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Based on the conditions at your local weather station, Zilker calculates the amount of evapotranspiration (ET) that occurs. Using a widely accepted formula standardized by the American Society of Civil Engineers (ASCE), Zilker calculates ET based on temperature, humidity, cloud coverage, and other factors.

The water in your soil can be thought of as money in a bank account. ET acts as a withdrawal from the account. Irrigation and rainfall act as deposits.

Zilker monitors your account, and waters only when the water drops below a certain threshold.

Watering only when needed makes the most efficient use of water. And it results in healthier plants with deeper roots, too.

If you choose, Zilker can ignore the weather and water on a pre-determined schedule.

Just go to and add your station. Then select the new station from within the Zilker app.

How it works

Communication is relayed from your iOS device to your valves via the Zilker Cloud and the Zilker Bridge.

If your Internet service is interrupted while a watering cycle is in progress, the watering cycle will continue and end as usual.

New watering cycles will not be initiated until Internet service is restored.

An axial turbine inside Zilker measures flow rate. Along with the area covered by a sprinkler or drip hose, Zilker can calculate the inches of water applied to that area.

So, for example, you can ask Zilker to apply 1” of water to your lawn.

If your hose develops a leak, flow rate can increase significantly. Zilker continuously monitors flow rate, and will alert you if a significant increase occurs.

Zilker uses a 900MHz radio (between the bridge and each valve). These radios have roughly 2.5 times the range of Wi-Fi and are better at penetrating obstacles such as interior and exterior walls.

With direct line of sight, a valve and the bridge can communicate at distances of up to 500ft.

You can get additional range by cleverly positioning the Zilker Bridge within your home. For instance, if you have valves in both the front and backyard, you can place your Zilker bridge halfway between the two sets of valves.

Under most conditions, your batteries will last a year or more. However, depending on your specific use-case, your battery life may be longer or shorter.

Zilker can water once per day for 10 minutes for 18 months when using 2500mAh alkaline batteries.

Any type of AA battery is acceptable except Nickel Metal Hydride (NiMH). NiMH batteries do not supply the proper voltage for Zilker.

If you would like to use rechargeable batteries, we recommend Lithium Ion rechargeables.

• Internet service and a Wi-Fi network
• An iOS device with iOS 10 or later
• Two AA batteries

Unfortunately no, not at this time. You can sign up to the mailing list to get notified when it is available.


Zilker is a bit too wide to fit side-by-side on some manifolds. Many manifolds have a pitch of 50mm; Zilker is 56mm wide.

We recommend a particular manifold that fits three Zilker Valves perfectly. See Figure 1.

• Manufacturer - Orbit Irrigation
• Model Number 62009
• Amazon ASIN B000PSFLT2.

If you prefer a brass manifold, a widely available four-way style will fit three Zilker Valves as well. Valves will not fit side-by-side in the center positions, but there is room for one valve and an extra hose. See Figure 2.

Y-splitters work well for two Zilker Valves. See Figure 3.


Zilker can be directly sprayed with a hose, but it cannot be submerged in water.

There are four small weep holes on the bottom of Zilker (see Figure 1). If water manages to collect inside Zilker, it will drain away through these holes, allowing Zilker to continue operation.

Zilker should not be installed in a position that allows water to enter the weep holes. So Zilker should not be laid flat where a puddle may form, for instance. And it should not be installed upside down.

Fig.1 - Weep holes

Zilker requires at least 15 PSI in order to activate the internal mechanism. Therefore your rain barrel must be equipped with a pump for Zilker to function properly.

No, Zilker should be brought indoors during freezing temperatures. The Zilker app will alert you when freezing weather is approaching.

It’s possible there is a backflow preventer installed on your faucet. If so, the backflow preventer will interfere with the wire mesh gasket supplied with Zilker, preventing installation. See Figure 1.

Fig.1 - A typical backflow preventer installed on a faucet

If a backflow preventer is installed, there’s a good chance you'll be unable to remove it. Some have been welded in place; others are corroded in place.

We recommend swapping the gasket with wire mesh (supplied with Zilker) for a gasket without wire mesh. See Figure 2. There’s no need to go to the store; your garden hose already has a gasket without wire mesh. Just swap them.

Zilker will lose the benefit of the wire mesh screen. But unless your water frequently contains large particles of debris, Zilker will function normally.
Fig.2 - Gaskets with and without wire mesh

Zilker is certified for use in the USA, Canada, Australia, and New Zealand.

The store at will only accept orders from addresses in the continental US.

If your address is outside the continental US, please order at

Unopened and unused products may be returned for a full refund within 30 days of purchase.

Yes. Zilker is warranted for one year from the date of purchase against manufacturing defects. Austin Devices will repair or replace warranted units (at our option). Austin Devices is not liable for damage caused by freezing water or other misuse.

All orders include free 2-day shipping.

  • Most orders ship the same day, but please allow up to two business days for your order to leave the warehouse.
  • You will receive an email with your tracking number when your order is shipped.
  • Some carriers do not deliver on Saturday or Sunday.

From Zilker Metropolitan Park, the central park in our hometown, Austin.

Yes, US patent US9049821 B1.