All Water Treatment Calculators
Every calculator on Practical Notes Lab, in one place. Type to filter instantly.
Hydraulics & Units (20)
Equalization Basin Volume Calculator
Size an equalization basin from your diurnal flow pattern — peak factor and hours above average flow. Free wastewater design tool.
Darcy-Weisbach Head Loss Calculator
Compute pipe friction head loss with the Darcy-Weisbach equation and the Haaland friction factor — velocity, Reynolds number, and pipe roughness included. Free hydraulics tool for water engineers and operators.
Minor Loss (Fittings & Valves) Calculator
Add up K-values for elbows, tees, and valves to get minor head loss in feet of head. Free pipe hydraulics tool for water engineers and operators.
NPSH Available Calculator
Check pump suction adequacy: NPSH available from site elevation, water temperature, static suction head, and suction-line losses. Free pump hydraulics tool for water engineers and operators.
Open Channel Normal Depth Calculator
Solve Manning's equation for normal depth, velocity, and Froude number in rectangular and trapezoidal channels. Free open-channel hydraulics tool.
Orifice Flow Calculator
Flow through an orifice, nozzle, or port from head and diameter — Q = Cd·A·√(2gH). Free hydraulics tool for water engineers and operators.
Parallel Pump Operation Calculator
Compare one pump vs two identical pumps in parallel against your system curve — see the real flow gain and the diminishing returns. Free pump station tool.
Parshall Flume Flow Calculator
Rate Parshall flume flow from upstream head with standard free-flow coefficients for 1-inch through 8-foot throats. Free open-channel flow tool.
Pump Affinity Laws Calculator
Predict pump flow, head, and power at a new speed or with a trimmed impeller using the affinity laws. Free pump hydraulics tool for water engineers and operators.
Pump Specific Speed Calculator
Find a centrifugal pump's specific speed (Ns) from speed, flow, and head — and see whether the duty calls for a radial, mixed, or axial impeller. Free pump selection tool.
Pump System Curve Calculator
Build a pump system curve H = Hstatic + KQ² from static head and one duty point — tabulated head at any flow. Free pump selection tool for water engineers and operators.
Pump Wire-to-Water Efficiency Calculator
Turn pump flow, head, and metered kW into overall wire-to-water efficiency — see how much power is wasted. Free pump energy tool.
Water Hammer Surge Pressure Calculator
Estimate surge pressure from sudden valve closure or pump trip with the Joukowsky equation — wave speed by pipe material included. Free hydraulics tool for water engineers and operators.
Weir Flow Calculator
Compute flow over rectangular and 90-degree V-notch weirs from a head reading. Field-ready open-channel flow estimates for weir boxes and channels. Free hydraulics tool.
Detention Time Calculator – HRT for Tanks & Basins
Calculate hydraulic retention time (HRT / detention time) for rectangular or circular tanks from dimensions and flow. SI and US units. Free online tool.
Hazen-Williams Calculator – Pipe Flow, Velocity & Head Loss
Free Hazen-Williams calculator: compute flow velocity and friction head loss in pressurized water pipes. Supports SI and US units.
Manning Equation Calculator – Open Channel Flow
Free Manning equation calculator for open channel flow. Compute discharge and velocity for rectangular channels and full circular pipes (SI units).
Water Unit Converter – Concentration, Flow, Pressure, Hardness & More
Free water treatment unit converter: mg/L to ppm, hardness (gpg, °dH, meq/L), flow (MGD, gpm, L/s), pressure (psi, m head), volume, mass loading and temperature.
Pump Horsepower Calculator – WHP, BHP, TDH & Motor Size
Calculate pump water horsepower, brake horsepower, motor HP and total dynamic head from flow. Includes energy use, cost and motor sizing. Free online calculator.
Wet-Well Cycle Time Calculator – Lift Station Pumps
Calculate lift-station wet-well cycle time, pump starts per hour and run percent for min/avg/peak inflows. Free operator calculator.
Treatment & Disinfection (26)
Fluoride Dose & Feed Rate Calculator
Calculate fluoride feed rates for water fluoridation — sodium fluoride, sodium fluorosilicate, or fluorosilicic acid — from flow and target dose. Free operator tool.
Iron & Manganese Oxidant Dose Calculator
Estimate theoretical chlorine or permanganate dose for iron and manganese oxidation from raw water Fe and Mn levels. Stoichiometric minimum for groundwater plants. Free calculator.
Lime–Soda Ash Softening Dose Calculator
Calculate lime and soda ash doses for lime-soda softening from CO2, calcium and magnesium hardness — with as CaCO3 conversions. For operators and certification exam prep.
Water Main Disinfection Calculator (AWWA C651)
Size chlorine doses for new water main disinfection per AWWA C651 — tablet, continuous feed, and slug methods, plus flushing flow at 2.5 ft/s. Free calculator for contractors and operators.
Alum Coagulant Dose Calculator
Turn jar-test alum doses into dry pounds per day or liquid alum gallons per day. Free water treatment operator tool.
Breakpoint Chlorination Dose Calculator
Estimate theoretical breakpoint chlorination dose from ammonia-N and chlorine demand. Free water disinfection operator tool.
Chloramine Cl₂:NH₃-N Ratio Calculator
Check your chlorine-to-ammonia weight ratio for monochloramine formation versus breakpoint risk. Free water disinfection operator tool.
Chlorine Decay Calculator
Project chlorine residual decay with first-order kinetics C=C0·e^(−kt), plus half-life and time to a target residual. Free water treatment operator tool.
Chlorine Dioxide Dose Calculator
Convert chlorine dioxide dose (mg/L) to pounds per day, with MRDL and chlorite MCL reminders. Free water treatment operator tool.
Flocculation Gt (Camp Number) Calculator
Compute the Camp number (Gt) for flocculation basins from velocity gradient G and detention time. Free water treatment operator tool.
Ion Exchange Softener Calculator
Size water softener regenerations: capacity in grains, salt dose per cubic foot, and days between regenerations. Free water treatment operator tool.
Ozone Transferred Dose Calculator
Size ozone disinfection: compute transferred ozone dose (mg/L) from gas flow, inlet and off-gas concentrations. Free water treatment operator tool.
PAC Dose Calculator — Powdered Activated Carbon
Convert powdered activated carbon dose (mg/L) to lb/day feed rate for taste-and-odor control. Free water treatment operator tool.
Polymer Flocculant Dose Calculator
Convert polymer jar-test doses (mg/L active) to product pounds per day and liquid gallons per day. Free water treatment operator tool.
Rapid Mix G-Value Calculator
Size rapid-mix velocity gradient G for coagulation basins from mixer power and tank volume. Free water treatment operator tool.
RO Recovery and Concentrate Calculator
Check reverse osmosis recovery, concentrate flow, and concentrate TDS from feed and permeate flows. Free water treatment operator tool.
UV Dose Calculator
Compute UV dose from average intensity and exposure time, and compare against NSF/ANSI 55 and UVDGM targets. Free water treatment operator tool.
Dechlorination Dose Calculator
Size sodium bisulfite or sulfur dioxide feed to neutralize chlorine residual before discharge. Free wastewater operator tool.
Wastewater Chlorine Contact Calculator
Chlorine feed rates and modal contact times at average and peak flow for wastewater disinfection. Free operator tool.
BOD / COD Removal Efficiency Calculator
Calculate wastewater treatment removal efficiency (%) from influent and effluent BOD or COD concentrations. Free online calculator.
Chemical Dosing Calculator – Water Treatment Feed Rate
Calculate chemical feed rate for water treatment from dose (mg/L) and flow. Results in lb/day and kg/day. Free online dosing calculator.
Chlorine Dose Calculator – Demand + Residual & Decay
Calculate required chlorine dose from demand plus target residual, chemical feed rates, and first-order chlorine decay with half-life. Free water treatment calculator.
CT Calculator – Chlorine Disinfection Contact Time
Calculate CT (concentration × time) for chlorine disinfection from residual and contact time, with baffling factor. Free online tool.
Chemical Feed Pump Calibration Calculator – Drawdown Test
Calibrate a chemical feed pump with a drawdown test: measured mL/min, gph, gpd, actual dose vs target dose with pass/fail. Free operator calculator.
Langelier Saturation Index (LSI) Calculator – Water Stability
Calculate the Langelier Saturation Index and Ryznar Stability Index from pH, temperature, calcium, alkalinity and TDS. Free water stability calculator.
Log Removal Calculator – Percent & Log Removal
Calculate percent removal and log removal (log credit) for single or multi-barrier water treatment, with SWTR and LT2 context. Free calculator.
Activated Sludge Process Control (14)
Nitrification Alkalinity Requirement Calculator
Check whether nitrification will exhaust your alkalinity — 7.14 mg/mg rule, denitrification credit, and supplemental chemical feed rates. Free wastewater operator tool.
BOD Volumetric Loading Calculator
Check aeration basin organic loading in lb BOD per 1000 ft³ per day against typical design ranges. Free wastewater operator tool.
Lagoon Detention Time Calculator
Check facultative lagoon performance: detention time in days and surface BOD loading in lb/acre-day from flow, dimensions, and BOD load. Free wastewater operator tool.
MBBR Media Fill Calculator
Size moving bed biofilm reactor carriers: fill percent, media volume, and total protected biofilm surface area. Free wastewater operator tool.
MLSS Inventory Calculator
Total pounds of MLSS across your aeration basins — the starting point for SRT control and wasting decisions. Free wastewater operator tool.
Observed Biomass Yield Calculator
Estimate net waste sludge production from yield, decay, and SRT — observed yield and lb/day of biomass to waste. Free wastewater operator tool.
RAS Flow Rate Calculator
Set return activated sludge pumping from a clarifier mass balance: RAS percent, RAS flow in MGD and gpm. Free wastewater operator tool.
SBR Cycle Time Calculator
Lay out a sequencing batch reactor cycle: phase times, cycles per day, volume per cycle, and decant rate. Free wastewater operator tool.
Trickling Filter NRC Efficiency Calculator
Predict trickling filter BOD removal with the NRC formula: recirculation factor, organic loading, and expected efficiency. Free wastewater operator tool.
F/M Ratio Calculator – Food to Microorganism Ratio
Calculate the food-to-microorganism (F/M) ratio for activated sludge from flow, influent BOD, aeration volume and MLVSS. Free online tool.
Oxygen Requirement Calculator – Aeration Demand
Estimate oxygen requirement and blower air flow for activated sludge from BOD removal and nitrification. Free online aeration calculator.
SRT Calculator – Sludge Age (MCRT) for Activated Sludge
Calculate solids retention time (SRT), also called sludge age or MCRT, for activated sludge from MLSS, aeration volume, WAS flow and effluent TSS. SI and US units.
SVI Calculator – Sludge Volume Index
Calculate the sludge volume index (SVI) from 30-minute settled sludge volume and MLSS. Includes settleability interpretation guide. Free online tool.
WAS Wasting Rate Calculator – Waste Activated Sludge
Calculate waste activated sludge (WAS) wasting rate from MCRT target or MLSS inventory reduction. Results in lb/day, MGD, gpd and pump gpm. Free operator calculator.
Clarification & Filtration (7)
Filter Loading Rate Calculator
Check filter loading rate in gpm/ft² from flow and filter area. Free water filtration operator tool.
Unit Filter Run Volume (UFRV) Calculator
Compute unit filter run volume (UFRV) in gal/ft² from filter flow, area, and run time. Free filtration performance tracking tool.
Grit Channel Velocity Calculator
Check horizontal velocity and detention time in grit channels — hold ~1 ft/s for effective grit removal. Free operator tool.
Primary Clarifier Removal Calculator
Estimate primary clarifier TSS and BOD removal from surface overflow rate. Free wastewater treatment tool.
Clarifier Loading Rate Calculator – SOR & SLR
Calculate secondary clarifier surface overflow rate (SOR) and solids loading rate (SLR) from flow, MLSS and clarifier dimensions. Free operator calculator.
Filtration & Backwash Rate Calculator – gpm/ft²
Calculate filter filtration rate, backwash rate, rise rate and backwash water volume from flow and filter area. Free operator calculator.
Weir Loading Rate Calculator – gpm/ft & gpd/ft
Calculate clarifier weir loading rate (weir overflow rate) in gpm/ft and gpd/ft from flow and weir length or diameter. Free operator calculator.
Compliance & Monitoring (1)
Lead and Copper 90th Percentile Calculator
Calculate the LCR 90th percentile for lead and copper tap sampling results — paste results, get the ranked value, action-level comparison, and EPA method notes. Free tool for water systems and compliance staff.
Water Chemistry (4)
Calcium Carbonate Precipitation Potential (CCPP) Calculator
Estimate how much calcium carbonate your water will precipitate or dissolve (CCPP) from pH, calcium, alkalinity, temperature and TDS. Free water treatment operator tool.
Larson-Skold Corrosivity Index Calculator
Screen chloride and sulfate corrosivity toward steel with the Larson-Skold index from chloride, sulfate and alkalinity. Free water treatment operator tool.
Puckorius Scaling Index Calculator
Predict scaling versus corrosion with the Puckorius Scaling Index, which accounts for the buffering capacity of the water. Free water treatment operator tool.
Ryznar Stability Index Calculator
Predict calcium carbonate scaling versus corrosion with the Ryznar Stability Index from pH, temperature, TDS, calcium and alkalinity. Free water treatment operator tool.
Distribution System (5)
Water Tank Turnover Time Calculator
Check storage tank turnover time and water-age risk for your distribution system from tank volume and average daily demand. Free water operator tool.
Fire Flow Requirement Calculator (ISO Method)
Estimate needed fire flow (NFF) for a nonsprinklered building with the ISO method — construction factor, occupancy factor, exposure surcharge, and duration. Free water distribution planning tool.
Hydropneumatic Tank Drawdown Calculator
Size the usable drawdown of a hydropneumatic pressure tank from precharge and cut-in/cut-out pressures with Boyle's law. Free water distribution tool.
Pressure Zone HGL Calculator
Convert between hydraulic grade line elevation and static pressure in psi — check available pressure at any service elevation. Free distribution system tool.
Thrust Block Calculator
Thrust force at pipe bends and dead ends and the required thrust-block bearing area, from test pressure and diameter. Free water distribution tool.
Laboratory & General (9)
Dissolved Oxygen Saturation Calculator
Look up dissolved oxygen saturation (mg/L) for any water temperature, corrected for elevation. Free water lab and operator tool.
Alkalinity Titration Calculator
Convert lab titration volumes to alkalinity as CaCO3 — total, phenolphthalein, and hydroxide/carbonate/bicarbonate split per APHA 2320. Free lab tool.
Composite Sampler Pacing Calculator
Set up flow-paced composite sampling — aliquot volume, gallons per aliquot, and flow-meter pulses per aliquot from your bottle size and daily flow. Free sampling tool.
Dilution Calculator (C1V1 = C2V2)
Make any lab dilution right the first time: stock volume to pipette and diluent to add for a target concentration. Free lab math tool for water operators.
Water Hardness as CaCO3 Calculator
Convert calcium and magnesium to total hardness as CaCO3 with the USGS hardness scale. Free water chemistry tool.
Molarity and Normality Calculator
Convert grams, molecular weight, and volume to molarity and normality for titrants and standards. Free lab calculation tool.
Percent Solution Preparation Calculator
Prepare exact % w/v lab solutions: grams of chemical to weigh for any target volume, corrected for reagent purity. Free lab prep tool.
Reynolds Number Calculator (Pipe Flow)
Check whether pipe flow is laminar or turbulent: Reynolds number from velocity, diameter, and water temperature. Free hydraulics tool.
Temperature Correction (Theta) Calculator
Adjust biological rate constants for temperature: kT = k20 · θ^(T-20) with standard theta values. Free wastewater process tool.
Nutrient Removal (5)
Anoxic Volume Fraction Calculator
Size the anoxic zone for biological nitrogen removal — anoxic volume fraction, anoxic HRT, and internal recycle guidance. Free wastewater design tool.
Denitrification Methanol Dose Calculator
Size methanol feed for denitrification: 2.47 mg/mg theoretical dose, dissolved-oxygen correction, and lb/day plus gal/day feed rates. Free wastewater operator tool.
Denitrification Oxygen Credit Calculator
Denitrification pays back oxygen — 2.86 mg O2 per mg NO3-N. Turn your nitrate removal into lb/day of aeration savings. Free wastewater tool.
Nutrient Addition (N and P) Calculator
Check whether your wastewater has enough nitrogen and phosphorus for biological treatment — 100:5:1 BOD:N:P rule, deficits, and urea plus phosphoric acid feed rates. Free wastewater operator tool.
Phosphorus Precipitation Dose Calculator
Alum and ferric doses for chemical phosphorus removal — molar-ratio based mg/L, lb/day, and gal/day feed rates. Free wastewater operator tool.
Solids Handling & Digestion (9)
Chemical Sludge Production Calculator
Estimate extra sludge from phosphorus precipitation or lime — AlPO4, FePO4, hydroxides, and CaCO3 stoichiometry. Free solids tool.
Primary Sludge Volume Calculator
Convert primary sludge solids removed into dry pounds and pumpable gallons per day. Free solids handling tool.
Anaerobic Digester Loading Calculator
Check anaerobic digester volatile-solids loading and solids retention time against conventional and high-rate design ranges. Free wastewater operator tool.
Belt Press Solids Capture Calculator
Measure belt press or dewatering performance: solids capture percent and filtrate TSS from feed and cake data. Free wastewater operator tool.
Dewatered Cake Solids Calculator
Close the mass balance around dewatering: wet cake tons per day and filtrate TSS from feed solids, cake solids, and capture. Free wastewater operator tool.
Dewatering Polymer Dose Calculator
Convert dewatering polymer dose in lb per dry ton to daily feed rates — active polymer, product, and gallons per day. Free wastewater operator tool.
Digester Gas Production Calculator
Estimate anaerobic digester biogas yield from volatile solids destroyed — gas volume, methane, and heating value. Free wastewater operator tool.
Digester Heating Requirement Calculator
Size anaerobic digester heating: sludge warm-up load plus wall heat losses in BTU/day. Free wastewater operator tool.
Gravity Thickener Solids Loading Calculator
Check gravity thickener solids loading rate in lb/day per ft² against design ranges for primary sludge and WAS. Free wastewater operator tool.
Collection System (3)
Force Main Velocity Calculator
Check force main velocity from flow and pipe diameter against 2 to 5 ft/s guidance. Free wastewater collection system tool.
Minimum Self-Cleansing Slope Calculator
Minimum sewer slope for self-cleansing velocity at full flow, from Manning's equation rearranged. Free collection system design aid.
Sewer Full-Flow Capacity Calculator
Full-flow capacity and velocity of circular sewers by Manning's equation. Free wastewater collection system tool.
Stormwater (5)
Curb Inlet Capacity Calculator (HEC-22)
Size curb-opening inlets on grade with the HEC-22 weir equation — enter opening length and flow depth to get intercepted flow. Free stormwater design tool.
Detention Basin Volume Calculator
Planning-level detention storage estimate from the runoff volume difference — enter pre/post runoff coefficients, area, storm depth, and release rate. Free stormwater tool.
Gutter Flow Calculator (HEC-22)
Compute street gutter capacity with the HEC-22 modified Manning equation — enter cross slope, longitudinal slope, spread, and n. Free stormwater design tool.
Rational Method Runoff Calculator
Estimate peak stormwater runoff with the Rational Method (Q=CIA) — pick a runoff coefficient, enter rainfall intensity and drainage area. Free stormwater design tool.
Time of Concentration Calculator (Kirpich)
Compute stormwater time of concentration with the Kirpich equation — enter flow path length and slope to get Tc for your IDF lookup. Free drainage design tool.
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