what kind of batteries does this use?

303/357 Battery - SR44 - Silver oxide 190 mAhModel 357A

What are the recommended and maximum flow rates? PSI?

FROM HM DIGITAL: There are no recommended flow rates, but there is a maximum pressure rating, which is 232 PSI (16 bar) at room temperature (25C/77F).

Can this be dropped into a DWC 5 gallon bucket and left in there so to measure the ppm's anytime i turn it on (since wire is sitting in the water) ?

It should not be fully submerged, only the probe up to the threads should go into liquid. You could probably seal wire end with a conformant coating or silicone though, do NOT get any on probe end. Yes it can be used in a deep water or reservoir, it does need to have some type of consistent flow in the probe area... to give a consistent reading ! ...get it naysayers, please think before you post inaccurate advice. A basic bubbler agitating solution will work. Be sure to locate probe out of direct bubble area , the bubbles will skew results. I've also used these in unagitated tanks , they work...but will only read the general area , obviously. This will give a general, consistent, read for on the fly observations of nutrient solution, but you still need to compare with a true reading for accuracy. TLDR Dont fully trust this as your standard when used for hydro, DO use as a consistent observation guide,check occasionally against a REAL meter/test, and keep it out of bubbles or it'll get wonky readings.

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HM Digital DM-1 In-Line Dual TDS Monitor, 0-9990 ppm Range, +/- 2% Readout Accuracy,Blue & White

Product ID: 2742434

Details

Brand
HM Digital
Item Weight
1.6 ounces
Item dimensions L x W x H
1.9 x 0.8 x 3
Material
Plastic
Number of Items
1

🎯+/- 2% readout accuracy

💧0-9990 ppm TDS range

🔗Dual in-line sensor setup

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Description

💧 Know your water, own your health — precision purity at a glance!

RELIABLE ACCURACY - Advanced microprocessor technology ensures readings within ±2%, so you trust every drop.
EFFORTLESS INTEGRATION - Includes quick-connect T-fittings and batteries for seamless installation under sinks or in coolers.
OPTIMIZE YOUR FILTRATION - Instantly verify your system’s rejection rate and never second-guess your water purity again.
ULTRA WIDE DETECTION RANGE - Tracks TDS levels from 0 to 9990 ppm, covering everything from pure to heavily mineralized water.
PRECISION WATER QUALITY INSIGHT - Dual sensors measure tap and purified water simultaneously for real-time filtration performance.

The HM Digital DM-1 In-Line Dual TDS Monitor offers professional-grade water quality monitoring with dual sensors that measure total dissolved solids (TDS) before and after filtration. Featuring a broad 0-9990 ppm range and ±2% accuracy, it provides instant, reliable data to optimize reverse osmosis, deionization, and other purification systems. Compact and easy to install with included quick-connect fittings and batteries, it’s the essential tool for anyone serious about water purity.

Specifications

ASIN	B001EHAZGW
Best Sellers Rank	#48,598 in Patio, Lawn & Garden ( See Top 100 in Patio, Lawn & Garden ) #81 in Swimming Pool Water Test Kits
Brand Name	HM Digital
Customer Reviews	4.6 4.6 out of 5 stars (2,725)
Global Trade Identification Number	00891144000052
Included Components	Bag
Item Dimensions	1.9 x 0.8 x 3 inches
Item Weight	1.6 ounces
Manufacturer	HM Digital, Inc.
Material Type	Plastic
Model	716186
Part Number	DM-1
Set Name	DM-1 In-Line Dual TDS Monitor
UPC	733169337600 891144000052 885169394012 885156810310
Unit Count	1.0 Count

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