answers, our team of plumbing experts is always glad to help. If we can’t answer your questions directly, we’re happy to refer you to another trusted resource.

Please feel free to contact us at 510.465.3000.