new max-e-pro sta-rite pump & operating questions

[tenax]

well, with an automated pool vac coming that requires a minimum flow rate to operate ok and changing of furnace, new pipes and wiring change to 220 from 110 to come, i sniffed out a deal on a well rebuilt max-e-pro 1 hp pump on ebay. (my current pump is 3/4 hp and at least 8 yrs old and while working fine, it seemed a bit underpowered for my ballpark total head)

so, here is the situation:

new pump 1 hp going into 1.5 inch pvc throughout the system. if i understand the gpm curve correctly and can simplify, my total head based on the returns length from the main drain and the skimmer are a whopping 108 ft to my pool shed! (combined)

the 3/4 hp starite pump i have when vacuuming using the manual does require the main drain to be closed to add pressure to the skimmer and it seems to do a decent vacuum job.it can get enough suction to hold the vacuum head in one spot sometimes!

looking at the curve again, this pump based on both valves being open would do a measly 20 something gpm. (i don't get any cavitation with current pump unless there is air in the line) but when one valve is closed, it should kick up to about 60 gpm..a bit more than i need a given my sta-rite filter has a max of 62, a little tight..

so, here's my thought for feedback..i plan to use the valves to keep control on the gpm..i.e. simply for example..leave skimmer open, main valve half open..and i think i should be able to find settings that work for vacuuming..and at the same time are safe enough for my filter..i.e. i'm looking for the 45 to 50ish range.

does this seem to make sense? hope so, cause the new 1hp is bought and paid for..by the way, i have to say this was the best deal on the net, fyi. the guy gives a 1 year warranty, has 139 pos evals with no negatives so he must do a darn good job and i was able to buy a pump that goes for 350 plus new at the pool stores for 150 and shipping. (looking at other ones he's sold,they seem to go for between 120 and 180 depending on the brand and size) he says the motor in this is a new A.O. SMITH as well which i've heard is a darn good motor and the whole guts have been refurbished. if it's anything like my current sta-rite that's still going, it'll last a long time.

[duraleigh]

Tenax,

I am somewhat suspicious of your head calculation.....it seems quite high.

Mark (mas985) is the guru and I'll bet he sees your post and replies. He has a "rough" formula you can use to get pretty close on head.....I'm gonna' make a stab at remembering it.....I disavow all responsibility for getting it right!

Take filter pressure x 2.13 and add 10 for the suction side resistance. So, assuming I've got that right, your filter pressure would be 46psi.....I don't think a pool pump can get there.

In any event, I am clearly not a good resource for a definitive answer. Others will hopefully bail me out soon.

[tenax]

if you are referring to my 108, i searched the net trying to find a calculation that wouldn't involve measuring vacuum and such..i know it's ballpark for sure, but i got that suggestion from inyopools faq i believe it was that said for a "simple" TH calculation, add the length of all your returns to get the TH. then i went to the "curve"...maybe garbage in, garbage out at least as far as the TH, but i don't know how to derive it any other way that i "get".

a summary and more information if it helps includes:

15,600 gallon pool (u.s.)
a skimmer and a main drain.
1.5 inch piping everywhere.
1 hp sta-rite max-e-pro pump which i believe is supposed to develop in excess of 60gpm at TH of 50.
sta-rite sand filter max rated 62gpm
vacuum that requires a 1hp or 1600 gallons per minute flow, i believe it is.
4 -90 degree bends, 3-45 degree curves in the pump shed. (don't know how it was bent underground as the pool already existed)

[duraleigh]

Head loss is usually between 45-65 ft of head which means your flow is between 110-135 GPM. Your probably near the lower end given the size of the pump (higher head). If you want a better estimate then you need a more accurate head measurement.

Total Head = Return Head + Suction Head
Return Head = 2.31 * Filter PSI
Suction Head = 1.13 * Pump Suction (in. mg.)

If you can't measure suction head which requires a vacuum guage, use this formula:

Total Head = 3.2 * Filter PSI (assumes suction is 40% of return head)

I found Mark's post. So, if you take his simplified calc and use 108 as total head (108 / 3.2 = 33.75) your filter pressure (clean) would be around 33-35. Is it that high?

[tenax]

do you mean as measured by the sand filter pressure guage? i run about 15, 16 normally with the 3/4 pump since the day i started..when it's up to 20, it's definitely backwash time.

[tenax]

it did occur to me when figuring that 108 number that maybe i was supposed to take half of that? if i use 54 and do the division, it comes to 16 and change which is exactly what my pressure guage says on the filter.