SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

I took the pruning shears to this thread because my answers got cross-pollinated with another pump matter.

Anyway, if you can't get a pressure relief valve to open as much as you want to, at some pressure of your choice, and still have it staying completely closed at system operating pressures, the response from pressure relief valve manufacturers is "so what" because the pressure relief valves you see are intended for protecting multistage submersible pumps. They simply don't snap fully open. They open gradually while pressure rises another 10 psi or more. All you can do is fiddle with the thing, or buy one or two more and see if they work any better for you. For what it's worth, even a fraction of full pump output is good enough protection.

Forgot to ask this:

I'm interested in thermal protection. All I see on the sprinklerwarehouse site are the smart box relays, which are more than I want to spend. I looked locally at a few places (like Home Depot) but either they don't have something or I'm not looking in the right place. Do you have any recommendations? It appears that the new pumps have an internal thermal protection system. My pump is 20+ years old Red Jacket pump, so I don't know if it has this protection.

I have not spent any money on a PSV or the relay yet. (I had the relay last year when things worked).

OK, I understand that the jet pump recirculates. Maybe I'm not being clear, but IF I had a centrifugal pump...say 1 HP, shut off pressure of 45 psi. I hook it up to my pump relay controlled system. Out of the 50 or so people in my area that have a point well and sprinklers, seriously 1 has pressure tank. They can't all have this issue. Anyway, wouldn't my hypothetical 1 HP centrifugal pump have the same issue I'm having now? If the shut pressure is 45 psi, I'd get a PSV in that neighborhood, but if it dead heads for 2 sec before the valve opens, it won't really do me much good...

If you read a good jet pump tutorial, you would already know a jet pump recirculates a portion of the water it pumps.

For the time and money spent messing around with the pump relay and pressure relief valve, you could already have a pressure switch and baby pressure tank controlling pump operation.

I wasn't asking the difference between the pumps, I'm asking why you said I don't have the "head room" because I have a jet pump. Either way, if it's a jet pump or a centrifugal pump, it will be momentarily dead headed and will produce it's dead head pressure. Whether its 60 psi, 40 psi or 100 psi. I would like to get a PSV and set it for just under my dead head pressure so in the even that a valve fails the PSV will open and protect the pump. You say that a PSV is not a good idea for a jet pump. You mentioned that my shut off pressure is 65 and I operate at 60 - I don't, the pump operates normally in the 40-45 psi range, with the valve open.

What I'm really getting at is this: I see people recommend to others to have a PSV on their system. In a case like mine, where the pump is momentarily deaded head and produces deadhead pressure, how can you ever size a PSV that will open when your valve fails, but not everytime you start the system because the zone valves don't open fast enough.

And, I did read the tutorials. I googled stuff. Alot. I'm a chemical engineer and I work with pumps and piping systems everyday at work. This issue I am having is pissing me off to no end because I cannot figure it out. I wish I could just delay the pump relay from starting by 2 seconds and life would go on.

I think you need to google some of these phrases and spend some quality time reading tutorial pages.

Ok, then what is the difference between my jet pump (it operates about 40-50 psi, just it has that 2 second 60+ psi period when it's dead headed) and a centrifugal pump? Either way the pump will be dead headed and running for a period of time before the zone valve opens.

"headroom" means you can operate the device effectively - a jet pump running at 60 psi with a shutoff pressure of 65 psi gives you insufficient headroom for a relief valve, compared to a deep-well submersible pump with a shutoff pressure of 190 psi

a pressure relief valve opens gradually as pressure rises, instead of snapping open like a switch - not good protection for your jet pump

Ok makes sense. Care to explain what you mean by "headroom"?

you are describing a bolt-on ejector assembly - all jet pumps have an ejector - so-called Shallow Well Jet Pumps have the ejector built into the pump - Convertible Jet Pumps use the separate ejector assembly