nfored;4311633; said:
You a mistaken and I can prove it. IF I plug one of the overflows guess what happens, the tank overflows. Why is that if like you said it flows the same? I will post a video since you clearly know what your saying and I am clearly mistaken. As far as flowing a certain amount of water your correct, but you fail to realize that my setup is a horizontal overflow so the 2 2" drains flow slower then the single pipe they are connected to because the pipe they are connected has a 20" drop making it flow faster.
As far as the 1.5 this might be fast enough for sure, when I said I would suggest a 3" is because if this being a horizontal overflow, which flows much slower. has very little drop then it will flow very slowly since there is no gravity. If you has a drop of like 10 to 20 inches then he could absolutly go with like a 1.5.
But why risk it if you look at the flow rate for 1.5 on horizontal overflow its close to 900gph. So what if he decided to upgrade to higher flow rate pump? or what if his drain gets partly clogged? Is it not better to go a little overboard for safety? I mean he is not going to be running this 3" pipe for a long distance, it would only cost like $9.00 more and be super safe.
Wow, ok, take it a little personally why don't you.
I would bet that if you were to completely remove one of the 2" overflows (practically impossible, although you could plug it, and then run new piping so only the one 2" overflow connected to the 2" drain pipe), that you could run a single 2" overflow, with a single 2" drain, and it would run perfectly fine. I'm guessing the way things are plumbed, there is an issue with turbulence causing loss of flow because of the dual pipes. Without seeing a picture of your setup, however, I don't really know why it would be that way. I'm simply guessing here, but since I've plumbed several large tanks, running higher flow than you do WITH horizontal runs, that maybe I could just possibly be on the right track. I am currently running dual overflows in my 125g tank, which are each handling over 800gph, with 1x1.25" pipe each. One of the drains runs horizontally inside the stand for 5 feet before dropping into the sump, and its running that volume of water just fine.
MOST aquarium setups that use a sump, have the sump housed underneath the tank. In that case, they are likely to have 20-30" of vertical drop, and anywhere from 0-6 feet of horizontal travel. That amount of horizontal travel (if only pumping 600gph), is NOT enough to need to increase the diameter of the pipe up to 3". As epond said, that is excessive.
The other problem with going to such large piping, is that with running only 600gph through it is going to cause it to be quite loud, as it will be splashing around the interior of the pipe more than it would in a smaller diameter pipe.
I also guess I don't understand what you're saying by "horizontal overflow". Unless you have a pipe sticking straight out the back of your tank that runs like 20 feet across the room before it drops down to a sump, it shouldn't have that large of an impact on the amount of water it can flow.
Here is the gist of what I'm trying to say:
for someone only running 600gph, anything over 2" is excessive. Anything over 3" is just an utter waste of money and piping, UNLESS he plans on upgrading to a much larger pump later, in which case it makes sense to install the correct plumbing now so he doesn't have to redo it all later.
