Sizing sprinkler zones for water well pump

Question

I live in central Oklahoma and we bought a 40 year old house which depends on well water. In 2017 the pump was serviced and a new pressure tank, pump controller, and pressure switch were installed. In March of 2019 we had sprinklers installed, 6 zones in all with 6 heads on most zones. 3 months ago I had to replace the pressure switch (contacts were burnt up), yesterday I replaced the pump controller (bad start capacitor), and today realized the bladder in our pressure tank has busted... fun.

In my research as to WHY all of this has happened I came across several articles and discussions and it all boils down to the pump cycling on/off too frequently. In my case, when the sprinklers are on the pump cycles anywhere between 45 and 90 seconds depending on which sprinkler zone is on. I realize having a busted bladder is going to impact the cut in/out times, but I don't know how much of an impact it will have when watering the lawn. I figured that is more about stuff in the house like faucets, toilets, etc... since sprinklers will burn through 20 gallons of drawdown (80 gallon WF-23) in no time.

From what I've read the, sprinklers should be right-sized so the well pump runs continuously while they are on. This means that each zone should have the same output in gpm as the well pump. Does that sound right? If so, should the company who installed my sprinkler system have known that? I'm not looking to recoup any sort of payment from them for the broken well components, or my time to fix them. I'm simply curious if this type of thing is something they should have accounted for. If so, I'll likely ask them to come right-size the sprinklers so once I get this bladder fixed I can feel comfortable running my sprinklers without ruining my well pump and other components.

Also, I have read about Cycle Stop Valves and I'm considering installing one to help with all of this. It's just a bit complicated since they spliced the sprinklers into the main line before it goes into the house. Apparently I must install the CSV before that split... not sure how I'll achieve that just yet.

Thanks in advance for any help or advice!

Answer 1

This means that each zone should have the same output in gpm as the well pump. Does that sound right?

I'm no expert, but not to me it doesn't.

According to that logic, you need to somehow match the sprinkler flow exactly to the well pump flow. If the pump flow is just a little too low, eventually you run out of pressure. Just a little too high, and you're back to cycling the pump.

It seems to me that the well pump system should be durable enough to accommodate the irrigation usage. I certainly don't see any reason that the cycling would cause the pressure tank bladder to fail, and the pressure switch and controller ought to be good for many years of cycling, even under irrigation conditions.

I'm not clear on why the whole controller was replaced, if all that was wrong was a failed capacitor. Capacitors are cheap compared to the expensive components they're part of.

If the component are old and/or were never very high quality to start with, I can see how usage, irrigation or otherwise, would lead to failure. Maybe time to just put in better parts.

If you do go that route, consider a variable speed pump, which should be able to come close to matching the exact irrigation flow as needed, significantly reducing cycling of the system. Higher quality parts should be more durable in any case, and using a variable speed pump would mitigate or eliminate any concerns you might have about frequent cycling.

As far as the cycle stop valve goes…

As I understand its mechanism, it closes down (reduces) the output of the well pump before the pressure tank, preventing the system pressure from getting high enough to shut off the well pump. So instead of allowing the well pump to deliver water at its usual rate, with the pressure tank serving as a buffer to accommodate excess flow, the well pump is constantly working against the valve, delivering a higher pressure than is allowed to exist downstream of the valve.

I know that in the extreme example where a well pump is allowed to run without any water moving through it, the pump will quickly be ruined. Use of a CSV would not be nearly that bad, but it still means that the pump is not moving water as quickly through it as it's designed to do. I would expect this to cause the pump to work harder than expected, and possibly dissipate heat less quickly than designed, potentially leading to premature failure of the pump.

That said, if you do a web search like "do cycle stop valves damage pumps" (Google suggested that), there are lots of sites that vehemently defend the use of cycle stop valves and argue that they will improve the lifetime of the pump.

So if you can figure out a good place to access the water line between the pump and the irrigation line where the CSV needs to go, that could be a good option. Certainly if you're amenable to installing a CSV, this will accomplish much the same result as a variable speed pump, and is a far simpler approach than trying to somehow match your irrigation flows to the pump itself, the challenge of finding the right place to put the valve notwithstanding.