How much GPM is my pump producing?

[mas985]

If the 30 PSI you gave is with solar, then you have excessive return head and you cannot use the approximations given earlier. So your head loss is probably closer to 80 feet than 90 feet. This would result in about 70 GPM which gives you a turnover of about 2.5 hours.

I think your run times are more than enough as long as the pool stays clean.



As for velocity limits in PVC pipe, here are a few good links:

http://www.engineeringtoolbox.com/pv...res-d_796.html

The above link shows the bursting PSI which is really the limit for PVC piping and not flow rates. The 44 GPM comes from a recommended velocity limit in PVC piping of 7 ft/sec. However, this is not a hard limit.


http://www.engineeringtoolbox.com/pv...oss-d_802.html

This one you can see that the head loss just increase with GPM. The table stops at 60 GPM for 1 1/2" pipe but the following links can be used to calculate head loss for any GPM.

http://www.engineeringtoolbox.com/ha...ter-d_797.html
http://www.engineeringtoolbox.com/da...ion-d_646.html

Engineeringtoolbox.com is a great site to learn all about hydraulics.

Here is one more that gives some background on the limits:

http://www.poolandspa.com/page825.htm#Hydraulics

Sizing

The running water not only encounters friction created by pipes and equipment, but the water itself is creating friction. This friction will strip copper from pipes and heater components causing all kinds of havoc,9see the section on chemistry, damages filter grids, and makes DE or sand inefficient (see the filter section).

Because of this, most building codes set maximum flow rates of 8 feet per second through copper pipe and 10 feet per second through PVC. Since heaters all use copper heat exchangers, use 8 feet per second even if the plumbing is PVC. Los Angeles County, for example, allows a maximum flow rate of 8 feet per second on suction pipes of any type. What is feet per second in terms of gallons per minute?

50 gpm in 1 1/2-inch pipe = 7.9 feet per second

50 gpm in 2-inch pipe = 4.8 feet per second

60 gpm in 1 1/2-inch pipe = 9.5 feet per second

60 gpm in 2-inch pipe = 5.7 feet per second

By the way, there are a few exceptions to the rules. Los Angeles County requires pumps to deliver the desired gallons per minute at 60 feet of head. When sizing pumps, you must assume at least 60 feet of head regardless of the actual calculations. In filters, on the other hand, you must use the actual head as measured. Altitude also affects these calculations. Over 3300 feet above sea level a motor runs hotter, so you will want to upgrade to the next horsepower.