Dual Flush Toilets Save Money?

[HamMan]

Just thought I’d share some math for others who might be wondering the same question that I was – do “dual-flush” toilets save money? In short: No.

Cost of water: I pay $4.63 per cubic meter including sewage = $0.00463/L ($0.001223/gal)

Assumed usage: 4 regular flushes per day on a regular toilet, versus 1 “solid” flush and 3 “liquid” flushes per day on a dual-flush toilet. This is for my master bathroom so it normally is only used when getting ready in the morning and evening.

American Standard: I’ve had bad experiences with cheaper toilet brands so I consider these pretty minimal.
Model 1: American Standard Reliant 4.8 LPF Round Front Toilet ($138.00)
Normal flushes per day: 4 x 4.8L = 7008 L/year
Cost per year: $32.45

Model 2: American Standard Cadet 3 2-Piece 6.0 LPF Dual Flush ($268)
“Solid” flushes per day: 1 x 6L = 2190 L/year
“Liquid” flushes per day: 3 x 3.8L = 4161 L/year
Cost per year: $29.41 ($3.04 saving)
Payback period: 42.7 years (bad investment IMO)


Glacier Bay: Home Depot’s store brand. YMMV, personally I avoid them.
Model 1: GLACIER BAY Premier 2-piece 6.0 LPF Single Flush ($98)
Normal flushes per day: 4 x 6L = 8760 L/year
Cost per year: $40.56
   
Model 2: GLACIER BAY All-In-One 2-Piece Dual-Flush ($144)
“Solid” flushes per day: 1 x 6L = 2190 L/year
“Liquid” flushes per day: 3 x 4.1L = 4489.5 L/year
Cost per year: $30.93 ($9.63 saving)
Payback period: 4.7 years (maybe worth it if the toilet lasts this long)

In both of these cases I’d be wary of the more complicated dual-flush toilet lasting long enough to save money.
Why bother to do math like this? I was actually tempted to “invest” in the $268 American Standard dual-flush before now. Instead I’ll get the simpler Relient model now and save $130. Am I overthinking this? Almost certainly, but that's my style!

[nereo]

Savings on water is not the driving force behind dual-flush toilets.  as you noted in most municipalities water is so cheap that the ROI can be decades.

the real reason to use a dual-flush vs. traditional toilets is if you give a damn about the environment.
You could make (and others have made) similar calculations about using disposable plates vs. normal reusable ones, about the 'cost' of plastic straws (about as much as for the soda it displaces) etc.

tl;dr - it's not about the money.

full disclosure: i have dual flush toilets installed since 2012. My personal opinion is that all renos and new construction homes should install them as a matter of principle.

[diapasoun]

It is also important to note that not all of us live where water is cheap -- our water rates start at $0.0089/gallon, and go up from there; that's nearly 8x what you pay! Unsurprisingly, yes, dual flush toilets are extremely common where I live.

Although I agree generally with nereo here -- even if you don't live in a place with expensive water, there's still an environmental case for using minimal amounts of (fresh, clean, drinkable!!!) water to flush your toilet.

[pseudoyams]

I live in a rural area with well water and a holding tank for septic.  So we have no water bill but we pay about $400/yr to pump the holding tank (multiple pumps @$80 per pump).  We bought the dual flush toilets to try to reduce the water going into the holding tank so we could pump it less.  We got the Eljer brand toilets for both of our bathrooms.  I think they were fairly cheap at Menards.  We've had them for over 5 years now and they've been great.  No issues. I think it's something like 0.6 gal flush for "liquids" and 1.6g for "solids".  I don't have definite proof that they reduced the holding tank pumping at all but they've been good toilets.

Sent from my SM-T550 using Tapatalk

[bacchi]

I installed the $20 dual-flush kit from Big Box. It's worked fine in my low-flow toilet for years.

Professor Toilet doesn't like them,

http://www.professortoilet.com/2010/05/24/dual-flush-retrofit-kits-do-they-work/

but it's important to remember that using button #1 is for liquids and #2 works the same as the toilet did previously. Payback was less than a year.

[FiftyIsTheNewTwenty]

Spending hundreds to save less than a watering can's worth of water a day seems ridiculous.

[jpdx]

Thoughts on the Niagra Stealth Toilet? This is single flush but only .8 GPF and people seem to love it. However, it looks quite complicated inside and I wonder how reliable and easy to fix they are in the long term.

[tralfamadorian]

Not to be crude but isn't it easier (and very common in my area) not to flush for "liquids" more than 1x/day? No dual flush cost and uses less water than 3x dual flush as 0.5x water per flush.

[Syonyk]

Not to be crude but isn't it easier (and very common in my area) not to flush for "liquids" more than 1x/day? No dual flush cost and uses less water than 3x dual flush as 0.5x water per flush.

I think that's a septic system thing.  We don't flush liquids unless they've been sitting there for enough hours to start getting funky.

Also, if you really want to save water, install a waterless urinal next to the toilet.  Or just go pee outside.

[jpdx]

That's a good point. We follow the "if it's yellow, let it mellow" philosophy, and I worry that the high efficiency of a new toilet would encourage us do away with this practice and we'll wind up using more water than before.

[HamMan]

the real reason to use a dual-flush vs. traditional toilets is if you give a damn about the environment.

The point I am making is that a lot of the green technology around is sold to those who want to look green.   

Good discussion everyone.
To be clear, I'm definitely in favor of things I can do to reduce my environmental footprint. The thing that stands out to me here though is that the dual-flush toilet hardly makes a difference in water consumption. We're talking a 9% reduction for the American Standard. The main flaw that wasn't obvious before I started researching is that the dual-flush toilet actually uses more water than a single-flush for solid flushes (at least the models I looked at). This kills a lot of the savings.

I can see much more effective ways I could spend the money to reduce my footprint. My home's attic insulation is pathetic and has been on my to-do list for some time. For argument's sake if I were to replace all 4 toilets in my home with dual-flush toilets it would cost me $1072, and result in a 9% reduction in the toilet-related water consumption. Or for the same money I could blow my attic from R10 to R60 and see a much more dramatic improvement in my home heating costs and carbon footprint. The choice is obvious to me. And I need to get serious about that attic...

[Prairie Stash]

I can see much more effective ways I could spend the money to reduce my footprint. My home's attic insulation is pathetic and has been on my to-do list for some time. For argument's sake if I were to replace all 4 toilets in my home with dual-flush toilets it would cost me $1072, and result in a 9% reduction in the toilet-related water consumption. Or for the same money I could blow my attic from R10 to R60 and see a much more dramatic improvement in my home heating costs and carbon footprint. The choice is obvious to me. And I need to get serious about that attic...

Go R80, once you start the incremental cost isn't that much higher, do the math of course. However you'll never be able to reset up everything to go from R60 to R80.

Home heating and home cooling; people often forget the cooling part. Have you tried going in your attic in the summer?

On the toilet side, it wouldn't cost $1072 to replace all 4, you should only be replacing them if they're requiring replacement. Then the choice is the same as your example, otherwise replacing a functional toilet with a new one will rarely have good economics. The option of keeping the staus quo needs to be examined if you already have a functional toilet.

[jpdx]

I would move to another house with fewer than four bathrooms. ;)