Bluelab white and blue digital pH pen with LCD screen displaying 5.9 pH and 20°C, shown against a white background.

Bluelab pH Pen, Waterproof

$67.97
$67.97 $99.95
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Bluelab white and blue digital pH pen with LCD screen displaying 5.9 pH and 20°C, shown against a white background.
  • Bluelab white and blue digital pH pen with LCD screen displaying 5.9 pH and 20°C, shown against a white background.
  • White and blue digital pH pen with a digital display showing 5.7 and 20C, including a cap and blue lanyard.
  • Two digital pH pens in white and blue, each in a small cup of test liquid and featuring an LCD screen and lanyard.
  • Handheld Bluelab pH pen displaying a 5.7 reading, submerged in dark, rippling water.
  • Bluelab white and blue digital pH pen with LCD screen displaying 5.9 pH and 20°C, shown against a white background.
  • White and blue digital pH pen with a digital display showing 5.7 and 20C, including a cap and blue lanyard.
  • Two digital pH pens in white and blue, each in a small cup of test liquid and featuring an LCD screen and lanyard.
  • Handheld Bluelab pH pen displaying a 5.7 reading, submerged in dark, rippling water.
Bluelab pH Pen, Waterproof

Bluelab pH Pen, Waterproof

$67.97
$67.97 $99.95

Know your pH in seconds with a pen that thrives in the grow room

The Bluelab pH Pen reads pH from 0.0 to 14.0 at 0.1 resolution and shows solution temperature on the same backlit screen. It is fully waterproof (not just splash-resistant) and floats if it lands in your reservoir. Bluelab builds it in New Zealand with a double-junction probe for longer life in nutrient-heavy solutions, and it ships with pH 4.0, pH 7.0, and KCl storage solution so you can calibrate and start measuring the same day.

Fully waterproof 1-year warranty Made in New Zealand
Free shipping on orders over $49
30-day returns on all orders
Serving growers since 2006
Gallery
See it in action
Side by side
Cheap pH pens vs. the Bluelab pH Pen
Budget pH pens
  • Single-junction probes clog fast in nutrient solutions
  • Drift out of calibration within days
  • Water-resistant at best, dead after one drop in the reservoir
  • No calibration reminder, so you forget and run on bad data
  • No temperature compensation, readings shift with heat
  • Calibration solutions sold separately, adding $10+ on day one
Bluelab pH Pen
  • Double-junction probe resists contamination from nutrients
  • 2-point calibration (pH 4.0 and 7.0) holds accuracy to ±0.1 pH
  • Fully waterproof and floats, built for daily reservoir use
  • 30-day calibration reminder built into the firmware
  • Automatic temperature compensation adjusts readings in real time
  • pH 4.0, pH 7.0, and KCl storage solution included in the box
Key features
What makes this pen worth keeping

Double-junction pH probe ±0.1 pH

Two reference junctions instead of one. The outer junction takes the beating from nutrient salts so the inner junction stays clean, which means stable readings for longer before the probe wears out.

Waterproof and floats

Not splash-rated, fully waterproof. If it slips into the reservoir, it floats on the surface instead of sinking to the bottom.

Automatic temperature compensation

pH readings shift with temperature. The pen measures solution temp (0 to 50°C) and corrects the pH value automatically, so a reading from a warm reservoir is just as reliable as one from a cool mixing bucket.

Backlit LCD with hold function

The screen lights up for reading in dim grow rooms. Press the hold button to lock the display so you can pull the pen out and read at eye level.

30-day calibration reminder

A built-in timer tracks the days since your last calibration and alerts you when it is time to recalibrate. No guessing, no forgetting.

Auto-off and low battery warning

The pen shuts itself off after inactivity to preserve the single AAA battery. A low-battery icon appears before it dies so you are never caught mid-reading.

Specs
Technical details
pH Range
0.0 to 14.0 pH
Accuracy
±0.1 pH (at 25°C)
Temp Range
0 to 50°C / 32 to 122°F
Resolution
0.1 pH, 1°C / 1°F
Calibration
2-point (pH 7.0 and pH 4.0)
Power
1x AAA alkaline (included)
Origin
Designed and built in New Zealand
Warranty
1-year limited (proof of purchase required)

How to set up and use your pH Pen

1

Hydrate the probe

Remove the storage cap and soak the probe tip in the included KCl storage solution for 24 hours before first use. This activates the glass membrane so it can read pH accurately.

2

Calibrate with two solutions

Dip the probe in the pH 7.0 sachet, press the calibration button, then repeat in the pH 4.0 sachet. A confirmation indicator on screen tells you the calibration succeeded.

3

Take your reading

Submerge the probe in your nutrient solution or reservoir and wait for the display to stabilize. The reading shows pH and temperature simultaneously on the backlit screen.

4

Rinse, store, repeat

After each use, rinse the probe tip in clean water, then replace the storage cap with a few drops of KCl solution inside. This keeps the probe hydrated and extends its working life.

In the box
Everything you need to calibrate and start measuring
Included with every pen
  • Bluelab pH Pen (waterproof)
  • pH 7.0 calibration solution sachet
  • pH 4.0 calibration solution sachet
  • KCl probe storage solution
  • 1x AAA battery (installed)
  • Quick-start guide
Recommended add-ons
  • Bluelab PPM Pen: Measures EC/PPM so you can check nutrient strength alongside pH
  • Bluelab Probe Care Kit (pH): Extra calibration sachets, KCl solution, and cleaning tools for ongoing maintenance
  • Bluelab KCl Storage Solution (250ml): Larger bottle for long-term probe storage between uses
Not sure if you need the Conductivity Pen too? If you are hand-mixing nutrients, yes. pH tells you whether plants can access food, EC tells you how much food is there. Call us and we can walk you through it: 716-217-0353 / help@happyhydro.com
Questions
Frequently asked questions
The only setup is hydrating the probe in KCl solution for 24 hours (comes in the box), then doing a two-button calibration with the included pH 4.0 and 7.0 sachets. The pen shows a confirmation icon when calibration is successful, so you know you did it right. After that, you just dip and read.
This pen is designed for testing liquid solutions: reservoirs, runoff, tap water, or nutrient mixes. If you need to test directly in soil, coco, or other solid media, Bluelab makes a separate Soil pH Pen with a flat-tip probe designed for that. This standard pH Pen is the right choice if you are checking water or nutrient solution before you pour it.
Bluelab recommends calibrating once every 30 days, and the pen has a built-in reminder that tracks it for you. Each calibration takes about two minutes. You will eventually run out of the included sachets, so picking up a Bluelab Probe Care Kit or extra sachets is a good idea for the long run.
The probe on the standard pH Pen is not replaceable. With proper care (rinsing after use, storing in KCl solution, recalibrating monthly), most growers get 1 to 2 years of reliable use. If you want a replaceable-probe option, Bluelab recently released the pH PenPlus, which accepts a swap-in probe when the original wears out.
Yes. The probe tip is a glass membrane that must stay hydrated to read accurately. If the probe dries out, readings drift and eventually the probe fails permanently. Add a few drops of KCl solution inside the storage cap and keep it on the pen between uses. Never store the probe dry or in plain water.
The Bluelab pH Pen reads to 0.1 pH resolution with ±0.1 accuracy at 25°C. For hydroponic nutrient management, where your target range is typically 5.5 to 6.5, that level of precision is more than enough. Lab-grade meters read to 0.01 pH, but that extra decimal point rarely changes a grower's decision.
If you receive a defective or damaged unit, email us a photo at help@happyhydro.com and we'll make it right immediately: replacement or refund, your call. For change-of-mind returns, we accept returns within 30 days for items in new, resalable condition. If you're not sure whether this product is right for your setup, call us first at 716-217-0353. We'd rather answer your questions before you order.
Happy Hydro has been selling growing equipment since 2006. We've carried Bluelab for years because the systems work great and customers who buy them leave happy. Have questions before you order? Call 716-217-0353 or email help@happyhydro.com. We're easy to reach and happy to help!

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