The TERC Water Pump

for collecting water samples

Materials

syringe

syringe tubing (1 long length and 2 short lengths)

T-valve

2 check valves

film canister

fishing weight

glue

Constructing the TERC Water Pump

1 Glue the fishing weight to the bottom of the outside of the film canister.

2 In the lid of the film canister, cut a hole the size of a piece of tubing in the center, and then a smaller air hole off to the side.

3 Place one of the short lengths of tubing through the hole in the center of the canister lid. Seal this hole (but not the little hole) with glue so that it is watertight.

4 Attach one of the check valves to the short length of tubing on the inside of the lid (the valve will be inside of the canister), with the filter pointing away from the lid. Attach the canister with the weight on the bottom to the lid.

5 Attach the other end of the tubing to the bottom end of the T-valve, so that the T-valve is on the outside side of the canister lid.

6 Attach the second short length of tubing to one of the other ends of the T-valve.

7 Attach the second check valve to this piece of tubing, so that the filter is pointing toward the T-valve.

8 Attach the long length of tubing to the last end of the T-valve.

9 Attach the other end of the long piece of tubing to the syringe.

10 With a permanent marker, mark the long tubing in 50-cm lengths, starting from the intake check valve.

Using the TERC Water Pump

1 Lower the weighed canister into the water to the desired depth. The canister should remain vertical as it is lowered.

2 Slowly draw 50 cc of water into the tube. The water should not reach all the way to the syringe.

3 Slowly push the plunger back. The water sample will be forced into the canister for collection.

4 Quickly pull the canister to the surface, open it, and take your measurement. (This needs to be done especially quickly for a temperature reading, so you get the true temperature of the water.)

5 Rinse the tube four to five times between measurements.

Return to Water Dissolves Index

Return to Water Index