Couple things about pumps

I have been reading a lot of posts about people having questions about flow rates out of their pumps, and since I know a little bit about this subject I thought I would start this thread to maybe save some members a lot of agro and perhaps some money as well.

First of all, none of this has anything to do with the art of fish-keeping or proper aquarium setups or anything of that matter...I am not really even a newb yet, what's lower than newb, wannabe newb? All this is about is the mechanical workings of the common styles of fluid pumps used for most home tank purposes.

First of all, these pumps are lubricated by the fluid that they are pumping, in this case water.

Second, the impellers operate by filling up a cavity with water and rotating very fast forcing water out of the cavity. The further up that you have to pump it, the more weight there is to pump against (more water in the pipe means more mass which means more downward force), which causes the flow to lessen.

The head rating that most pumps come with means that at full capacity, you will get the rated GPH out of a hose that is the same diameter as the output of the pump at the vertical height that corresponds to the head rating.

OK, heres the important stuff. Full capacity means that you are supplying the pump all the water it can pump. Every time that you restrict the lines by adding an elbow or a a bunch of twists and turns in the hoses, you are causing less water per time to get to the pump. This in itself isn't so bad, a 1 inch drain can output something like 12000 GPH, but when it comes to restricting the input flow with valves you may be causing your pump to operate without the proper lubrication and therefore break down much earlier. Same principle as running your car engine with no oil.

Limiting flow on the output can also cause issues, more heat generated, more current through the coils of the motor...all of which also take their toll on the equipment. IMHO, if you absolutely need to restrict your flow, and most of us will probably either want to or need to at some time, restricting the output of the pump is the better of the two options. The best option is to match your pump as closely as you can to the conditions that you need.

There are a number of good articles in the 3reef forums that have been posted about this already, and Google has a ton as well, but you need to be a physicist to make much sense out of most of them. This post is meant to put it in (hopefully) easier to understand terms, and I'm very sure that the veterans on this site already know all about this stuff.

I am just trying to help the people out there who might want to go out and buy a 9 Giga-GPH pump because they may get a larger setup one day, only to see it melt into a pile of sludge, or wonder why their 300 GPH that's plumbed two stories below the tank is barely trickling.

Hope this helped someone,

Peace!

 

Good write up. Certainly helped me. I know about the animals, not the equipment, so this was actually very helpful. Thanks, and a late welcome to 3reef.

 

Thanks LCP