Dual Flush Toilets - money saver or snake oil?
Today's Consumerist posted a link to a blog on how to install your own dual-flush toilet. I won't go into the specifics of it, but the dual flush system allows a little bit of water for certain flushes and a lot of water for other flushes. Here at UCAN, we're all for saving water, but the blog's claim was that not only did you save water, but you saved money. The projected savings? $100 a year. That seemed like a big price savings, but we wanted to know if San Diegans would see those types of costs savings.
It's fairly simple to figure out your cost savings. You take the number of gallons per flush with your old system multiplied by the amount of flushes per year to get your annual toilet water use. You then determine how much water your new flushing system uses per year and subtract. This is your water savings in gallons per year. Since the City of San Diego charges you by hundred cubic foot (HCF) of water, you need to convert gallons into HCF. There are 748.05 gallons per HCF. Whew! Maybe that wasn't so simple.
Here's a simplified model to see how much water you save. Let's say you live in a home with another person (two people total) that share a toilet. The toilet uses 3.5 gallons per flush. At an average of 10 flushes a day (5 for each person), the single flush toilet uses 12775 gallons per year.
The dual flush system touts that it can save up to 70% water per flush. That's probably half-marketing, half-truth, so we'll say that the dual flush system will save 50% water per flush. This means that instead of using 3.5 gallons per flush, the toilet will use 1.75 gallons per flush. The annual water use is cut in half, to 6387.5 gallons per year saved. That's a lot of water! But, how much does it actually save you?
6387.5 gallons of water is approximately 8.53 HCF. To find out your annual cost savings, we simply need to multiply the HCF saved by the City's charge per HCF.
Currently, the San Diego City Water Department has three tiers. In the first tier, water is $3.293 per HCF; the second tier is $3.571 per HCF; and the third tier is $4.009 per HCF. This means a two-person household flushing the toilet 10 times a day will save $28 per year in the first tier, $30 in the second tier, and $34 in the third tier.
While those eagle eyed readers will point out that these numbers are nowhere near $100 a year, this doesn't mean that certain people won't see those types of savings. A family of 4 could easily hit the $100 per year savings, and larger families would save even more money.
Additionally, the author of the blog purchased his dual-flush conversion kit for about $20. Even if you are only savings $28 a year, the kit will pay for itself fairly quickly.
Bottom line? Depending on your current toilet water use, you potentially could see a large drop in your annual water bill. However, if your toilet doesn't use that much water, your cost savings may be minimal. That being said, it is always great to conserve water. This little conversion kit may be enough to bump you down from a higher-priced tier to a lower-priced tier.
Questions about your water bill? Wondering why we didn't use any toilet humor in this blog? Give the Fraud Squad a call at (619) 696-6966.