306-25 Metering Pump

306-25 Metering Pump
306-25 Metering Pump

The 306-25 Metering Pump reduces mixing time and waste on large projects. Great for metering larger quantities of 105 Resin and 205 Fast or 206 Slow (5:1 ratio) Hardeners. A carrying handle allows you to move the pump where the work is. Reservoirs hold one gallon of resin, one quart of hardener. Dispenses approximately 0.5 fl oz of resin/hardener per pump stroke (about 1 qt per minute).

306-25 Metering Pump Instructions (pdf)

Our 306 Model A Dispensing Pumps consist of two separate, parallel systems, one for the resin and one for the hardener. Each has a spring-loaded poppet type intake valve, a piston with an O-ring seal, and a spring-loaded ball check exhaust valve. The pump will deliver approximately ½ oz. of resin/hardener per pump stroke. The reservoirs hold one gallon of resin and one quart of hardener.


CAUTION—Remove all materials from Resin and Hardener reservoirs and be sure the reservoirs are clean before filling.

Prime the hardener system first. Fill the hardener reservoir with hardener. Pump the operating handle until hardener flows evenly from the spout without emitting air. Ten to twenty strokes of the handle should produce hardener at the spout. If not, use a stick or dowel to hold down the intake valve screw head inside the reservoir while slowly pumping the handle. This will allow trapped air to escape the valve and hardener to reach the piston.

After the hardener side is working properly, fill the resin reservoir and prime the resin system. Dispense the resin and hardener into separate, clean containers, or the original resin and hardener cans. After both systems are working, return the dispensed resin and hardener to the proper reservoirs.

Note: When filling the reservoirs do not get any resin in the hardener reservoir, or hardener in the resin reservoir. Always keep one reservoir covered while filling the other. Keep reservoirs covered at all other times to prevent contamination. Once primed, the pump should not be allowed to dry out. Dried hardener can damage the piston seal and clog the passages and valves. For this reason, the ratio is not checked at the factory.

Ratio Verification with 206-25 Metering Pump

WARNING! Check the ratio of resin to hardener dispensed by the pump before using the epoxy on your project. Recheck the ratio periodically or if you later experience incomplete or unusually fast or slow curing. Always recheck the ratio after refurbishing a 306 pump with the Epoxy Pump Rebuild Kit.

By weight

The most accurate method of checking the ratio is by weight. Dispense at least five strokes of resin and hardener into separate, pre-weighed containers. Weigh each of the samples on a balance or gram scale to determine the net weight of each. Divide the net weight of the resin by the net weight of the hardener to find the ratio of resin to hardener. The ideal or target ratio and the acceptable ratio ranges for each resin/hardener combination are shown in the charts below. Deviations beyond the acceptable range in either direction will result in an incomplete cure and significant weakening of the epoxy.

By volume

The ratio can also be checked by volume. Pump at least five strokes of resin and hardener separately into the two graduated measuring cups included with the pump. Set the cups on a level surface to accurately determine the volume of resin and hardener, in either ounces or milliliters. Divide the volume of resin by the volume of hardener. The ideal or target ratio and the acceptable ratio range is shown in the chart below. The ratio by volume is different than the ratio by weight because hardener has a lower density (greater volume per unit of weight) than resin.

This check can be done with any two identical, narrow, cylindrical containers. Measure the levels of the dispensed resin and hardener in the containers with a ruler. Divide the measured height of the resin by the measured height of the hardener to find the ratio. Monitor the resin/hardener ratio by examining cured epoxy left in mixing cups. If the residue is not sufficiently hard after the appropriate cure time has passed, recheck the pump ratio.

Acceptable ratio ranges for WEST SYSTEM 5:1 ratio Resin and Hardeners (205 & 206) with the 306-25 Epoxy Metering Pump
Resin/Hardener Weight Ratio Volume Ratio
Maximum Minimum Maximum Minimum
105/205 4.8:1 6.0:1 4.4:1 5.5:1
105/206 4.8:1 6.2:1 4.3:1 5.5:1


Learn more about mixing epoxy in large batches by reading Big Batch Mixing Methods by Tom Pawlak in Epoxyworks 9.