I just had a new pump installed. The old 1 1/2 HP Red Jacket finally burned out after 18 years. Replaced it with a 1 1/2 HP Stainless Steel Franklin Electric.
Well is 400' deep, pump sits at 360ish and static water is 250ish.
I watched them pull the old one out and I noticed the 1" PVC that is in there is rated I believe for 125 psi.
If that's the case and I put in a CSV, wouldn't the back pressure exceed that rating when I'm running say a sink or flushing the toilet? The last thing I want is a burst line 300' down. I'm already out $2,000 for the new pump and labor.
Is my concern valid when using a CSV?
Thanks for any info.
This can’t be right. I guess it is possible that your pump man screwed up and used 125 PSI pipe in that well, but I doubt it. Assuming you have a 10 GPM series, 1.5 HP pump the pressure from just being set at 360’ is the same as 155 PSI, then add the 60 PSI that the pump will build before the pressure switch shuts it off and you have a total of 215 PSI on the bottom joint of pipe. That is 215 PSI with the old style pressure tank only system, so the pipe needs to be rated for more than that.
Now adding a CSV will put more pressure on that pipe. But the 10 GPM series pump can only build 251 PSI total, even against a closed valve. So there is only 36 PSI more pressure on the pipe when using a CSV than when not using a CSV.
I think what you saw was 1” SCH 120 on the pipe. That is much more common for drop pipe, and is what your well needs because of the depth. SCH 120 pipe has a rating of 360 PSI. On top of that the burst pressure of any plastic pipe is usually 2 to 5 times the working pressure rating of the pipe.
Pressure rating of the pipe is important when using a CSV, but isn’t as much of a problem as you would think. Drop pipe has never been an issue with a CSV because as stated above, it has to be strong enough to handle the depth and pressure of the pump anyway. The CSV doesn’t usually add much pressure to the drop pipe.
The pipe from the wellhead to the CSV is usually more of a concern than the drop pipe. But you can subtract the static water level from the total pressure the pump can build, because it has to lift this much to get water to the surface, so you don’t see that much pressure on the underground pipe. In your case, if I am right about the 10 GPM series pump, your underground pipe before the CSV will see up to 142 PSI. Even SCH 40 PVC or 160# poly is rated for more than this, so you should not have a problem.
You are smart to ask this question as it is one of the only concerns when using a CSV on such a deep set pump. But once you see that your pipe is rated high enough to handle the pressure, you should realize the extra backpressure from the CSV is good for the pump. The extra backpressure from the CSV is what keeps the pump from cycling itself to death. The CSV puts just enough backpressure on the pump to make it pump exactly the amount of water you are using, so the pump is not cycling on and off while you are using water at any flow rate. And that is the best thing for the pump.
Also the CSV eliminates water hammer from the pump starting and stopping. Water hammer happens in a fraction of a second, but can be 10 times the pressure that the pump can build. A water hammer “thump” when the pump starts or stops with the old conventional tank only system can cause a pulse of 2500 PSI on your pipe. So not only is the backpressure from a CSV a good thing for the pump, but it is also good for the pipe. The CSV makes the pipe see a max pressure of 251 PSI with that 10 GPM pump, but that is much better for the pipe than water hammer pulses of 2500 PSI from an old conventional pressure tank system cycling on and off.
To sum it all up, if that is 125 PSI pipe in the well you will have problems even without a CSV. But if it is Schedule 120 as it should be, then backpressure from a CSV is not the problem, it is the solution.
