Water-Saving Toilets – 6 Best Toilets for Saving Water

Cut your water use with a new water saving toilet or a retrofit kit

All toilets sold today are water saving toilets, at least compared to those sold in past decades. If you have an old toilet, you’ll definitely save water at home by replacing your old toilet with a new efficient toilet. And even if your toilet is relatively new, there are ways to cut its water use even further. Considering that up to 30% of household water use is for toilets, there’s a lot of opportunity on the table!

Take a look at these two toilets – one an old 7 gallon toilet tank from the 50’s or so (left), the other a new 1.5 gallon tank (right):

There are two amazing things about that 7 gallon tank on the left. First of all, that the engineers of the 1950’s or earlier who designed such tanks couldn’t figure out a way to flush down the toilet waste with any less than 7 whole gallons of water, while the new toilet on the right works fine with just over 1/5 as much water (for a flush of solids), and just over 1/10 as much water (for liquids and bathroom tissue only).

But even more amazing is the fact that the old toilet doesn’t actually work very well. My parents have one of these massive 7-gallon toilet tanks on their cottage boathouse toilet (there’s a full apartment above the two-sloop boathouse) and it sometimes has to be flushed two or three times to completely empty the bowl of … um … solids. The new toilet in our upstairs bathroom, on the other hand, does an excellent job on solids at 1.5 gallons, and on liquids only at less than half that.

Let’s look at the various types of water saving toilets and water saving toilet retrofit kits:

  • Current standard toilets
  • Low-flush toilets
  • Dual-flush toilets
  • Composting toilets
  • Simple toilet retrofits
  • Dual-flush toilet retrofits

Current standard toilets

There were plenty of 7 gallon toilets in North America in the 1940’s and early 1950’s, but by the late 1950’s most toilets were down to 5 gallon tanks. The maximum allowable flush capacity for a new toilet was lowered to 3.5 gallons in the 1980’s, then in 1992 it was further restricted to 1.6 gallons. So by today’s standards, all new toilets are water saving toilets compared to what was in use a generation ago – every toilet less than 15 years old should have a flush capacity of 1.6 gallons or less. (The flush capacity isn’t necessarily the same thing as the tank capacity, since water saving toilets can discharge only part of the tank during a flush; the extra capacity might be to increase the water pressure.)

A 1.6 gallon (6 liter) per flush toilet tank uses less than a quarter the water of an old 7 gallon (26 liter) tank, and yet as the photos show, the tanks on modern-day water saving toilets don’t look a quarter the size of their predecessors – more like half the size. There are a couple of reasons for this. First, the newer tank is tapered towards the front – wider behind, narrower at the front. Second, the newer tank is lined with a polystyrene tank liner. This insulates the water in the tank, which is often colder than the indoor air, so that you don’t get condensation on the outside walls of the tank.

Low-flush toilets

We’ve come a long way, baby – from 7 gallons down to 1.6 – but we can do better. That’s the idea behind the WaterSense partnership program between the EPA and US plumbing fixture manufacturers: finding ways to do even better than current standards.

WaterSense-qualified water saving toilets are the equivalent of ENERGY STAR water heaters – they have to to not only meet the current required standard, but beat it. WaterSense toilets have to use at least 20% less water than the current standard, which means they either support a dual-flush option (more below) or they are a single-flush that starts at 1.28 gallons per flush (that’s 4.83L for us metric folks).

The toilet you see below is a good example of a WaterSense certified toilet. Although it’s fairly pricey, it takes hardly any water at all to flush – a mere 1.1 gallons. That means that instead of being just 20% better than the standard, it’s 31% better. We should all try to support companies who show this level of efficiency innovation, by buying their products! A toilet like this, if flushed 5 times a day, will save almost 20,000 gallons over a 20-year lifetime!

Dual-flush toilets

There’s a simple attitude adjustment that can change all old toilets to water saving toilets: as the saying goes, “If it’s yellow, let it mellow; if it’s brown, flush it down”. Unfortunately, the mellow part can get pretty mellow (or, more accurately, pretty rank), but I know plenty of people who still practice this water saving toilets technique. Dual flush toilets are water saving toilets that give you the same savings without the unpleasant sights and smells.

Dual-flush water saving toilets have two flush capacities. The ‘liquids’ flush is for urine and small quantities of bathroom tissue, while the ‘solids’ flush is for the stuff that takes a little more water to coax down. Both flushes start from a full tank (so you get good water pressure); the liquids flush only uses part of the tank, typically 1 gallon, while the solids flush takes the usual 1.6 gallons. (The Ultra Low Flush toilet shown above takes 1.1 gallon for either flush, which is why they didn’t bother with dual-flush support on it.)

Dual flush toilets take a little getting used to in terms of figuring out where the flush handle is located and how to activate it. There are several versions of the flush mechanism. Some consist of a circular button on the top or side of the tank, with the circle bisected into smaller and larger halves (the small one being for the liquids only flush, of course), while others look like a standard flush lever but you have to push further down to get the full solids flush.

And of course, if you use the liquid-only flush on a dual-flush toilet you need to stop following the old adage. While the liquids-only flush is designed to work with liquids and bathroom tissues, it’s not designed to work with the accumulated bathroom tissue of half a dozen liquids-only uses (by the ladies).

Composting toilets

The simplest form of composting toilet is the good old outhouse or outdoor latrine. Composting toilets use no water and produce no sewage; instead they produce compost that you can spread on your garden. They are an extreme example of water saving toilets. There are two basic types of composting toilets: self-contained units, and composting toilet systems.

A self contained composting toilet consists of the toilet seat, bowl, and composting assembly all in one unfortunately very large package. These toilets (at least those available today) are so massive they are a bit of an eyesore, and on many the seat is so high up that the toilet comes with a step to get your bottom up there comfortably. Self-contained units may come with an electric agitator (to stir the composting sewage so it breaks down quickly), or a manual agitator (which means you have to remember to stir it periodically). Self-contained composting toilets are typically rated at 3-4 people, meaning the toilet can handle the toilet output of a household that size. If you have a lot of parties at your place, you might want to keep a regular toilet installed in the guest bathroom!

A composting toilet system has a toilet seat and bowl at one level of the house, and a composting tank that the toilet bowl drains into. This tank is usually on a lower floor, or at ground level in a side building if the toilet itself is on an elevated first floor. The composting tank usually has a considerably higher capacity than a self-contained unit, and can handle the output of more people. But of course that big tank eats up a lot of space.

Some issues with composting toilets that have prevented their adoption by more than extreme environmentalists or those with remote cabins lacking a septic bed, are as follows:

  • Odor: Composting toilets typically produce some degree of unpleasant odor.
  • Capacity limits: As mentioned above, composting toilets are limited in how much waste they can handle per day. And of course once the compost tray is filled up it needs to be emptied. Dumping out compost into the garden sounds relatively easy, but what about when it’s 20 below?
  • Agitation: The composting sewage in many composting toilets has to be agitated to keep it composting. As mentioned above some agitators are automatic, while others require you to do the stirring. This isn’t something most people want to think about, let alone do.
  • Appearance: As mentioned above, they look bulky. Of course, most regular toilets are ugly too, but they take up less of your field of view!
  • Energy use: A flush toilet uses almost no energy. Most composting toilets use electricity to heat the composting sewage, since it breaks down faster at high temperatures. Those with automatic agitation also use a tiny bit of electricity to do the agitation.
  • Cost: Composting toilets are very expensive. Starting prices are around the $1,500 mark for self-contained units, and in composting toilet systems the tank alone can cost that much.

If you are connected to a wastewater treatment system, you might be doing the environment some good by switching to a composting toilet, since you’ll use less water and put less of a burden on your municipal sewage plant. And if you’re trying to reduce your household water use to near zero, a composting toilet will help you meet that goal. But if your house is on a properly working septic system, there’s really no compelling reason to go for a composting toilet. You will save water, but it will probably take decades for the water savings to pay for the up front expense of the composting toilet. Consider investing in regular water saving toilets instead. The payback just isn’t there in most cases for composting toilets.

Simple toilet retrofits

The easiest retrofits for water saving toilets can be found at just about any home remodeling work site: bricks! For those really old 5- and 7-gallon tanks, you can make your toilet more efficient just by adding a couple of bricks to the tank. This keeps the water pressure high for the start of the flush (because the pressure is determined by the height of the water column, not the volume of water), and it reduces the volume of flush by the amount of water displaced by the brick.

Another retrofit for water saving toilets that was popular a while back was to install a toilet tank liner. You could buy a kit of polystyrene sheets, along with a special glue, and you would drain the tank, dry it thoroughly, and cut the polystyrene to size and glue it inside the tank. The main benefit was to insulate the tank walls from the cold water within, preventing condensation on the outside when it’s humid (as it often is in bathrooms). But it would also reduce the volume of water in the tank at least a little bit.

Unfortunately these kits, while still available today, are useless for modern water saving toilets. The styling on modern tanks involves lots of curves and unusual angles, and the amount of effort required to get the liner installed mean you are probably better off just to buy a new toilet, or at least a new tank with a liner pre-installed.

Fortunately, you can get a standard-flush toilet with a 1.6 gallon capacity for $100 or less today, and a WaterSense certified toilet for not too much more than that.

Your other option is to replace the tank of your existing toilet while keeping the bowl. Be careful doing this if the bowl is significantly older than the tank, because newer low-flush toilets accomplish their feat of getting more waste down with less water, through a combination of tank and bowl features. If the bowl is poorly designed, a newer tank and flushing mechanism will have trouble getting the bowl clean and you’ll wind up using two or three flushes to get those pesky skid marks off the bowl!

Dual-flush toilet retrofits

You can get the benefits of a dual-flush toilet without tearing out your existing toilet and installing a new dual flush unit. For considerably less money and effort, you can buy one of a number of different brands of dual flush conversion kit. These kits replace the existing flush mechanism inside your toilet tank, and once you install them and do a few test flushes to set the levels properly for the #1 and #2 flushes, you’re off and running. I installed one in my upstairs bathroom in an afternoon over a year ago, and it is still working fine. 

It’s more than the water you’ll save

When you switch to water saving toilets, you won’t just cut your household water use. You will also potentially cut your household energy use, especially if you have the heat on for part of the year.

Whenever your toilet tank fills up, the water in it tends to be colder than the ambient air of your house. As the tank water sits there, it soaks in the heat from its surroundings. When you flush, all that heat is flushed out with the tank water. The polystyrene insulation in the tank helps reduce this heat transfer, but insulation never stops heat transfer, it only slows it down.

In a typical new toilet of today’s vintage – meaning, a 6 liter or 1.6 gallon per flush model, you’ll lose the equivalent energy of a 40-watt light bulb burning for up to an hour – because of the warm water going down your drain, and the cold tap water coming in to take its place. An old 5 to 7 gallon tank will use several times that much. So replacing old, inefficient toilets with newer water saving toilets will not only save you a lot of water, it will cut your heating costs too.

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