I would recommend using the mfg recommended discharge pipe inner diameter. Any bigger and you could actually decrease the amount returned to the tank. The pump curve is based on head pressure, which is essentially the weight of the water in the pipe that needs to be pushed up and over.
I thought the same thing until I was recently corrected by someone on here. What you wrote here (although it seems logical), is actually incorrect. Larger plumbing will never decrease your return pumps flow, but smaller plumbing can. Taken from the link I referenced above:
One of the really hard to grasp principles of hydraulics is the relation of volume of flow, pressure, and the weight of water. Odd as it seems a larger pipe will actually be easier for the pump. Its not the volume of water, but the height it is lifted that matters. In a way this is a variation on the old saying which weighs more, a pound of feathers, or a pound of lead? Obviously both weigh a pound! This version could be phrased which is easier for the pump, 5 GPM in a 1/2″ pipe or 5 GPM in a 2″ pipe? Neither because 5 GPM is still 5 GPM regardless of the pipe size! Yes, you would need more power if you were actually lifting more water, also we would need more power to lift the water higher, but neither is not what is happening. The amount of water nor the height we are lifting hasnt changed.
The other issue here is flow through a pipe. This is the issue that actually makes the smaller pipe potentially worse than the larger. Because the smaller pipe is smaller it is harder to force the water through it. The resistance of the walls of the smaller pipe causes pressure loss as water flows through. this is commonly called friction loss. How much friction loss occurs depends on the flow rate and pipe size. Both higher flows and smaller pipes sizes result in greater friction loss. This is the only reason a smaller pipe would be worse than the bigger pipe. How much worse is dependent upon the actual flow rate and pipe size.
As a general rule (ie: not always true, but is most of the time) the pipe size of the pump outlet is almost always smaller than the size of pipe that will provide optimal flow from the pump. In other words, if a pump has a 1″ threaded outlet, it is very likely that a 1 1/2″ pipe would be attached to the 1″ outlet for use as the outlet pipe. Pump manufacturers tend to use smaller size inlets and outlets to save money.
so i found out the tank i want to buy when it comes onsale every summer typically, is the 300gal deep marineland tank... which has the drains drilled on the bottom of the tank it self, and allow for 700gph each for a total of 1400gph...tank dimensions are 72x36x27 reg $1899 on sale at $1399
http://www.marineland.com/Products/Glass-Aquariums/Deep-Dimension-Corner-Flo-Aquariums.aspx and im kinda unsure what these is they are listing that comes with the tank "dual Loc-Line[SUP]®[/SUP] outlet nozzle
s"
i figured a pump like this would prolly be perfect at 88watts and 1800gph@12ft max head height (same place id get the tank from)
http://www.incredibleaquarium.com/i...oduct_info&cPath=201_190_253&products_id=2294 OR i can go with the laguna pump but it 100watts
http://www.petsandponds.com/en/ponds-and-supplies/c5816/c209861/p16438658.html
what you guys think ?
Here's a pic of Loc-line:
Sounds like the two drains that come standard on the tank are 1". I would see if having the holes expanded to 1.5" is possible. I don't know why, but most mass produced tanks come with really small drains. Larger drains give you a lot more flexibility.
Here is a breakdown of some pump options:
The WaterBlaster 7000 will give you 869GPH @ 6' of head pressure drawing 88 watts (efficiency = 9.9 GPH per watt)
The WaterBlaster 10000 will give you ~1300GPH @ 6' of hed pressure drawing 125 watts (efficiency = 10.4 GPH per watt)
The Laguna Max Flo 2000 will give you 1373GPH @ 6' of head pressure drawing 100 watts (efficienty = 13.7 GPH per watt)
Both WaterBlasters and Lagunas are great pumps; you can't go wrong with either one. It just depends on the turnover you want and which pump is more efficient at your system's head height. If I were in your shoes, I would go with the Laguna 2000 which gets you close to your drains maximum capacity and a bit more efficiently than a comparable WaterBlaster (the 10000). In addition to being more efficient, the Laguna is also quite a bit cheaper. I would put a true union ball valve on the return line (
http://www.bulkreefsupply.com/cepex-ball-valve-1.html) for ease of pump maintenance and to be able to valve the pump back if necessary.
Hope that helps.
lol....
