How Many Gallons?

11 years ago

Hi, I'm new to owning a home after a whole life in apartments, and I've got a lawn watering question. I live in Zone 9 in California, and my first water bill arrived. It says that I used 16,400 gallons of water in July, which seemed incredibly high, but, having never owned a house, I had no way to see if this might be close to being correct. I went in to city hall, and the woman at reception kindly printed out my daily usage graph for me. Most of the month, I hardly used any water at all (I live alone), but on lawn watering days, I was using right around 850 gallons on the lawn each time.

I'm on a Hunter X-Core controller that's set to water four times a week. Here's the breakdown:

Zone A: 16 sprinkler heads that run for 12 minutes on the main part of the lawn

Zone B: 15 sprinkler heads that run for 12 minutes on the part of the lawn on the side of the sidewalk closest to the street and on a strip of grass on the other side of my driveway

Zone C: 21 drip lines that run for 17 minutes and are used to water the shrubs

The X-Core was programmed by who-knows-who (I'm assuming it was whomever put in the irrigation stuff), and I left it alone when I moved in. The last time that it watered the lawn, I stayed out there throughout the whole cycle, and I just can't see how I could be using 850 gallons in those 41 total minutes. There's no run-off except for a little bit that sprays out of the sprinklers closest to the street.

The back yard is barren (as, apparently, is a common practice in some places), and I had intended to plant fescue seed as soon as it was the right time of the year for doing so, but that would be an additional 2,084 square feet to have to water. The front yard is about 750 square feet, so I'm assuming that I'd be using 300% more water for the back yard alone, meaning that I'd be using around 3,400 gallons each time I watered the lawn/shrubs. Obviously, I'm not doing that, but here are my questions:

1) Is it really possible that my current irrigation program uses 850 gallons every time I water the lawn? I suspect that it can't be right, that the city's meters are not calibrated correctly, but I have no way of knowing.

2) If the consensus on here is that my usage seems artificially high, what's the next step?

3) Am I watering the lawn too often and/or for too long? I taught myself how to program the X-Core, so I know how to reduce the amount of days that I water and the duration of that watering if that's something that I need to do.

Thanks for any and all advice.

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Comments (5)

lehua49
11 years ago
MW,

You need to do a water audit. It can be done two different ways.

1. Find out your irrigation system's water pressure. Google the specifications for your sprinkler heads and look up the flow rate of the sprinkler per your system's water pressure(it varies). Multiply the sprinkler's flow rate by the time it runs times the number of sprinklers and that is the gallons output for that sprinkler type per that period. Now add all the different type of watering you have for that period and that is the total gallon water output for that period. Multiply that for the number of periods in your monthly water bills and that is your total gallons. Is is the theoretical design output of your system per bill period.

2. This can be done as a check to your system's design output. Place cups or cans throughout your irrigated yard that will not tip over when irrigated on(dig a little into the ground. The number is up to you, the more the more accurate the estimate. This also lets you know your coverage pattern of for your lawn(wet and dry spots). Irrigate your lawn enough the be able to measure the depth of water in the cups or cans (1/2 inch is good)(record the time duration). Not all cup depths will be the same. Make a map of the cups location on your lawn. On the map put the depth recorded from each cup. Do this routine at different time of day. You will see the part of your lawn that get too little water and areas that get too much. Now average all the depths in the cups. Convert that average depth to feet. Multiply the average foot depth by the area of your irrigated lawn in square feet. That cubic foot volume times 7.481 gallons per cubic feet will give you the gallons that fell for your test period of irrigation on your lawn. Extrapolate the test time period to your scheduled time period and that is the total gallonage that actually fell on your lawn. Multiply the schedule period to get the monthly billing period time and you have calculated the billing total gallons. The general rule for lawns is 1" depth of irrigation per week. Tall Fescue needs more water than other grasses especially in the hot weather. Drip irrigation is another matter entirely. Let us know what you find. JMHO Aloha
madtownwriter
Original Author
11 years ago
Wow, thanks for the comprehensive advice. One of the first things that I did when I saw my July usage was go out and buy a Rain Bird P2A Water Pressure Gauge, and I'm at 48 psi. I'm going to e-mail my builder and see if they keep track of what types of sprinkler heads they installed, but if not, is there a way to tell by looking at them?
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lehua49
11 years ago
MW,

Hopefully, you must be irrigating off your house faucet. 48 psi is a good pressure for your house water usage but not a little low for irrigation systems(60 psi). So you must not be using rotor heads. The sprinkler heads should have a brand logo on them and then Google the brand name and look at the pictures and see what looks like yours. It doesn't have to be exact, then look up the specification and read the flow rate corresponding to 48 psi. You probably need to look at the manufacturer's more detail resources to get the flow rate. It wasn't as easy as I thought. Example of nozzle specs is below.

http://store.rainbird.com/product/detail/nozzle_resources_009.aspx

Download the technical specifications for the nozzles.

JMHO GL Aloha
homr
11 years ago
850 gallons could easily be used during each cycle. You do not have to go through any complicated and lengthly procedure to get a rough and close idea.

if you have 16 heads and each head has a 2 gpm nozzle in it, just multiply 16 heads x 2 gallons a minute each x 12 minutes = 384 gallons. You have two zones like this, so you can see that you could already be approaching 800 gallons. You did not say weather they were spray heads or rotary heads. Find out the brand of head and then look at what size nozzle is in the shaft of the head. You can cross reference the nozzle size and its resultant gpm by going to the manufacturers charts. This will give you a rough idea.
A Padgett
4 years ago
Rule of thumb- 30 minutes equals 1500 gallons