Flowmaster Gallon Meter Model: HLFM Click to enlarge

Product Description:
The Flowmaster measures how many
gallons of filtered water have gone through the system and alerts you
when it's time to change filters. You can program in the filter
capacity and when you reach the target number of gallons the Flowmaster
beeps. This is important for knowing when to change the pre-filter for
the Merlin-Garden Pro. It also ensures your system runs at its peak
efficiency at removing contaminants. Available in 3/8" quick connect
for the Merlin-Garden Pro & Tall Boy.