How to Save Water With a Low Flow Toilet - Dengarden - Home and Garden
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How to Save Water With a Low Flow Toilet

With a master's in sustainable development, Susette helps Southern California water agencies carry out their water conservation projects.

Owners of older homes often don't realize that their fixtures, irrigation, and energy systems might be costing them a whole lot more than is necessary. For example, older toilets—those installed before 1992—use anywhere from 3.5 to 7 or 8 gallons of water each time they flush. The new ones, with updated technology, use only 1.28 gallons. That's a huge difference! Not only is that extra water essentially wasted, but you're also paying more on your water bills than you need to. Here's the skinny about toilets.

Tank-Type Toilet

Tank-Type Toilet

Flush-Valve Toilet

Flush-Valve Toilet

Old Toilets versus High Efficiency Toilets

When water suppliers ran studies about water use in the home, they discovered that toilets alone were using almost as much water as what you'd use to irrigate a medium size landscape! They decided to help their customers save water by providing new, more efficient toilets, like the ones manufacturers were making that used 1.6 gallons per flush (gpf)—called ULFT's or Ultra-Low Flush Toilets.

As happens with all new inventions, some things about them worked and others didn't. Most of what didn't was related to how the flush was handled by the existing piping system that carried it away. The flush needed more push. In response to customer feedback, manufacturers redesigned them to use only 1.28 gpf, but with a higher velocity flush. These worked a lot better than the original ULFTs.

Then manufacturers saved even more water by creating dual flush HETs that had a light flush and a heavy flush. The light flush uses only 0.8 gpf and is used for flushing liquids. The heavy flush is for solids. Water suppliers, after testing the new ones for efficiency, started providing this kind of toilet to customers for free.

Toilet Distribution Event

Have you ever seen a toilet distribution event? Several years ago I worked for Waterwise Consulting Inc., a small consultancy that carried out conservation programs for California water suppliers. One of their most successful projects was setting up distributions of new High Efficiency Toilets (HET) free to the public.

For these events we would negotiate a contract to buy 500–1,000 new toilets (usually with a company called Niagara), schedule an event, then contact a water supplier's customers and invite them to come and pick up a freebie. They had to agree to bring their old toilets back, as soon as they'd installed the new ones, and we would recycle it for them. The water supplier paid us based on the number of toilets distributed.

Then I supervised another contract with a big water wholesaler where we went into hotels to see how they used water, and helped them figure out ways to save. I discovered that toilets used more water than any other function inside a house or hotel.

For a number of years water suppliers offered toilets, shower heads, and other water-using fixtures free of charge to their customers. Some of them still do offer water use surveys, so you might want to check the website of your supplier, if you want to know how you're using water and if you could use less. Meanwhile, let's look at toilets to see how they work and why you save with the newer ones.

Waterwise Consulting used to recycle all these old toilets, as soon as customers brought them in—usually a week or so after they picked up their new ones at the distribution event.

Waterwise Consulting used to recycle all these old toilets, as soon as customers brought them in—usually a week or so after they picked up their new ones at the distribution event.

Main Types of Toilets in the United States

In the United States there are two main types of HETs—the tank type and the flush-valve type (see photos above). The tank type is what is installed in most homes. It uses gravity to move water from the tank down to the bowl and out with each flush. It generally has a less effective flush than the flush-valve type.

Flush-valve toilets are used primarily in commercial buildings, like hotels and gyms, where the supply pipe diameter is larger. Flush valve toilets do not have a tank to store water. Instead the water comes directly from the main pipes every time someone flushes. This guarantees built-in pressure. Flush-valve toilets are more effective and normally cost more than the tank types.

Savings With a Low Water-UseToilet

Consider this: With a single user at home, if you flush a 3.5 gpf toilet five times a day you are using almost 18 gallons of water. If you flush a 1.28 gpf toilet five times a day, you use just over 6 gallons. That's a big difference—almost 2/3 less water with the newer one!

Per month that would mean 540 gallons for the old one compared to 180 gallons per person for the more efficient one. If you include flushes for cleaning the toilet, you use more. If you have more than one person in your household or business, you use much more. Check out the following chart:

# of Flushes per DayOld 3.5 gpf ToiletNewer 1.28 gpf Toilet

5 (single person staying at home)

17.5 gallons/day

6.4 gallons/day

12 (3 people with one working)

42.0 gallons/day

15.4 gallons/day

15 (3 people all at home, or 5 people with 2 working outside)

52.5 gallons/day

19.2 gallons/day

Now imagine your house or company, plus each person in your part of town using that much water, and you can see where using a lower flush toilet can contribute a lot toward reducing the amount of water needed from municipal water systems.

Here is a calculator to use, if you are curious to know how much water your toilet and other bathroom fixtures are actually using: Water Consumption Calculator

Estimating the Return on Investment (REI)

An easy way to decide if a conservation purchase is worth making is to see how long it would take to repay its cost with the money you save. If you get your toilet for free, then of course its worth it, especially if you can install it yourself.

If not, you would estimate how much you use your old toilet (number of gallons) per year, figure the number of gallons you would use with a more efficient one, and subtract to get the gallons saved (like we did above). Then multiply the gallons saved by the cost of water and sewer to show how much money you could save on your water bill.

Once you have your potential savings, calculate how much it will cost to buy and install the new toilet. Divide that figure by how much you could save. This will show you your REI (Return on Investment), i.e. how long it will take savings to pay back the installation. Once you've paid back your costs, that is when you really start saving.

The formula: Purchase cost + installation cost / dollar savings = Simple payback time. Everything after that is gravy . . . or you could use your savings to finance another water-saving purchase.

Niagara is a Top-Notch Brand

Getting Rid of Your Old Toilet

This can be tricky! You will need to look for a recycling company—one that collects, if you are replacing a high number of toilets. Call your water provider or plumber to see if they know of a recycler. Your city or trash pickup company might also be able to help.

Another option is to keep the old toilet, clean out its innards, and turn it into a dual-level planter for flowers or ferns. You can paint the enamel outside for additional decoration. See this site for how to adapt your old toilet to a Potty-O-Planter: Potty-O Planter

Latest Technology in Toilets

The most modern type of toilet you can buy today is actually a no-flow toilet. This kind of toilet does not use water at all or if it does use water, it's just a tiny bit to clean the bowl with. The bad smells we all associate with toilet use actually come from mixing urine with the hard wastes, so this kind of toilet separates them from the get-go. Solids go down one way and, mixed with a dry soil enhancer, actually become compost. Urine goes down another way, is mixed with greywater, and used as a liquid fertilizer for the landscape. Depending on the country, this kind of toilet is called a waterless toilet, a dry toilet, or a compost toilet. There are many different varieties on the market.

Other countries have designed toilets that use water in different ways:

  • A popular one, that does NOT save water, is the French bidet—which allows you to wash, instead of wipe after evacuating.
  • Vacuum-assisted toilets use a vacuum to suck waste out of the bowl from below. They use hardly any water and are very quiet The Niagara toilet shown above is a vacuum assist one.
  • There's a European toilet that has a skinny, high tank that uses gravity to rush water into the bowl, thereby rinsing with greater speed and efficiency.
  • Japanese toilets have a little hand washing sink above the tank that fills the toilet with runoff from your hands. This saves a lot of water.
  • Then there's the latest contest in innovative toilet technologies, that will hopefully also help with providing clean sanitation for third world countries. This Reinvented Toilet Expo was set up by Bill Gates in Beijing (2018), which he says advanced toilet technology by 200 years.
Japan has a unique toilet of its own that saves even more water than do the U.S. low-flow toilets.

Japan has a unique toilet of its own that saves even more water than do the U.S. low-flow toilets.

Treat your current toilet well.

In the meantime, until you do replace your current toilet with a more efficient one, be sure to treat it well. Keep it clean. Don't use harsh chemicals or brushes that could erode the surface. Don't put anything in it that doesn't easily break down in water. And while you're becoming more efficient, think of other ways you can conserve water too. Above all, if your toilet runs, stop it right away. Running toilets can waste a lot of water.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.


Susette Horspool (author) from Pasadena CA on January 28, 2012:

mljdgulley354 - Vinegar is a good cleaner. For anything that needs scraping I use baking soda. In fact, I don't use any cleaners other than baking soda and natural detergents for clothes and dishes.

cclitgirl - Many states in the US have made it law that, after a certain year, stores cannot sell toilets that are not HETs. Meanwhile, inventors are coming up with more and more interesting toilets, including one that sends liquids out one way and solids out another. Maybe I'll write a hub on that.

Cynthia Calhoun from Western NC on January 28, 2012:

I LOVE this - I should say I love the idea of saving water and money. I almost think it should be the law that all new commodes are HET. Water is not an unlimited resource, and the more we ALL save, the better.

mljdgulley354 on January 28, 2012:

I am all for saving money. When we bought our house the toilet in the master bedroom was cracked so we had to replace it. We bought our new one from Lowe's and the first thing my husband looked at was how efficient it would be in the use of water. In cleaning I prefer using vinegar rather than harsh chemicals. This was a very informative article. Thank you for sharing