Lower the Horsepower

Reality

Multi-family buildings (Condos, apartments, even dormitories) don’t use much water. There are two hours of peak usage in the morning, and another two hours in the evening. But everybody does not decide at the same time to use the toilets and showers, while the rest of the family is doing dishes and the laundry.

And offices are the same. Lots of fixtures, but they’re not used at the same time.


Low flow fixtures

Environmental consciousness is driving technology, which has produced low flow fixtures throughout our homes. These low flow toilets, showers, faucets, washing machines, dishwashers, etc. use much less water than 10-20 years ago. Even the glamorous master-bath with body-sprays and rain-heads are soon forgotten and seldom used.


Fixture Count Method

Historically, the fixtures were counted up, and a calculator and matrix used to determine usage. Based on the plumbing code, which is 10-20 years old, and can NOT keep up with technology:

For a 88 unit apartment, the estimated usage using fixture count is about 140gpm.


Towle Whitney Method

Years ago, Gould’s pumps (Xylem) published their graph curves which illustrate the estimated usage, based simply on the number of units in the building (page 2). As the number of units goes up, the average consumption per unit drops.

Using the Gould’s curve for a 88 unit apartment, the estimated usage is about 53gpm.


Conclusion

Do you want a 2Hp pump, or 5Hp? A smaller horsepower system is:
• less expensive to install
• less expensive to maintain
• less expensive to operate (lower energy consumption)

Towle Whitney has relied on the Gould’s curve technique for 10+ years, and never undersized a system. And we have enough confidence in our sizing that we’ll back it up with a guarantee!