Max water flow for drilled hole in aquarium

badmeowth

Reefing newb
I have a 65 gallon tank and just brought it in to get drilled. I am planning to get a 1.5" inch drainage hole with a skim box included. About to get a return pump for the sump and wondering what is the maximum drainage capacity of a single 1.5" inch hole. Tried searching the internet for max gph of various hole sizes but to no avail.

Thanks!
 
I believe 1" is about 600GPH so i would say a 1.5" is roughly 900GPH.

Someone will confirm this, i personally dont have a drilled tank so im going on my memory for this one.
 
Your maximum drainage through a bulk head is going to depend on chiefly where it is located and what is introducing the water into the bulkhead hole. Back of the tank flow rates are different from bottom of the tank flow rates for the same diameter hole. Mega flow or Durso entry into a standpipe inserted into a bulkhead produce different results. A safe and sane assumption is that you will achieve approximately one half of the maximum flow as advertised by the aquarium manufacturers. As for anyone saying a 1.5 inch pipe will only flow a half again more: a 1.5 inch diameter pipe or bulkhead has just over seven square inches of flow area and a 1 inch has 3.14 square inches of flow area. Plus a larger pipe loses less flow potential than a smaller pipe due to its surface area being proportionally smaller. A safe estimate for a bulkhead flow through rate is around 300 to 450 for a 1 inch and 750 to 900 for a 1.5 inch. Basically a 1.5 inch will flow over double a 1 inch. The only way you will consistently receive the rated flow of 600 gph through a 1 inch hole is if there is an constant siphon going on, or put a hole in the bottom of the tank with no pipe above the hole, however that is definitely not advised unless the drain runs to a closed loop circulation system pump. Remember most people are only getting about 60 to 70 percent of the rated flow of their pumps back into their tanks, so an overflows capacity can not be judged by a pumps capacity with no head or friction and few people actually calculate the losses that their pumps will experience from head heights and friction. I do engineering *rap so I do calculate my pump losses to include using pump curve charts supplied by pump manafacturers.
 
thank you for the detailed insight , i found it very helpful.

i am planning to buy a return pump in the upcoming days and were wondering which brands were reliable and how much pump capacity to look for assuming I have the 1.5" hole drilled on the back glass pane (near the top with skimmer box). The pvc will run directly into the sump, with no T joints, etc. I was recommended by the lfs to look for 400-500 gph and definitely no more than 700 gph, not including head height loss
 
If this return pump is for in-sump application then a Mag 9.5(950gph) would be a good fit.At about 4 ft. head height it will only push 500gph or maybe even less.Don't forget a ball valve on the return end for added control over the flow.

I like the Panworld 100PX(800gph) external water pumps.It doesn't loose as much flow at 4ft. head height as the Mag.It should be somewhere around 500gph as well.
 
Your overflow box will most likely dictate the rate of flow. You only want the water level to be a max of 30% up the sloted holes for your over flow, or not more than the overflow can handle. (Fatman is right on) good luck.
 
Unless the pump is going to be used for some additional function, such as circulation through a filter or chiller etc, I would get a circulation pump and not a pressure rated pump such as the 100PX. That is assuming your sump is right below your tank. I also like a Pan World Pump as it is almost as good as an Iwaki. A little warmer to the touch and a little louder, but not extreme considering the 25 to 30% difference in price. I would choose the 50PX-X, which is rated 1110 gph at 90 watts. You might have to throttle down the flow just a little if you put in a really clean return piping system, but that does not happen very often. Figure on around 900 to 959 gph with a typical PVC pipe installation and 800 gph with a vinyl hose installation. For a clean PVC installation, thats talking straight cut pipe ends, deburred and double 45 degree fittings instead of 90 degree and true "Y" fittings instead of "T" fittings, and ball valves, unions, plus valves for balancing branch return lines if yoy used "T" fittings instead of true "Y" fittings. If will be a large enough pump to allow you to branch your return into two 3/4 inch or four 1/2 inch return nozzles which could pretty much eliminate your need for in tank obnoxious power heads. If you really want to get into it I can talk you through a whole system, with maximum flow and maximum return volume with medium velocities. Just in case you want to get heavily into corals rather than fish. :bounce:
 
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