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General Hydroponics pH 4.01 237mL

Price: $15.00 Loading Data
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General Hydroponics pH 4.01 Calibration Solution is used to adjust your pH meter using the highest quality reference solutions, allowing growers to calibrate many popular brands of PH, EC and TDS meters (NaCl scale or the 442 scale). Easy to use, just dip your electrode into a small amount of the buffer and adjust the meter to read 4.01. Do not reuse solution. Suitable for all makes and models of pH pens and meters. Each batch is carefully checked by General Hydroponics technicians to ensure that it is precisely calibrated and yields reliable readings every time they are used.

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Product details
Product Dimension: 20.32 x 20.32 x 15.24 cm
Shipping Weight: 1.25 Kg
SKU: 2005
Date first available: July 06 2017
Average customer review: 4.3 out of 5 stars 242 customer reviews
Bestsellers Rank: #26 in Measuring Device
Customer reviews

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Mike SC


Verified Purchase

April 11, 2013

not much to comment on, after all how exciting can a calibration solution be? I will use this to calibrate my pH meter about once per month and use it to measure the wort in homebrew. I have found that calculations from Bru'in Water are pretty accurate so just use this to confirm and to adjust for future predictions. Darker malts generally go a little lower than predicted and lighter malts a little higher. Since a lot of the mashing completes pretty rapidly, adjusting the wort after the fact is less useful.

Rhonda Traylor


Verified Purchase

August 06, 2016

my husband bought an electronic PH meter and to ensure that the meter is calibrated he bought the ph 4.0 and the ph 7.0 to test the meter for accuracy. this product is spot on and works great. he said that you should calibrate the meter every 3 or 4 uses.

Craig Anderson


Verified Purchase

June 16, 2014

I love GH, I mean, it's just quality stuff. I have been using this to calibrate my PH meter with no problems. Packaging was great, the lids were taped on to ensure that it didn't spill during shipping. Excellent quality and is as accurate as they come.

Karen Smith


Verified Purchase

July 12, 2016

If you use a PH meter for your greenhouse water, you'll need different calibration fluids to achieve the levels your plants need consistently. This is the stuff for the low end of the spectrum, 4.01 calibration fluid. It works simply and easily!



Verified Purchase

December 19, 2016

I use this to adjust my ph meter each time before
I use it becaus my ph meter goes wacky if it sits in a drawer too long. Once I added too much acid blend to my wine because I trusted that ph meter before getting this 4.01 solution

John Munoz


Verified Purchase

March 04, 2013

I use this product to calibrate my ph meter and would recommend it for those who are finnicky with what to use with their high-end ph meters. Has long shelf life for those who use their meters sparingly as well.



Verified Purchase

November 27, 2012

Although I've never used any other ph-calibration product, I have no comparison, but this stuff seems to work just fine..I couldn't bring myself to spend a whole lot on this item, so I chose this one.



Verified Purchase

February 14, 2015

Works like it should. Just make sure the pH tester you buy can do three digits 0.00 and not just two 0.0 because other wise it won't calibrate correctly.

I bought the wrong tester



Verified Purchase

Has many uses and all are useful ! Wonderful stuff ! Just wish I knew they sold a 2 pack with both for half cost.. :(

October 15, 2018

Saved my crop as my mere wasn’t off sit hank you! Loved it ! Is for PH meters and storage long term as well as can be used in small doses to ph water up or down if in a pintch ...

Dale Furno


Verified Purchase

September 09, 2013

if you take care of your ph meter, this amount of calibration solution should last you several years if not a lifetime. Don't get this stuff on your skin.

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