How often do you top off flooded batteries?

[Jim Hardesty]

what brand hydrometer did you buy?

Ken,
I don't recall, it's similar to this one. 

https://www.amazon.com/Mighty-Max-Battery-Hydrometer-product/dp/B00NCWAPEY/ref=sr_1_9?dchild=1&keywords=Battery+Hydrometer&qid=1604405346&sr=8-9

Any good auto parts store should have them.  I saw hits on google for utube how-to's.  For me important thing is readings between cells and comparing to old readings.   I take readings in the spring, may be a couple of times over a couple of weeks, then only if I'm suspicious of the batteries.
I may visit Shamrock next couple of days, will try to remember to take pictures of my plumbing pvc case.
Jim

[scgunner]

Thanks Noah, you learn something new everyday.

[Ken Krawford]

Thanks for the info and the link Jim.  My lack of trust with the instrument stemmed from test the same cell 3 times and getting a different reading each time.  It doesn't seem like there's a lot of specialized technique involved.  Place tube in cell, squeeze bulb to pull electrolyte in - keep hydrometer vertical and read.

[Roc]

Hi Jim.
Great idea of making a case out of PVC pipe!!  I never knew how I should store the hydrometer with battery acid on it. Thanks for the tip!!

[Jim Hardesty]

A couple of pictures.  Also notice the well rinsed Arizona tea jug for the distilled water.  More rugged than the jugs distilled water comes in, and a refreshing beverage.
Jim

[Paulus]

I also check my batteries weekly for levels.  Every season I disconnect all cables and check the voltage in each battery and record this in my log book. 
Paul
PS:  My wife and I spend 7 weeks sailing on Lake Michigan and also around Drummond Island and the St. Mary's river.  Missed the North Channel.