Safe method for measuring accurate water volume?

[WuTang]

I just bought a white food safe 32 Gallon Rubbermaid Brute container to hold my saltwater for water changes. Do you guys have a technique to measure accurate water volume in your container? Possibly using a mathimatical formula to make level marks? I'd like to be able to fill my "round" container exactly at 20 Gallons and 30 Gallons. I don't think I have a container that's exactly 1 Gallon to go by. Also, is there a "safe" marker I should be using to make level marks? I have a bunch of "Sharpie" markers but I'm not sure if the ink will leak anything bad into the water. I appreciate any of your thoughts and ideas.

[Samper]

I use two five gallon buckets for water changes. I fill one to about 4.5 gallons then add salt throughout the first day until it's at about 1.025 SG letting it mix with a powerhead for a week. When it's change time I just siphon the water out until the buckets levels are even. Empty the old water and siphon the new water back in.

[scubadude]

Do you guys have a technique to measure accurate water volume in your container? Possibly using a mathimatical formula to make level marks?

Simple way to figure the gallon capacity of a tank is to take Length x width x height (using ft.)
For Example a tank with measurements 4'x2'x2' = 16
then you take 16 and multiply it by 7.5 which is how many gallons is in a cubic foot
16 x 7.5 = 120 (this is your volume in gallons)

[scubadude]

Heres some very helpful calculators that will do it for you

http://www.aquadyntech.com/sitetools.html

They got a good head calculator too ;)

[WuTang]

http://www.aquadyntech.com/sitetools.html

Just tried the volume calculator for round tanks/containers and it's currently not giving volume in gallons. It's possibly broken? I'm curious on what their formula looks like and if I can enter inches instead. It only gives you the option to enter measurements in feet or gallons.

[ereefic]

I take a 5 gal. container, that is marked every half gallon. Fill it up to 5 gal. and dump it in an empty trash can. Do this 5 times and mark where the waterline is at. Add one more and mark where the 30 gal. line is.

[WuTang]

Thanks for all your responses. I found a 6 quart container with accurate measuring marks at a restaurant supply store for 3 bucks (should come in handy for other things too). I'll just use it to get accurate measurement marks for 10, 20, and 30 Gallons in my Brute container.

Although, can someone recommend a "Food Safe" measuring stick that I can use to check the water levels in the future? Or, would a sharpie marker be okay to write on the inner walls? I know the ink will fade over time and I'm not sure if it will leak anything bad in the water.

[ereefic]

Got a length of PVC pipe laying around? Slap some duct tape on your different measurements and TaaDaaaaaa, a measuring stick.

[Ninong]

http://www.aquadyntech.com/sitetools.html

Just tried the volume calculator for round tanks/containers and it's currently not giving volume in gallons. It's possibly broken? I'm curious on what their formula looks like and if I can enter inches instead. It only gives you the option to enter measurements in feet or gallons.

I just tried it and it is giving the volume in gallons provided that you calculate it in cubic feet first. You don't need to enter inches, just convert the inches to feet.

For example: I used an estimated 0.79' for the tank radius, an estimated 2.19' for the tank water depth and it gave me 4.294 cu. ft. and 32.076 gallons. That calculator would be accurate for a flat bottomed, straight sided cylinder. Obviously your Rubbermaid Brute container is not perfectly flat and it is not straight sided, it is larger at the top than it is at the bottom. You can adjust for that by averaging the variation in diameter from top to bottom if you are so inclined. Since I'm one of those nitpicky types, I will point out that Pi is not 3.1417 as they are using, it's 3.14159 or 3.1416 if you round it up. Or you could carry it out to a couple hundred places if you're truly anal or an M.I.T. grad. (Actually M.I.T. grads use 3.14159)

P.S. -- Exact measurements of a 32-gal Rubbermaid Brute container: http://www.usplastic.com/pdfdatafile...ing06-2002.pdf

P.P.S. -- Here is Pi carried out to eight decimal places: 3.14159265 It can be carried out to an infinite number of decimal places.

[Samper]

Are you an M.I.T grad? Wouldn't surprise me at all. ;)

[Ninong]

Are you an M.I.T grad? Wouldn't surprise me at all. ;)

No, but I happen to know that three point one four one five nine is part of a little jingle that they sing at M.I.T.

[middlemark]

Thanks for all your responses. I found a 6 quart container with accurate measuring marks at a restaurant supply store for 3 bucks (should come in handy for other things too).

Probably a good thing for livestock acclimation too ... that's what my `measuring' container does in it's free time.

I dunno about sharpie. IMO, it would be the one I would choose - but yet don't really `know'.

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And thanks to all for the calculation info ... a math review is needed every few years personally. Where were all the reef-based `word problems' on my math tests as a kid? I would have aced them ;)