Front Row Ag · pH Up Calculator

pH Up Calculator

⚠

Why Each Recipe Has a pH Ceiling

⚠ Above a certain pH, calcium phosphate starts falling out of solution — that's the scale that clogs lines and emitters and can kill plants. Where that line sits depends on the recipe and EC: flower recipes carry 3–4× the phosphate of Veg, so at high-strength ECs they meet the line around pH 5.7–5.8 while Veg still has room at 5.9. Each row below shows its own ceiling and defaults to a target 0.1 below it (never above 5.9). If you need more pH Up than the row recommends, don't push the target up — check your meter calibration, measure at the dripper, and contact your Sales Rep or Retailer.

ⓘ

pH Measurement Tips

Calibrate your meter the same day (pH 4.0 and 7.0 buffers), then measure at the dripper or in the batch/bay tank. It is EXPECTED and NORMAL for pH readings to be LOW at the fertigation skid—especially in high flow situations. If testing in a batch tank, allow at least 10-15 minutes between pH adjustment and checking values — and note that a fresh tank on alkaline source water reads 0.2-0.3 lower than the lines will, because dissolved CO2 hasn't gassed off yet.

About This Calculator

This calculator recommends a target pH per recipe and the pH Up dose that reaches it. Doses are built on regression equations from 131 real-world trial data points; targets come from a chemistry model of the FRA recipes that finds the pH where calcium phosphate starts forming at your EC. Each row defaults to 0.1 below that ceiling (never above 5.9) — you can edit the target, and the row will warn you if you set it at or over the line.

Important: doses assume RO water. If your source water has alkalinity (tap or well water), enter it above — every 19 ppm of alkalinity (as CaCO3) supplies the same base as 0.1 g/gal of pH Up, and the calculator subtracts it. Water above roughly 40 ppm needs no pH Up at all at flower ECs; more than that and you're into pH Down territory (see the pH Down calculator).

Features:

Preset buttons: Quick-fill for High Strength or Standard feed chart ECs, or enter custom values.
Output formats: View results in g/gal, mL/gal, or % injection rate.
Share Link: The URL updates as you make changes—copy and send to share your exact configuration.
Copy Summary: Get a formatted text version of your settings and recommendations.

For commercial and home growers alike, whether mixing direct to reservoir or running stock concentrate through an injection system.

💧

RO Water & Alkalinity Creep

As RO membranes age and approach their replacement threshold, they allow more carbonate and alkalinity to pass through. This gradually raises the natural buffering capacity of your source water — a phenomenon called alkalinity creep.

The practical effect: your pH Up demand drops over time without any change to your feed recipe. If you notice you're using less pH Up than usual, your membranes may be degrading.

What to do: Don't change your pH target — the right target depends on the recipe and EC, not the water. Instead, measure your permeate's alkalinity (a simple KH drop kit works) and enter it in the source-water field above; the calculator subtracts what the water now supplies. When membranes are replaced, alkalinity drops back to zero and pH Up demand returns to baseline — re-measure and update the field.

How are you mixing Front Row pH Up?

Direct to Reservoir: You're adding pH Up powder directly to your batch tank or reservoir at working strength. The calculator tells you exactly how many grams to add based on your reservoir size.

Stock Concentrate: You've pre-mixed pH Up into a concentrated stock solution that gets injected by dosing equipment. The calculator shows your injection rate (mL/gal or %) based on your stock concentration. Choose the preset that matches your injector, or enter a custom concentration.

Reservoir size: gallons

20 g/gal stock concentrate (D14MZ2 or similar)

100 g/gal stock concentrate (D14MZ3000 or similar)

Custom stock concentrate: g/gal

Source water alkalinity: ppm as CaCO3 (0 for RO) Lines run warm (>77 °F in the room)

Enter your target EC values for each recipe:

Recipe	EC	Target pH	g/gal	use this Total

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Technical Details

Doses are based on regression analysis of 131 trial data points measured to a final pH of 5.9 in RO water. Two adjustments sit on top of the regressions:

1. Per-recipe pH ceiling. The pH at which calcium phosphate reaches saturation for each recipe, from a chemistry model (PHREEQC speciation) of the FRA formulations validated against the same trial data (Aug 2026): ceiling = a − b×log10(EC) at typical room temperature, with Veg a=7.26/b=2.38, Stretch 6.69/1.92, Stack 6.63/1.88, Swell 6.55/1.85, Ripen 6.65/1.89 (±0.02 pH over EC 1.4–3.4). Warm lines (>77 °F) sit ~0.08 lower. Default row target = ceiling − 0.1, capped at 5.9.

2. Dose scaling by target pH. The dose to reach a target other than 5.9 is the regression value times a factor that is the same for all five recipes (±0.03): 5.5→0.43, 5.6→0.54, 5.7→0.67, 5.8→0.82, 5.9→1.00, 6.0→1.21 (interpolated between, capped at 6.0). A source-water alkalinity credit of 0.1 g/gal per 19 ppm (as CaCO3) is subtracted last, floored at zero.

Recipe	Model	Equation	R²	EC Range
Veg	Quadratic	`0.0076×EC² − 0.0042×EC + 0.0094`	0.965	1.50-3.50
Stretch	Linear	`0.0717×EC − 0.0434`	0.911	2.00-3.00
Stack	Linear	`0.0854×EC − 0.0655`	0.968	1.80-3.50
Swell	Quadratic	`0.0747×EC² − 0.263×EC + 0.3657`	0.986	2.00-3.00
Ripen	Linear	`0.1216×EC − 0.0914`	0.969	1.60-2.20

Regression Charts

Veg

Stretch

Stack

Swell

Ripen

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