Question

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Followup To

Question -
House on lake with old irrigation pump house that is 5ft above water and 10ft from the lake. The highest zone will be 50ft above and 100ft away from the pump house. I think my largest zone would have 10x 1.65gpm pop-ups, for a total 16.5gpm + plus my neighbor would like to run a garden hose so I'm guessing I need 20gpm at 50ft of head. Problem is I can't figure out what size pressure tank or pump to get - I've been looking at the 1.5hp flotec fp5172 and the cast iron fp5242 and a 42 gal precharged pressure tank.

Is that enough or too much?

Should I get the cast iron or the corrosion resistant pump for lake water, I plan to drain it every winter.


Answer -
Eric,you need at least a 2.0 horse pump. Pressure tank OK. Obvouisly the corrosion resistant better,but what is the price difference? Jim

Jim,

The corrosion resistant pump ($240) is cheaper than the cast iron by about $50 but the cast iron has more power and appears easier to repair in that the entire motor and internals can be removed without touching the pipes.

Regarding the pressure tank, I've read conflicting information about using either a really small tank (6 gal) so the pumps runs continously or getting a bigger tank so it has a rest.

Answer
  Eric,
 I kind of gave you a quicky answer last time and I'm glad you got back. I'm swamped at work and I was swamped with questions a couple days ago. I think it's got something to do with the weather??
I think I am right in assuming that the system runs on a pressure tank/pressure switch and there is not a wire running from the controller to the pump that turns it on when the timer tells it to from the pump terminal. So you need a pressure tank. The larger the pressure tank the less the pump has to turn on and off or short cycle. Short cycling the pump wears it out prematurely, so the larger pressure tank is the one to choose. Also if you've got the hose thing going on the larger pressure tank is better.

Also when I told you to go with the 2HP pump I did not ask what the power going to the pump is. If it is 110 VAC then you will probably have to stick with the 1.5HP pump. It's hard to find a 2HP pump that will run on 110VAC.

I know this can get confusing, but once you go over 2.0 HP on the pump you should have 220 Volts to run it. To get 220 to the pump you need to run a bigger wire (12/14 gauge), depending on the length of the wire run.

So, to keep it simple, go with the big tank, stick with the 1.5 hp pump unless you got the 220 already there and go with the cast iron since maintenance seems to be easier.

By the way, that's a hell of a good price on those pumps no matter what you choose and let me know if something changes. Jim