Some Birthday Science

Posted on 09 Sep 2021 by Steve Markham

I got a birthday present in the mail today, a new Sawyer filter!

The new, big filter is less than twice the weight, flows easier and faster, and has threads on the clean side!
The new, big filter is less than twice the weight, flows easier and faster, and has threads on the clean side!

The new filter also came with a coupler, a tube, and a few threaded nozzles. My gravity system is getting a major upgrade on the next trip!

Adele is home from school today, so we decided to measure the flow rates to see how much better the new filter is. First we tried timing how long it took to gravity filter a 16oz bag of tap water through each filter. It took about 5 minutes 16 seconds for the big filter to stop flowing. But there was still a bit of water left in the bag, and I wasn’t sure it would be fair if the old filter stopped with a different amount leftover. Luckily that wasn’t an issue–I ran out of patience around the 10 minute mark with the old filter.

Next we tried filtering into a bowl on the kitchen scale with a stopwatch going. That way we could measure grams filtered at 30 second intervals. It turns out the scale turns itself off after 4 or 5 minutes if the weight is increasing steadily. Four trials, each combination of new/old filter and 16/64 oz water bags:

The new filter is so fast that you can see the pressure drop as it runs out of water (red line)
The new filter is so fast that you can see the pressure drop as it runs out of water (red line)

It can filter 1L in 2.6 minutes without even squeezing. I also think it’s interesting how much the bigger bag helps the old filter (40% faster) compared to the new one (125% faster). Maybe I’ll get out my gallon bag next.

Thanks Andy and Nancy!