Return to the Irrigation Forum
| Post a Follow-Up
New well, Is 15GPM enough?
| | |
Posted by ramor (My Page) on Mon, Nov 2, 09 at 13:20
| I just had a well installed and I didn't realize before the install that I would be getting only 15GPM with a 1-1/2HP pump. The well is 218 feet deep and the outlet pipe is 1-1/4". The well is constant pressure with a cycle stop valve. I plan on having an irrigation system for between 3/4 - 1-1/2 acres and it will be zoned.
I talked to the installer today and he said he could up the pump size to a 2 HP but he would have to check to make sure the wiring size and the pipe size would accomadate the larger pump. He also guesstimated that it would cost me an additional 5 to 6 hundred and it would give me in the neighborhood of 20 GPM flow.
Do I need the larger pump or should I just stay with the 1-1/2 HP pump?
Thanks |
Follow-Up Postings:
RE: New well, Is 15GPM enough?
| | |
| Ram, What is your water demand (gpm) for what you will need for your 1 1/2 acres? Do you have an irrigation plan? How many zones? What is the max flow that the biggest zone will need? You have to look at the delivery side to make a call on the supply side. Aloha |
RE: New well, Is 15GPM enough?
| | |
| What is the well capacity? That is, how much water is the well capable of providing. You can't pull more water than the well is capable of delivering. Is 20 gpm the max that can be drawn? It seems we are missing some info here on the well. There are 1 1/2 HP pumps capable of delivering 20 gpm, so I'm assuming there may be a reason he wants to go to a 2HP???? We do not have enough info to give you a good answer. By the way, a 1 1/4 delivery pipe is plenty big for 20 gpm flow. The single most important thing you have to watch in setting up a irrigation system off a well is to be sure that you can run it for the many hours needed without drawing the water level down to the point where it adversely affects the sprinkler operation. A good well guy should put you on the right track. |
RE: New well, Is 15GPM enough?
| | |
| I've been flip flopping today on what to do about this. I've got a good well guy and the 15gpm will probably work OK for the sprinklers a zone at a time. I still think I may go with the larger pump if he believes the well will produce enough. I hate not having good water pressure and the master shower will have multiple heads which can probably draw 10 GPM. If someone else is running water in one of the other tubs or showers I think I could be on the edge at 15GPM. I'm sure a bit of extra capacity would also help the sprinklers. Thanks for the advice. |
RE: New well, Is 15GPM enough?
| | |
| ram, I might add your demand side should be 80% of what you need from your well. So if 15 gpm is your max demand then you need to produce 18-20 gpm from your well. Another idea is to put a pressure tank filled by your well that could supply your house and yard for 12 hours and fill the tank 12 hours. The well guy could calculate what demand you might need and the size of the tank as well. No pun intended. Aloha |
RE: New well, Is 15GPM enough?
| | |
| Ok, I might be a bit out of my lane here but what about a cistern or holding tank that would feed into your irtrigation setup. The tank can easily be filled while you sleep and you'd have zero impact on household water supply when running your irrigation. |
RE: New well, Is 15GPM enough?
| | |
The gpm is only relevant if it is the sustained yield gpm.
Most wells produce higher gpm upon start-up, but can run dry after a period of time if it can't replenish at the same or higher rate . A system should be designed on 80% of the wells sustained yield gpm to be safe.
I have designed systems with that gpm that work great. You will have to make adjustments in the design, and not every irrigation contractor knows how to design systems on a well with limited output. Ask questions!! Your question re: the motor size is also relevant to the Sustained yield of the well. |
RE: New well, Is 15GPM enough?
| | |
| I don't have enough info to be sure here, but I'll take a pot-shot and just say: If your system isn't relatively large, 2 HP is over-kill. Especially if your system can't actually TAKE that kind of pressure, it will cause more resistance on your pump and eventually, will burn it up. It can also blow smaller systems up to have too much pressure. Consider the cost. More HP = More $. |
RE: New well, Is 15GPM enough?
| | |
I'd love to run 35 gallons a minute here but my well permit limits me to 17. I designed 12 gpm(80% of 15gpm) into the irrigation system but can easily move to 35 should I ever get an allocation/adjudication for an irrigation well.
For now I don't push my domestic well as it also feeds the house.
To answer the op, I would stay with 1.5 hp. You could irrigate at night when your multiple head shower is idle.
Peace |
|
|
|
|
