Motivated by a recent discussion (and a not so recent one) about foot pumps, Joanie and I used the Guzzler 400 from her boat to measure flow rates with and without a strum box. The strum box was made from 1.5 in PVC as described in the recent Sea Kayaker article - 1.5 in diam, 8 slots 0.3 in deep by 0.2 in wide. We pumped from a full bucket into an empty one for 1 min, or until we heard air being drawn into the intake. We then measured the volume of pumped water with a 1 gal jug and a 1 l beaker. Two measurements were made with the strum box against the bottom of the bucket, and two measurements were made with the strum box held at least one hose diameter up from the bottom. We tried to depress the actuator just before it completely filled the pump body, so that the intake rate was controlling the pump rate, but there was little or no dead time.

Strum box against bottom: 3.05 gal/min and 3.45 gal/min

Strum box off the bottom: 4.03 gal/min and 3.89 gal/min

So, the strum box slowed the pump rate by about 20%. But perhaps the more interesting comparison is 3 to 4 gal/min compared to the advertised 10 gal/min.

Sam