Soaker Hose Runtime Calculator

Thirty minutes at the faucet = good watering, right? Wrong. If you don’t treat irrigation like a math problem by considering factors such as water pressure, hose length, and even soil type, you’re likely to leave beds soaked in some spots and bone-dry in others. The tool at left will translate your hose specs (and other variables) into actual minutes of run time for any given bed dimension. No more guesswork; just full soil.

A sound estimate hinges on knowing how much water your plants require and how much your watering system will provide. To determine the volume needed to hit your goal in inches of water soaked into the soil, you first figure out a conversion factor. This factor is about.623 gallons per square foot of bed area when wetted at one inch of water. The tool assume a certain volume per inch of water depending on bed size. The rest of the equation rely on that value.

How to Water Your Garden Correctly

For example, if the bed were four feet wide by eight long; meaning it’s 32 square feet, you’d multiply that area by the soak depth you want to achieve. Voila! You know the volume you’re shooting for. To make things easy, calculator does all the multiplying for you. This lets you focus on whether a one-inch soak is better for seedlings or tomatoes set to fruit.

But then there’s the hose, the variable. Soaker hoses aren’t created equal. And none of them have much information about their discharge rate on their label. With the tool you can choose anything from high-output rubber lines to low-flow porous tubes. All types comes with a defined gallons per hour per foot rating at standard pressure.

But here’s where most plans go wrong: Rated output assumes best-case scenarios, which don’t exist in backyards very often. Elevation changes (if your bed is higher than your faucet) or friction inside the hose itself will cause your actual delivery to drop off as it travels farther from the spigot. Efficient irrigation depends heavily on regulating water pressure. Delicate porous tubing shouldn’t be used with too much pressure; it causes misting instead of soaking! That’s why most home setups operates under excessive pressure levels.

Enter the pressure here in the calculator after all regulators, etc., have been accounted for. Depending on the flow/pressure relationship, a reduction factor will be used by the calculator. For instance, if you’ve got a twenty-pound-per-square-inch-rated hose but a ten-pound-per-square-inch-rated regulator installed, you’re only going to get a fraction of the flow indicated on the hose. To account for that, the calculator reduces the total gallons per hour accordingly. You’ll see the estimated run time stay in line with your expectations instead of being too high. (Without this derating, your timer might show 40 min, so you think you’re applying an inch of water…but you’re really getting six-tenths of an inch.)

And then there’s the complication of head loss caused by long runs. When you stretch a two-hundred-foot-long hose around a big vegetable garden, the last foot will recieve fewer gallons per hour than the first. To account for this, the calculator use both the diameter and length of your feed hose. It factors in filters and fittings that impede flow, too.

Maybe you have tons of water available from your tap, but are forcing it up and over a hill, and then squeezing it through a little-diameter timer filter and downhill to a bed on your patio? The total adjusted flow the tool calculates takes those elevation changes into account. Its calculated run time is one that reflects what’s reaching the soil, not what’s coming out of the spigot.

Embedded within the interface are handy reference tables, too. These detail the performance (based off pressure) of various hose types. They let you determine instantly, for example, whether your existing arrangement will work or whether you have to split up some zones. You can see at a glance, for instance, whether a long flower border needs to be divided into two separate valve zones to maintain even distribution. That’s so you don’t make the typical error of having just one huge zone, which sprays well at the beginning and dries out the rest of the way along.

The key to watering well is adjusting the amount you supply based on how much is needed at the right moment. This tool turns a time-consuming hit-or-miss guessing game into something you can do repeatedly (plug in your actual pressure, hose type and number of beds), so your roots gets what they need without wasting a drop. Stop watching the clock and just do the math.

This makes for happier plants and a watering schedule that is easier to fit into your routine. It’s the difference between calculating and observing, which is always better in gardening. You should of used this sooner.