Question on pump size.

[rhomer]

This is a little after the fact, but I have a 90 All-Glass pre drilled. I've been running a mag 5 and decided it was time to upgrade. So I purchased a mag 9.5. According to All-Glass's web site, the overflow will handle 600 gph (2400 gph rated pump at 5 feet of head). I would suspect I should be fine, but does anyone here have a mag 9.5 on their 90?
Rob

 

[squidd]

With 3/4"eturn line, you be ~648gph return and pushing the limits of the overflow, but it should work...
If it's too much replace with 5/8" return line...or put a "T" on the outlet...

 

[rhomer]

Any idea what they mean by (2400 gph rated pump at 5 feed of head)? I read that to mean that pump ratings are grossly over rated.

 

[scsinet]

It means that the pump can handle 2400gph when lifting water 5 feet vertically. Most pump's raw GPH is assuming 0' head, which obviously is not realistic in any return pump application. You have to measure from where your pump is to where the return jets are. Add about maybe 20% for your elbows and other things that slow things down and you have your head. Most mfrs provide a chart for each model that lists their GPH at a given head.
... oh, and incidentally, I run a mag9 on a 55 system with a 600GPH overflow and everything works just fine, so I think you'll be okay. I have a 4-5' head on my system.

 

[jessecnc]

All-glass does not mean use a pump rated for 2400GPH at 5' head. That would be 2400GPH return to the tank with a 600GPH overflow. The result would a lot of water on your floor and a burnt pump. What they're trying to say is to use a 2400GPH pump, so after a 5' head and plumbing you'll be at 600GPH! They are in a way assuming that pump ratings are over rated.

 

[rhomer]

Yeah I've seen the mag pump chart and it states that at 5' of head the pump's performance is 750 gph. Then I read the all-glass ratings and wondered if the pump manufacturers are either a little full of themselves or that the calcs that we use to determine flow is different then what all-glass is using.
My guess is that there is a little dirty secret behind these values that the pump manufacuters publish. I suspect that the values are more like what all-glass stated. This is where it would be cool to have the time and funds to run a quick test on an overflow rated at 600 gph and a few pumps to determine exactly where the tank overflows and the sump runs dry.
BTW thanks SCSInet that was exactly what I was looking for. :joy:
Rob

 

[squidd]

(2400 gph rated pump at 5 feet of head).
Some of that "confusing" number comes from the fact that their returns are only 3/4"...very restrictive...and accounts for a"lot" of additional head pressure...
Pumps are for the most part rated (on their "charts") with 1" line..kind of an industry standard..
So 2400gph - 5' head thru 1" (depending on pump) drops off conciderably when reduced to 3/4"...
But even then, the numbers are a bit "skewed"...
My thought is ...it's a typo and they ment 2400 "liters" per hour..at 5'...which is much more reasonable...
I'll try to contact "Tech" and find out...those boys love talking to me...

 

[rhomer]

To close out this question. I hooked up the new pump with 3/4" return and 1" for the overflow. The overflow seems to work fine. A couple of observations:
1) The overflow seems to rise and fall in a rythmic pattern about 1 inch. (wierd)
2) The sump seems to burp a lot. I put a 90 degree elbow at the bottom and quieted the burp down a lot.
3) There is a HUGE difference in the amount of flow from the mag 5 to the mag 9.5.
I hope this helps anyone going forward on gauging pump size for a 90.
Rob