100 PSI vs 160 PSI Black Poly Pipe

The weight of the water column in the pipe. The deeper you go the more pressure that will be felt at the pump due to the weight of the water in the pipe.

Not sure I understand your reply as to impact or risk associated. I get that the pressure will be felt at the pump due to the weight of the water in the pipe but what's the risk? Will the pipe burst? Or just expand a little more than 160 PSI so water pressure will be reduced for normal flow?

I doubt at 125 feet you will have any problems. The 100 psi is working pressure. There is a safety factor worked in to all pipe. Pressure at 125 ft of water is about 56 psi.

I agree. Don't fix it if it ain't broke.

I also agree that the 100psi pipe will be ok - but note that in the OP, Bill states "My well is 220';" - hence my calculation of the pressure at just under the pipe rating.

125' is mentioned in another context.

At 220' you'll have just under 100psig.

It'd be just over 130psig at 300', so (just regarding the pressure) it looks like you'd get away with it, while your neighbours are living on the edge.

I guess if it did fail, it wouldn't do any direct damage.

I don't know what other factors (if any) come into well pipe selection.

Wouldn't the pressure in the tank be added to water column pressure?

The total head (cause of the pressure at the bottom) woud be from the highest point to which water is pumped (top of header tank if entry is below water level, or inlet to tank if above water level) to the surface of the water in the well.

Agreed that is the head pressure. We are though pressurizing the tank most systems 40 to 60 psi. This pressure wouldn't it be added to the water column pressure as felt at the pump?

Re: We are though pressurizing the tank most systems 40 to 60 psi. This pressure wouldn't it be added to the water column pressure as felt at the pump?

Yes, that 40 to 60 psi would be added to the water column pressure as felt at the pump, unless you have some strange (to me) design as I mention in my post #6 (which is in response to post #4).

Yes, I would expect so, unless something special is done. I don't have a well--you could use a deepwell pump to pump the water from the well to a non-pressurized sort of holding tank, then have a 2nd pump to pump the water from there into a pressurized tank / system. I don't expect that's the normal approach.

Each foot of head equals .433 PSI. Then add the pressure exerted by the pump to move the water cloumn upward.

Thanks to all for the quick replies.

Other factors in all this is that our well hit a natural vein so flow was 22 GPM without a pump even being installed and the water rose from the well base to within about 20' of the top of the well or "drawdown" water level. While the drill was still in the thing sprayed under pressure. So the pump is therefore only pushing the water about 22' straight up and at the well head connection it flows to the crawlspace under the house (about 100') but this is all downhill from where the well is to where the bladder tank is under the house. I'd estimate the drop is at least 10' in that 100' of pipe to the bladder tank under the house. When on my front porch or 1st floor in the house and I look at the neighbors house I'm looking into his second floor windows and his house is only 60' from mine side to side. Yes, our house is on the highest point of the road - if you drive down the street to the creek it's 1 1/2 miles and the road drops about 90' in that 1 1/2 miles. Relatively speaking the drop in my crawlspace is code minimum or 32" to about 5' on the end with the water heater and bladder tank; foundation width is 36'.

Something else I've learned this morning is my neighbor said my pump was the cleanest pump of any of our four family neighbors when replaced. He said his was covered in mud from probably being placed to close to the bottom of the well. My well depth is technically 240' but the old pump was at 220' or 20' above well bottom. Replacing it this time to reuse the power cord we probably nipped 5' off the power cord to splice and reuse both at the pump and at the power box at the top of the well. True pump depth is most likely approximately 215' deep.

The more I learn the more lucky I am. Our pump being higher than average above the well bottom most likely kept it out of the mud, dirt, rock that it last 17 years while my neighbors pump went at 12 years and ditto for the other neighbors. The deeper the well and the lesser the natural flow or GPM the quicker the pump wears out...

Ah! The bigger picture!

As I mentioned, the maximum pressure^[1] depends only on the difference in height between the (minimum anticipated) water level in the well and the highest point to which the outlet has to pump (including any head in the storage tank). In your case, the pressure would get no-where near 100psi.

Here's a slight caveat here, because if the pipe were initially empty (even though the outlet is lower than the well-head), the pressure on the pipe walls would rise according to the difference in height between the well level and the highest point of the pipe. Once the pipe is full, syphoning would reduce the pressure.

If I've got the picture right, that would mean your pressure (at the pump outlet) rising to about 10psig when pumping up to the 22' level, then dropping back to about 5psig when the pipe is full (head = (22' rise - 10' drop) = 12').

[1] By which I mean the differential pressure to which the pipe walls are subjected.

Addendum:

If your tank is pressurized, the tank pressure must be added to my figures.

Credits to ozzb (at #4) and rhkramer (at #14).

Good morning,

The OP said his bladder (tank) was under the house, so I would think it'd have to have a checkvalve and be pressurized. If it held the pressure at say 80 psi, then the total pressure at the pump depth would be 175 psi (80 + 95).

The pressure required to overcome the vertical height would be 95 psi (220' * 0.433psi/').

The pump is 220' below ground level (in a 240' bore-hole), but the important figure (regarding the pressure) is the water level in the well - stated in #12 as 22' below ground level.

"at the well head connection it flows to the crawlspace under the house (about 100') but this is all downhill from where the well is to where the bladder tank is under the house. I'd estimate the drop is at least 10' in that 100' of pipe to the bladder tank under the house."

Looks like about 12 feet of head + tank pressure to me, too.

This is such a pleasure after trying to deal with the cavitation/pure gas/oil overflow nonsense of that other thread.

The bladder tank is a 20 gallon unit pre-charged at 40 PSI. I replaced it with the water heater last year both of the previous units lasted 16 years so I purchased the same units. Water heater State 40 gallon low boy electric. Amtrol 20 gallon bladder tank.

Remember the original question was as to the risk if any of using 100 PSI versus 160 PSI black pipe. From all the posts I am assuming a couple things.

Worst case is the black pipe can or could burst if the pressure is greater than it can tolerate. I just heard yesterday from a co-worker they changed their pump and piping (PVC 200PSI) only to find out the pipes had cracks and were leaking.

Aren't bladder tanks capture systems and the pressure only goes one way like the water into the house piping system not back down through the PVC to the well head?

"Aren't bladder tanks capture systems and the pressure only goes one way like the water into the house piping system not back down through the PVC to the well head?"

Trouble is you have to overcome the bladder tank pressure when water's going into it (otherwise it just plain wouldn't go in - check valve or not) - so the bladder pressure must be added to the pressure due to the water head to get the worst-case pipe pressure.

"I just heard yesterday from a co-worker they changed their pump and piping (PVC 200PSI) only to find out the pipes had cracks and were leaking"

Was it the old pipework that was ripped out that had cracked, or the new stuff? If the old pipes, could be that ageing plus vibration (from the pump) had taken their toll. Also how long was the old pipework in there? How high were they pumping (relative to the water level in the well-bore)?

I meant "captive" system which it is per the manufacturer.

The other folks tried using their old PVC pipe. It usually cracks and breaks when pulled manually using hand over hand muscle power of 2 folks.

But, atmospheric pressure, acting on the sufrace of the well water cancels out all the head requirements, except for those required to push the water above the surface of the well water. All things taken into account and discounting friction losses, we have 12 feet of head + 40 PSI tank pressure = 45PSI.

What I've learned.

Original question: "Am I at risk for using 100 PSI black pipe versus 160 PSI black pipe when replacing my pump."

Answer: No

Pressure generated equals number of feet of static water level (distance of well head to well water reservoir) x .433 + pressure created by bladder holding tank 40. 22 x .433 + 40 = 49.56 PSI

When pump cycles on the static water level drops or "drawdown" then well plateaus with natural recovery flow. It will remain down until well recharge rate is factored in but it also depends on how much water is being used. Toilet flush 1.5 gallon no real drawdown; i.e. showers/baths/car washing/lawn watering big users.

House flow rates (1/2" pipe in perfect world would allow 23 gpm with no joints, bends or restrictions. Restrictions include other factors (low flush toilets, shower head 2 gpm restrictors, kitchen faucet nozzles, etc). Measured rates: kitchen sink flow rate 3 gpm, master bath shower flow rate 3 gpm (downstairs), master bath jacuzzi 3'x6' 10 jet requires 60** gallons minimum 6 gpm, upstairs (pressure lowers) shower 2 gpm, bath 3 gpm.

Without actual measuring drawdown for variables at least five days I am falling back on a USGS-NC Water Report 2008. As 2008 was an "extremely severe drought" which studied 650+ private wells so data is available and substitute with judgment.

Average drawdown *75'; 75 x .433 + 40 = 72.47 PSI (*absolute worst case scenario as 2008 extreme severe drought was USGS report base for average drawdown)

Note: *Average drawdown is based upon continuous water flow till well natural flow plateaus (recharge rate) within the well case pipe during 8 hour period. My water table recharge rate is 475 gallons per 8 hours or 59.35 gallons per hour or .98 gpm (happen to live in the highest recharge rate district out of 12 districts county section for USGS report - or 3 miles from Falls Lake; Raleigh region Army Corp reservoir which is situated directly over main ground water reservoir for 1 million population base).

Therefore if 1.6 gal of water is in 6" pipe to reach average drawdown I must use 120 gallons. **only time I come close to using 120 gallons is filling the jacuzzi with 60 gallons therefore my drawdown when filling the jacuzzi is 35' with static level recovery being 35 minutes (.98 gpm recovery above paragraph) PSI 55.15 at this point which will represent my individual average worst case scenario for a single point in time otherwise I would have to fill the jacuzzi, run the wash, open all faucets, and flush all toilets at the same time!

Other stats of interest from USGS 2008 Water Report:

Average Yield 17.6 GPM Mine 22 GPM

Average Depth 208' Mine 240'

Average Static Water Level 26.6' Mine 22'

Average Drawdown 75' Mine (see above data)

Average water temperature 59F

Thanks for the feedback / update!

You deserve an atta-boy.

Cheers.