How to Calculate GPH?

[shawnriv]

Hello All:

I added a UV sterilizer to my new build and the return pump is feeding two returns nozzles. I plumbed the tank with a T going to one return nozzle and the other going to the UV sterilizer (which then comes out the other return nozzle). Two gate valves are controlling the flow to one return and the other to the sterilizer.

***I'm having a hard time describing my return setup, so I apologize for any confusion.

The UV I purchased recommends the GPH below. My question is, how do I calculate the GPH that's coming out of the UV sterilizer return? Is there a calculated formula I can use?

• Algae & Bacteria Water Flow Rate: 472GPH/788GPH (Suggested*/Maximum)
• Protozoa Bacteria Water Flow Rate: 79GPH/131GPH (Suggested*/Maximum)

Thanks so much!

 

[DCR]

No great way to calculate. You can temporarily divert the return into a bucket and measure it that way but since it is going to the tank you need to break it near the tank and keep the elevation the same. I would suggest shutting down the return pump and then emptying some water from the tank back into the sump (as much as the sump will hold). Measure the drop in the water level of the tank from normal (or the increase in the sump level). Shut-off the other non-UV return and then turn on the pump and measure the time it takes to reach full level in the tank. Multiply the change in level in inches by the cross-sectional area of the tank (or sump) - length times width in inches to get the total volume of water moved in cubic inches. Convert to gallons. One gallon equals 231 cubic inches. Then divide by the time to refill the tank in seconds and multiply by 3600 seconds per hour to get the gph. This is approximate because the other return flowing will reduce this flow somewhat.

Other alternative is to purchase a flow meter.

 

[shawnriv]

No great way to calculate. You can temporarily divert the return into a bucket and measure it that way but since it is going to the tank you need to break it near the tank and keep the elevation the same. I would suggest shutting down the return pump and then emptying some water from the tank back into the sump (as much as the sump will hold). Measure the drop in the water level of the tank from normal (or the increase in the sump level). Shut-off the other non-UV return and then turn on the pump and measure the time it takes to reach full level in the tank. Multiply the change in level in inches by the cross-sectional area of the tank (or sump) - length times width in inches to get the total volume of water moved in cubic inches. Convert to gallons. One gallon equals 231 cubic inches. Then divide by the time to refill the tank in seconds and multiply by 3600 seconds per hour to get the gph. This is approximate because the other return flowing will reduce this flow somewhat.

Other alternative is to purchase a flow meter.

Oh wow, that's making my head spin a bit. Lol. And...I definitely not interested in purchasing a flow meter and having to plumb it into my system. I thought about diverting the return into a gallon bucket (as you mentioned) and keeping it level with the tank. Then time how long it takes to fill the 1G bucket. For example, lets say it takes 20 seconds to fill one gallon.

20 seconds for 1 gallons = 1 minute for every 3 gallons
1 minute for 3 gallons = 60 minutes is 180 gallons
180gph?

Then I can adjust the flow with the gate valve to get to around 80gph for fish health (protozoa bacteria).

Just thinking out loud.

 

[DCR]

Oh wow, that's making my head spin a bit. Lol. And...I definitely not interested in purchasing a flow meter and having to plumb it into my system. I thought about diverting the return into a gallon bucket (as you mentioned) and keeping it level with the tank. Then time how long it takes to fill the 1G bucket. For example, lets say it takes 20 seconds to fill one gallon.

20 seconds for 1 gallons = 1 minute for every 3 gallons
1 minute for 3 gallons = 60 minutes is 180 gallons
180gph?

Then I can adjust the flow with the gate valve to get to around 80gph for fish health (protozoa bacteria).

Just thinking out loud.

That will work and is probably the best way if you are willing to break your connection to the tank

 

[fish farmer]

Oh wow, that's making my head spin a bit. Lol. And...I definitely not interested in purchasing a flow meter and having to plumb it into my system. I thought about diverting the return into a gallon bucket (as you mentioned) and keeping it level with the tank. Then time how long it takes to fill the 1G bucket. For example, lets say it takes 20 seconds to fill one gallon.

20 seconds for 1 gallons = 1 minute for every 3 gallons
1 minute for 3 gallons = 60 minutes is 180 gallons
180gph?

Then I can adjust the flow with the gate valve to get to around 80gph for fish health (protozoa bacteria).

Just thinking out loud.

That's the way I measured low flows like that.

You should have 1.33 gpm of flow for 80 gph. So filling a gallon bucket should take 45 seconds. If you have smaller measuring containers you could factor for quarts.

Check my math though...