Why would well pump cycle on and off every second?

Quite the contrary - I've grasped one essential point that has obviously eluded you, with your purely theoretical understanding of residential water wells, namely that the surge hits 60psi (shutting off the switch) and drops back to 40psi, faster than the gauge can react. The apparent pressure shown by the gauge is not the actual pressure.

Your own criteria compel you to silence on this subject.

It's pretty clear that you have no practical, real-world experience with residential water wells whatsoever, and not much more in comprehending written English. [snip]

True, but utterly irrelevant - the clear sign of an academic with no experience in the real world. Who the hell uses a five-gallon pressure tank on a residential well? If you had any real-world experience with residential water wells, you would know that (a) forty-gallon and larger tanks - sometimes *much* larger - are the norm, and (b) *nobody* who has even the faintest idea of what he's doing installs and configures a residential well such that the pump kicks on after a drawdown of as little as gallon. One gallon isn't anybody's "rule of thumb" in the real world.

Go back to your ivory tower, and leave the discussions of real-world problems to those who have some actual hands-on experience with the equipment in the real world.

That would be a guess. Another guess would be that he simply failed to observe the brief flutter in the needle.

-jim

< There is fun in trying various things to see if < something can be made to work better but < there comes a point in development (well < systems for example) where further < tinkering is a dead end.

True in many situations but you'ld be surprised at how often you can find alternatives in "mature" fields using decades old technology.

I was hooked up to city water that, at times, when the alge mixed with the chlorine, made it undrinkable. I didn't like hauling water back from the store, but there was an old deep well out back that hadn't been used for years.

Wells clog up over several decades and a well driller suggested I first check the flow rate by pouring water into the well. This is supposed to be a good indicator of the possible flow rate out. It was only about a few quarts/ minute under a few feet of head which is probably why the pump system was removed in the first place.

No common off the shelf system will work at such a low flow rate.

I didn't need a continuous high flow rate so I used a small 1/3 hp shallow well pump to pump water out of the bottom of a water softener tank and used the resulting vacuum to bring the water up 50' in a two phase flow.

Pin holes above the water line allowed in enough air to develop slug flow. The shallow well pump only saw 25' of liquid, but it was being used as a deep well pump. A float switch in the tank cut the pump, opened a solenoid valve and restarted the cycle when the water got low.

It paid for itself in a few months and was a lot of fun. I calculated the efficiency which compared to conventional systems. I used it for four years before I moved.

Two phase flow is common in materials handling. Plastic pellets, for example, are discharged with a similar vacuum/separation tank system

The need will probably never appear in real life but you can always get a bucket of water from any depth with just 1/4" tubing for capillary slug flow and a shop vac.

Bret Cahill

What evidence do you have thatyou keep insisting that your solution is better than the one Nomad used. The fact is that the pressure spike on a long run of pipe on start-up (and quite likely on shut-down also) is not good for the system and will when the pipes get old and rusty (and they will eventually) lead to an earlier failure of the system. Chances are good, there is something about the capacity of the pump and the length of pipe to the house that creates a resonant condition that amplified the startup pressure pulse. Anyway, it's not good to just ignore the pressure spike and let it continue. And sure there is still a pressure pulse in the short length of pipe from pump to surge tank but that doesn't involve a long column of water being cracked like a whip (i.e. at a rate faster than the needle moves on the pressure gauge). And maybe it isn't of the magnitude where the water column separates and crashes back together but it still isn't good and he did well to get rid of it. After he solved the problem there is no benefit to moving the sensor and incurring the additional cost, work and maintenance that would involve.

-jim

Dear --:

Only on the suction side of the pump. Not where the pressure switch is reported to have been.

And how did this "steel rod" of water become already moving, since it has distributed inertia? Did it perhaps require

*pressure* and *time* to accelerate? The pressure spike had nothing to do with:

Acceleration of mass requires force. In the case of a fluid, this is usually a gradient in pressure, and the line pressure stays pretty close to tank pressure, even at startup. Note that the OP indicated that changing to 1.25" line did not have any effect, where with your "model" it should have had an effect.

David A. Smith

What evidence?? 80 years at least of these systems operating in the field without the dreaded fatigue and pipe failure you are referring to. There are systems out there with runs of over 1/4 mile from the pump to the tank with the switch at the tank. Again: A pressure pulse is NOT a water hammer. The pressure pulse damps out at the first opportunity - the tank before he did it, the surge tank after he installed it.

A "long water column being cracked like a whip"???. You push on one end of the colume, pressure builds on that end and propagates along the colume. Just where is this dreaded 'crack like a whip'??

As to the benefit of moving the switch after he put the surge tank in. Correct, very little except for the occasional maintenance of having to air up the surge tank. It still comes down to a band-aid approach to a non-problem if done correctly to begin with.

Harry K

Here's a more radical thought. The thread seems to have converged on a pressure pulse occuring at motor on. Why an over pressure pulse.

One way to explain it is to use the transmission line electrical analogy.

Put a voltage step onto a transmission line (like a co ax) and the pulse travels to the far end - and stops there if the end is matched to the line.

If the line is open circuit at the far end, the pulse gets to the far end and bounces back at double height. If the line is shorted at the far end, the pulse bounces back as a negative image of the incident pulse.

In this case, because the start pulse seems to come back twice as high

- assume that the far end is terminated in a high impedence. So the far end pipework narrows or the far end bladder is too stiff.

THERE's a new insight!

Brian W

Dear Brian Whatcott:

Actually it seems like it turned into a shouting match...

Only if you continue to add power in resonance.

That doesn't sound right.

Narrowing has been eliminated to no effect. Bladder is about

1/10th of a second away at the speed of sound in water. Resonance is contraindicated, since the phenomenon stops after a short time.

You are bored!

David A. Smith

Hehe....maybe - but transmission line mismatch is not a resonance effect. You can easily demonstrate the effect (even the one that doesn't sound right to you), with 50 ft of coax, a relay, a battery and of course, a scope!

Brian W

Only looks that way. Perhaps because you appear to have skipped much of the thread... The far end pipe does narrow, but changing it may no appreciable difference. The far end bladder is not too stiff, because then the pressure would only increase, not be a spike.

The pressure spike it high, not because of a bounce back, but because water is incompressible, water has mass hence inertia, and pipes have friction. The pump starts, wants to move water, water does not start to move instantly, so the pressure seen near to the pump has a high spike that rapidly reduces as the water starts to move.

Not rocket science, well understood in well pump systems for many years. That is why the proper installation puts the pressure switch near the pressure tank. (My system, for example, has 150-200ft between pump and tank, and less than 3ft between tank and pressure switch.)

sdb

I would assume the pump power comes from the house? Why not put the pressure switch in the house next to the tank and break the power there? go from the breaker panel to the pressure switch, to the pump house. Put a disconnect switch in the pump house so you can service the pump and wire from there to the pump. You can use the existing wire from the house to the pump, so it should be easy to do. The voltage drop in the existing wiring should not change, as the wire length is no different than before. You have just changed the location of the switch, so everything should work just fine.

Of corse if the power feeds the pump house from somewhere else, forget I said anything.

BTW, Every shallow well and booster pump I have ever worked on or installed, said set air precharge to 2 PSI below switch cut-in setting in the instructions. It gives you the biggest draw down on the bladder tank.

Stretch