DIY Skimmer talk

[Matt.D]

I was wondering, since I plan on doing a DIY Venturi Skimmer, I would like to know if you think that the more GPH your pump is, the better the skimmer, or that you should only have the total amount of water pass through the skimmer two times a day. (12 hours?) Which one would you think/know works better and for what reason? I need to finally know which way works the best! Thanks for your replys.

[specsgirl]

I think there's a fine line in the amount of flow you want going thru your skimmer. You need enough to get a good water return/cleansing ratio...but too much and you're skimmer isn't going to be as effective.

[Matt.D]

Thanks for helping me understand. With a 4" in dia. 3 foot tall skimmer with a 2" internal tube (venturi style) what would be a good GPH?

[fppf]

Skimming is all about contact time and flow velocity. So your GPH capacity will be ralated with the diameter and length the water moves in the bubble stream.

When I made my skimmer I started with how much I wanted to flow, about 1000 GPH. Then I sized everything to give a water velocity in the skimmer of .5 inchs per second and a 60 second total contact time.

[Matt.D]

Ok, since I'm lost and you know about it, would you please give me a guess on say a 4" skimmer thats 3feet tall? Thanks

[fppf]

Man, you kids these days :roll: (I can say that because I was told the same)

How about I help you and point you in the right direction. Everthing you need is on the internet. Its just some very simple math. You should know all the needed math, you just most likely need some help breaking the problem down into chunks you understand.

So lets start with flow, flow is a unit of measure, how fast a volume of something moves. Your asking for flow in Gallons Per Hour. There are 2 base units in flow, quantity and Time. So your quantity is gallons, but that can easly convert into cubic inches or any other measure of volume. Time can be hours, minutes, seconds. I think you should see where I'm going on how to convert GPH into cubic inches per second. The reason you want cubic inches per second will be apparent in a little bit.

Now, if you have a flow rate and you know what size pipe you want to squeeze it through then you will know the velocity. Velocity is another measurement, I quoted .5 inches per second. Again in this measurement there is distance and time. Now if you recall your flow is inches^3 per second it should be simple to figer the velocity. You know what size pipe you want, just figer out the area of the pipe in inches^2. Now if you take your flow of inches^3 per second and divide that by your area of inches^2 you get velocity in inches per second.

So there is how to calculate the velocity given a flow rate and a pipe size. You can shuffle it around to find any of those items.

Contact time should be real easy, its just how long the water stays in the pipe. So with .5 inches per second and if you want 60 seconds you would need 30 inches.

Now, how I got the .5 inches per second and 60 seconds was by looking at every skimmer on the market and seeing what there rates where. I got a range of .5-1 inch per second and a contact time of 30-60 seconds given the type of the skimmer. You can also do this, most mfgrs post what flow rates they support, the diameter, and the height of the skimmer.

On edit I forgot one thing, Google has one of the best online unit converters and math engines out there. If you type in a search "100 Gallons per hour to cubic inches per second" it will spit out the answer. So far I have not done a conversion yet that it did not work. It even gave the right answer when I had a typo and said, "don't you mean this?"

[Gryz]

Very good math lesson! :wink:

Sounds like a plan Matt!

[Matt.D]

haha, thanks alot man. Sorry for my crappy math..... I understand its frustrating to have to explain it all to me like that, I'm glad you did. You really don't know how much you just helped me!!! I finally know the best skimmers :D! Thanks man!


one last question though, that stuff above works for a venturi style skimmer with a smaller tube inside the main tube right?

[fppf]

Don't be sorry.
Just keep learning. I'm 26 and do work at a major aerospace company. I'm still learning everyday.

Just take a step back and break the problem down into its simple parts. Don't drown in the complex system, pick it a part. Remember "Kiss" Keep It Simple Stupid.

More than happy to help. Keep the questions coming and have fun with it. You learn 100 times more when you can apply the math to real world objects. I always hated math teachers that just move numbers around on the paper, who cares?