Hehe, yeah my boy likes to build along side of me, I can see him becoming a tinckering fool like myself..
Well, I was looking hard at my small 3/8" ID barb on my graduated high tech trash can, so I upgraded the inlet to a 3/4" barb and radiused the inlet and added just enough 1/2 tubing to attach the pump so I'm as close to free flowing on the inlet side as possible.
The pump alone without any tubing got 6.69GPM this evening with 3 runs so at the far right of the curve it doesn't take much pressure drop at all to hurt flow rate. This test is a little flawed because I'm actually gaining on average about 1' of head pressure from the measuring can fill level. When I test with a piece of tubing at the outlet, I can correct for it by ensuring the end of the tubing outlet is at the same elevation as the water level dropping, so this flow rate is likely a bit higher than a pump with an inlet that has 0 pressure head. So I ran the test again with the improved inlet and one 14" piece of tubing and got 5.9 GPM, so the actual free flowing would be somewhere in between 5.9 and 6.7, probably something closer to 6.2 to correct up for the piece of tubing that is causing some pressure drop...it's very sensetive at this end.
I also did my first max head pressure test using two 10' sections of tubing like this:
The pump was able to lift the column of water right up to where I have it wrapped around the branch, so there is no way I'm going to be able to measure max pressure head of two pumps in series...I will however run the test a couple of times to get a good average and do the same for the slightly weaker non-variable.
I also got more max head than swiftech notes, I got 13.8' (+- 3" of less than perfect measuring, had to drop a tape a long way down to the reservoir level) 13.8' of water is pressure head is equal to about 6.0 PSI.
I didn't quite expect that high of head, but then this was at the above 5 or max setting. I'm not sure what effect the mod had on the pump max pressure head because I never measured it prior, regardless I'm happy...almost 14' is good.