Use this free chlorine injection pump calculator to find the correct feed rate for your well water chlorination system. Enter your well pump flow rate, target dosage, and solution strength — and get the exact speed and stroke dial settings for your metering pump.

How to Use This Chlorine Injection Pump Calculator

This chlorine injection pump calculator walks you through four simple steps to find your ideal pump settings. Here’s what you’ll need before you start:

Your well pump flow rate in gallons per minute (GPM). Check the label on your well pump or pressure tank, or ask your well driller. Most residential well pumps are between 5 and 20 GPM.
Your target chlorine dosage in parts per million (ppm). This depends on what contaminants you’re treating — see the dosage table below.
Your chlorine solution strength. Common options include household bleach (5.25%), ultra bleach (8.25%), or commercial sodium hypochlorite (10–12.5%).
Your pump’s rated capacity in gallons per day (GPD). This is printed on the pump label. The most common residential size is 38 GPD.

Chlorine Dosage Guide: How Many PPM Do You Need?

The right chlorine dosage depends on what’s in your well water. Use the table below to determine the ppm setting for your chlorine injection pump calculator inputs. These are general guidelines — always confirm with a water test.

Contaminant	Recommended Chlorine Dosage
Iron (clear water iron)	1 ppm chlorine per 1 ppm iron
Manganese	2 ppm chlorine per 1 ppm manganese
Hydrogen sulfide (rotten egg smell)	2 ppm chlorine per 1 ppm H₂S
Iron bacteria (slime, biofilm)	3–5 ppm chlorine
Coliform bacteria	1–2 ppm chlorine minimum
Combined iron + sulfur	Add dosages together (e.g., 3 ppm iron + 1 ppm H₂S = 5 ppm chlorine)

How to Find Your Well Pump Flow Rate

Check Your Pump or Pressure Tank Label

Most submersible well pumps have a label showing the rated GPM. Look on the side of the pump casing or on the pressure tank specifications. Common residential well pump flow rates range from 5 to 20 GPM.

Do a Bucket Test

Open an outdoor spigot (bypassing any filters or treatment) and time how long it takes to fill a 5-gallon bucket. Divide 5 by the number of minutes. For example, if it takes 30 seconds (0.5 minutes), your flow rate is 5 ÷ 0.5 = 10 GPM.

Ask Your Well Driller

Your well driller’s report includes the pump model and rated flow. This is usually the most accurate number to use in the chlorine injection pump calculator.

Most Popular: J-PRO-38 Chlorinator Package
Complete chlorine injection system with 38 GPD metering pump, solution tank, injection check valve, and tubing. Ready to install — just add bleach.

View J-PRO-38 Chlorinator Package

Choosing the Right Chlorine Injection Pump Size

After running the calculator, check where your required output (GPD) falls relative to the pump’s maximum capacity. Ideally, your pump should operate between 20% and 80% of its rated capacity for the best dosing accuracy.

Under 10% capacity: The pump is oversized. Consider a smaller pump or dilute your chlorine solution.
20–80% capacity: The sweet spot. Your pump has room to adjust up or down as needed.
Over 90% capacity: The pump is nearly maxed out. Consider the next size up.

Frequently Asked Questions About Chlorine Injection Pumps

What size chlorine injection pump do I need for my well?

It depends on your flow rate, target dosage, and solution strength. Use the chlorine injection pump calculator above to get an exact answer. Most homes with 7–15 GPM wells and standard chlorine dosages (1–5 ppm) do well with a 24 or 38 GPD metering pump.

What’s the difference between household bleach and pool chlorine?

Regular household bleach is typically 5.25–8.25% sodium hypochlorite. Pool chlorine or commercial bleach is stronger at 10–12.5%. Stronger solutions mean your pump injects a smaller volume to achieve the same dosage. Either works in a chlorine injection pump — just select the correct strength in the calculator.

How often should I refill the chlorine solution tank?

It depends on your daily water usage and injection rate. A typical household using 300 gallons per day with a 5 ppm dosage and 10% bleach solution will use roughly 0.5 gallons of solution per day. A 15-gallon solution tank would last about a month.

Do I need a contact tank with a chlorine injection system?

Yes, in most cases. Chlorine needs 5–20 minutes of contact time to oxidize iron, sulfur, and bacteria before the water reaches your filter. A 40–120 gallon retention tank is installed after the injection point and before the filter. For more on well water disinfection, see the Oregon State University well chlorination guide.

Can I use hydrogen peroxide instead of chlorine?

Yes, hydrogen peroxide is another option, especially for sulfur and iron. However, the dosing calculations are different. This calculator is specifically for sodium hypochlorite solutions. Peroxide pumps typically require a 7% solution and higher injection rates.

How do I test chlorine residual after installation?

Use a DPD test kit or digital chlorine meter to measure free chlorine at the farthest faucet from the injection point. You should see 0.2–0.5 ppm of free chlorine residual. If it’s too high, reduce the stroke setting. If it’s zero, increase the stroke.