See above in red.
Thanks Russ for the input. When you say that you should always have your overflow sized so that it can handle more flow than your returns, why is this so? Won't the return pump be the major determining factor for the amount of water getting pumped back into the display?
Yes, the return pump will determine the amount of flow into your display, absolutely right. However, 2 - 3/4" returns can handle the return flow of 600 gph EACH. That's where I got the 1200 gph from. The problem is that your overflow will not be able to handle more than 700 gph (that's what you mentioned). This is the reason you want to ALWAYS keep your overflow larger than your returns. If the pump is too large for the overflow it doesn't necessarily mean it is too large for the returns. Sending more water back to the tank than the overflow can handle means the excess water has only one place to go, over the sides of the tank onto the floor.
Where do you get your figure of 1200 gph for the dual returns? If I were to go with 2- 1/2" returns how would this affect the the gph? I was planning on putting a valve on each return so that I can adjust the flow as needed is this a redundant idea? Also I was planning for the inverts of the return lines into the tank to be higher than the invert of the overflow teeth.
My mistake....I thought I read that you were using two 3/4" Locline returns. As stated above, each 3/4" return can handle 600 gph. The flow rate for 1/2" Locline is approx. 400 gph. So two 1/2" return Locline can handle approx. 800 gph. This is much closer to your overflow of 700 gph and much safer.
Adding a ball valve to each 1/2" line will definitely help your design. Be aware that is just more backpressure on the pump causing you to have to upsize the pump that much more. Not a problem, just a factor you need to consider when sizing the pump appropriately.
Also the guys from GH said this when I asked if his 4-500 gph that he recommended is the rating of the pump or the flow at the invert of the return lines
"400-500 would be the actual flow rate, so head and plumbing losses would be considered"
The guys from GH are saying precisely what I'm saying. You need to consider the head (vertical lift) and plumbing (pvc backpressure) when you select the pump to adequately flow 400 gph through EACH of the two 1/2" Loclines.
I don't know why I am getting confused about this. I completely understand the theory of pumping more water into the display than the overflow can handle is a very bad idea.
This is what I am getting confused about:
When you said the above about select a pump to adequately flow 400 gph through each of the two 1/2" Loclines won't 800gph total flowing into the tank be too much for the overflow and result in a living room flood? This is the maximum scenario for the returns and being that the Eheim 1262 pump you suggested has a rating of 665gph at 4 ft split into two return gives you 330ish gph for each return which would not overwhelm the overflow but does not meet the 400 gph rate?
Do you want to try to keep your returns at max capacity? So then I would need a bigger overflow or smaller returns?
which seemed low when you factor in the head it must overcome, but I don't have much experience.
Hopefully the above explains it well enough to overcome your lack of experience.
With all that said, what alterations would you recommend for my design and also what pump (that doesn't produce a lot of heat and is very quiet) would you recommend. I wouldn't mind paying more for a really nice quiet pump.
Thanks for you input!
Once again, without knowing the actual vertical height and number of plumbing fittings (just going with past experience from our installations)
I think your two 1/2" Loclines at a height of approx. 48" should be able to handle an Eheim 1262 or a bit larger with a Marineland Euro Utility Pump 4500. Both pumps are quiet, efficient and can handle the job.
Hope this helps,
Russ
I have decided to go with the 700 gph glass-holes overflow and I am pretty sure I am going to do 2- 3/4" lockline returns also from GH. (Overflow will be in the middle and returns on either side.) I will be using 2- MP10's in the display so I am not relying heavily on the returns for flow. I emailed the GH guys and asked him this questions a couple of times and got a vague confusing answer each time so I figured I'd ask it here:
