A dosing pump can be the right brand, flow capacity and seal material yet still deliver the wrong result if its ratio does not match the job. When asking, what dosing ratio do I need, start with the required concentration at the point of use - not the ratio printed on the existing injector or the size of the chemical drum.
For a livestock medication line, that may mean delivering a prescribed amount of product per litre of drinking water. In fertigation, it may mean achieving a target nutrient concentration after the irrigation water and stock solution have mixed. For cleaning and sanitation, the target is usually the chemical supplier’s stated use dilution. The pump or water-powered injector must be capable of reliably delivering that concentration across your actual operating flow range.
What dosing ratio do I need for the application?
A dosing ratio describes how much concentrate is introduced into the carrier water. A 1:100 ratio means one part chemical concentrate to 100 parts water, which is broadly equivalent to 1% dosing. A 1:200 ratio is 0.5%, while 1:50 is 2%.
The lower the second number, the stronger the dose. This catches people out when comparing injectors. A unit adjustable from 0.2% to 2% can dose from roughly 1:500 to 1:50. It cannot deliver a 1:1,000 ratio accurately, even if the required chemical volume appears small over a day.
The required ratio should come from the product label, treatment protocol, agronomist, veterinarian, water treatment plan or chemical technical data sheet. Do not select a ratio by estimating how long a drum should last. Chemical usage can be useful as a cross-check, but it is not a substitute for a specified final concentration.
Convert the instruction into a percentage or ratio
Many products are specified in millilitres per litre rather than as a percentage. The conversion is straightforward:
Dosing percentage = millilitres of concentrate per litre of final water mix ÷ 10
For example, if the instruction is 2 mL per litre of water, the required dose is 0.2%. That is approximately a 1:500 ratio. If the instruction is 10 mL per litre, the required dose is 1%, or approximately 1:100.
Where instructions are given per 1,000 litres, divide the concentrate volume in litres by 10 to find the percentage. For instance, 5 L of concentrate per 1,000 L of water equals 0.5%, so a 1:200 injector setting is required.
These calculations assume the concentrate is being injected directly. If you are drawing from a pre-diluted stock solution, calculate from the strength of that stock solution rather than the original product. This is common in hydroponics and fertigation, where a concentrated nutrient stock may be prepared first to improve mixing or manage multiple inputs.
Match the ratio to the pump’s adjustment range
The best dosing equipment is not simply the model that includes your target ratio. For dependable control, choose a unit where the target sits comfortably within its adjustable range.
If your required dose is 1%, an injector rated from 0.2% to 2% is generally well suited. A model rated from 1% to 10% may technically reach 1%, but it is operating at the bottom of its adjustment range. Fine adjustment, water-pressure changes and wear over time can have a greater effect at the edge of a unit’s range.
The same principle applies to very low-dose applications. If you need 0.05%, look for a low-ratio injector or dosing pump designed for that level of precision. Trying to achieve it with a 0.2% minimum-ratio injector by diluting the product in a large drum may work in some cases, but it adds handling, mixing and compatibility risks. It can also create storage concerns where a diluted chemical is less stable than the original concentrate.
For applications that regularly change between low and high doses, an adjustable injector may offer useful flexibility. Where the application always runs at one ratio and demands tight repeatability, a fixed-ratio injector can be the more practical choice.
Ratio is only one part of correct sizing
A correct ratio will not compensate for an undersized or oversized unit. Water-powered injectors and chemical dosing pumps must also suit the flow, pressure and operating pattern of the system.
A livestock shed may have low overnight water demand followed by a sharp peak when animals drink after feeding. A greenhouse irrigation zone may run only in short, high-flow cycles. A water treatment plant may have steady 24-hour flow but varying pressure. In each case, check that the equipment can maintain the nominated dose at both the minimum and maximum flow likely to occur.
Pay particular attention to minimum flow. Some injectors need a certain flow rate before they begin drawing concentrate accurately. If the flow falls below that threshold, the injector may stop dosing or dose inconsistently. This matters on small irrigation zones, low-demand trough lines and systems with variable-speed pumps.
Pressure loss also deserves attention. A water-powered injector creates a pressure drop as water passes through it. If the downstream system has marginal pressure - such as long irrigation runs, filters, solenoids or elevated tanks - assess whether the remaining pressure will still meet the application requirement.
Calculate concentrate consumption as a check
Once you know the ratio and water flow, calculate the concentrate draw rate:
Concentrate required per hour = water flow per hour × dosing percentage
At 10,000 L/hour and 0.5% dosing, the injector will draw 50 L/hour of concentrate. At 1,000 L/hour and 0.2%, it will draw 2 L/hour.
This check helps select the right drum size, suction tubing, foot valve and storage arrangement. It also identifies situations where the chemical container will empty sooner than expected. Running a dosing system dry can interrupt treatment and, depending on the chemical and equipment, may affect seals, suction components or calibration.
Consider chemical strength and stock solution design
Two operators can target the same final concentration but need different injector ratios because they use different product strengths. For example, a highly concentrated fertiliser may only need 0.2% injection, while a lower-strength liquid formulation may require 1% or more to achieve the same nutrient result.
This is why product concentration matters before equipment selection. Confirm whether the required instruction refers to product volume, active ingredient concentration, available nutrient content or another measurement. A dose rate for chlorine, acid, trace elements or veterinary medication is not interchangeable between products just because the containers look similar.
For multi-part nutrient programs, separate stock tanks and compatible injection points may be necessary. Mixing incompatible concentrates together can cause precipitation, blocked filters and uneven crop feeding. In these systems, the ideal ratio is only useful if the stock solution remains stable and can be drawn consistently.
Do not overlook seals, materials and calibration
The chemical being dosed may determine the equipment configuration as much as the ratio does. Acidic products, alkaline cleaners, oxidisers, oils and some animal-health chemicals can affect seals, housings and valves differently. A pump that has the right ratio but unsuitable wetted materials can fail early or contaminate the process.
Check compatibility with the chemical supplier’s data and select the appropriate seal option, such as PVDF, Viton, EPDM or other materials specified for the product. Also consider water quality. Sediment, iron, scale and debris can affect check valves, meters and injectors, so filtration and routine maintenance may be required.
Calibration is the final safeguard. Measure the actual amount drawn from the concentrate container over a known volume of water or a timed run at normal operating flow. Compare the result with the expected draw rate, then adjust if the equipment allows it. Repeat the test after installation changes, chemical changes, seal replacement or a noticeable shift in water pressure.
AgriDosing can help narrow the selection by checking ratio range, operating flow, pressure, chemical compatibility and the practical details of your installation. Bring the required final dose, product name, expected water flow and available pressure to the conversation. Those four details usually turn a broad equipment search into a reliable dosing solution that performs when the system is under real operating demand.