1-1/2" or 2" pipe from well to storage tank?

[Gustave]

Hello,

This is my first post. My wife and bought 10 acres in Paso Robles CA. We are now building a house.

The property came with a well and pump. The well report says the well is 500 ft deep and produces 10 GPM. I don't know anything about the pump, but the installed pump controller is limited to 2 HP. So I assume the pump is less than that.

We have installed a 10,000 gal galvanized tank on the hill behind the house, as per Cal Fire Code. It is 80 ft higher in elevation than the top of the well. I am about to dig a trench to lay pipe from the well to the tank. I am debating between 1-1/2" or 2" PVC.

At 8-10 GPM I am not sure if the friction will really be all that different. And I'm not sure if there are other considerations.

Any advice would be appreciated. Thank you.

Gustave

 

[Osage Hills Craig]

Hello,

This is my first post. My wife and bought 10 acres in Paso Robles CA. We are now building a house.

The property came with a well and pump. The well report says the well is 500 ft deep and produces 10 GPM. I don't know anything about the pump, but the installed pump controller is limited to 2 HP. So I assume the pump is less than that.

We have installed a 10,000 gal galvanized tank on the hill behind the house, as per Cal Fire Code. It is 80 ft higher in elevation than the top of the well. I am about to dig a trench to lay pipe from the well to the tank. I am debating between 1-1/2" or 2" PVC.

At 8-10 GPM I am not sure if the friction will really be all that different. And I'm not sure if there are other considerations.

Any advice would be appreciated. Thank you.

Gustave

I'm certainly no engineer, but I've got experience pumping water up my hill. I've got 2 pump houses now (just finished the 2nd one). I know the specifics of the 2nd one the best so I'll describe it. My pump house (where the pump is) is approximately 35' below the house that it supplies. The water line from the pump house to the house is 1 1/2". The issue I faced, and I suspect you will too, is that I lose quite a bit of pressure going uphill.

I've installed a 60/80 psi switch on my pump. My pressure (bladder) tank is set at 58psi. So, my pump kicks on at 60psi and runs to 80psi. I've bought a simple water pressure tester and test the pressure at the house. Over that 35' rise, I lose 35psi. Now, the difference in yours and mine is that I need shower head pressure and you need storage tank trickle pressure. My point is you might get 10GPM at the pump, but you'll see much less at the 80' rise to your tank.

You can get an idea by running garden hoses from the pump to the tank, and measure the flow there. Of course, that's a 5/8" hose.

BTW - my other pump house is on a 2" line, but it's probably closer to 45' down the hill. I've had to run an 80/100 switch on it. The pumps deliver equivalent water to the house (I actually have 2 houses, a pump house for each; but I've got the houses connected, so I can run them both off of either pump - never both pumps). When we built the first house an engineer said the 2" would have a lot less friction (turbelence) than a 1". In my case there are no joints between either pump and the house, so it's purely wall friction.

 

[Sponsor]

 

[Reach4]

I don't know anything about the pump, but the installed pump controller is limited to 2 HP. So I assume the pump is less than that.

I assume the pump is exactly 2 HP.

At 8-10 GPM I am not sure if the friction will really be all that different. And I'm not sure if there are other considerations.

If the distance is not great, 1-1/4 would be good. 1 inch would probably be enough.

On the other hand, the pipe from the tank to the house could benefit from being bigger.

http://www.pressure-drop.com/Online-Calculator/ is not the easiest to use, but it is a good pressure drop calculator.

 

[Gustave]

I assume the pump is exactly 2 HP.


If the distance is not great, 1-1/4 would be good. 1 inch would probably be enough.

On the other hand, the pipe from the tank to the house could benefit from being bigger.

http://www.pressure-drop.com/Online-Calculator/ is not the easiest to use, but it is a good pressure drop calculator.

Ah crap, I forgot to mention the distance from well to tank is about 750 ft. The elevation gain is 80 vertical feet.

 

[Gustave]

I assume the pump is exactly 2 HP.

OK Thanks.

http://www.pressure-drop.com/Online-Calculator/ is not the easiest to use, but it is a good pressure drop calculator.

I will check that out.

 

[Osage Hills Craig]

You didn't say how long a run you had from your pump to the storage tank, but you did say you were considering PVC. With PVC, you'll have a joint every 20'. You can get polyethylene pipe in 500' or 100' rolls. Many less joints, although the C-Pak connectors (brass compression), are about $30 ea.. Much less turbulence with 2" over 1 1/2", and with fewer joints. The poly pipe is also more flexible. If you get it in, and your joints don't leak, you're good for life.

You just need enough GPM to replace your used water in a 24 hour period. I don't know what all you're trying to run off of it, or how many gallons / day you need; but with a storage tank you just need to be able to replace your 24 hour usage with what you can deliver in 24 hours. For example, my new pump house has a 305 gallon storage tank (cistern). I get my water from the city via a main, so I have a meter (I just have to get it up the hill). I used 3,600 gallons in 30 days, or 120 gallons / day (just my wife and me - retired). So, I only need to deliver roughly 120 gallons / day (the storage tank acts as my buffer). That's only 5 gallons / hour (trickle).

 

[Reach4]

Ah crap, I forgot to mention the distance from well to tank is about 750 ft. The elevation gain is 80 vertical feet.

Be aware of thermal effects. https://www.charlottepipe.com/Documents/PL_Tech_Man/ExpansionandContraction.pdf

If you run polyethylene, don't pull the pipe tight. Snake it to allow for contraction.

 

[Gustave]

I'm certainly no engineer, but I've got experience pumping water up my hill. I've got 2 pump houses now (just finished the 2nd one). I know the specifics of the 2nd one the best so I'll describe it. My pump house (where the pump is) is approximately 35' below the house that it supplies. The water line from the pump house to the house is 1 1/2". The issue I faced, and I suspect you will too, is that I lose quite a bit of pressure going uphill.

I actually have a PhD in Fluid Dynamics! But all of that is pretty rusty.

I do know that for every foot of elevation you gain 0.43 psi of pressure. Thus from my storage tank down to the house (which is 80 ft lower) I gain about 35psi depending on the level in the tank (it's quite tall).

But, as you mention, the issue of filling the tank is a little different. I am more interested in flow rate than pressure, though the two are related. I am looking for folks with experience in this area for some kind of guidance. Rule of thumb type of thing.

Thanks for the input.

 

[wwhitney]

Hazen Williams formula:

https://en.wikipedia.org/wiki/Hazen–Williams_equation

If you move 10 gpm (probably more than you need, as other noted) 750 ft through a pipe with a 2" ID and a roughness factor of 150, then the frictional pressure loss is only 0.77 psi. With 1-1/2" ID it's only 3.1 psi. For greater accuracy, you'll need the exact ID and the roughness coefficient from the manufacturer.

Seems like to first order you can just design for the pressure loss due to altitude.

Cheers, Wayne

 

[Gustave]

Hazen Williams formula:

https://en.wikipedia.org/wiki/Hazen–Williams_equation

If you move 10 gpm (probably more than you need, as other noted) 750 ft through a pipe with a 2" ID and a roughness factor of 150, then the frictional pressure loss is only 0.77 psi. With 1-1/2" ID it's only 3.1 psi. For greater accuracy, you'll need the exact ID and the roughness coefficient from the manufacturer.

Seems like to first order you can just design for the pressure loss due to altitude.

Cheers, Wayne

Thank you. I am curious how the friction affects volumetric throughput. Will 10 GPM at the top of the well translate to say, 8 GPM at the tank?

My wife and I do not use much water. Maybe 50-60 gallons per day on average including some drought tolerant landscaping. that's here in town in a suburban development. But it will be more out on the 10 acre lot. Especially when we have guests.

 

[VAWellDriller]

Thank you. I am curious how the friction affects volumetric throughput. Will 10 GPM at the top of the well translate to say, 8 GPM at the tank?

My wife and I do not use much water. Maybe 50-60 gallons per day on average including some drought tolerant landscaping. that's here in town in a suburban development. But it will be more out on the 10 acre lot. Especially when we have guests.

Can't be answered without knowing the well drawdown and pump model.

 

[wwhitney]

Thank you. I am curious how the friction affects volumetric throughput. Will 10 GPM at the top of the well translate to say, 8 GPM at the tank?

Unless your pipe leaks, 10 gpm going in is 10 gpm coming out. The question is simply how much pressure the pump at the well has to overcome to get 10 gpm to come out at the tank. And that's the pressure due to the height of the water column, plus the frictional pressure loss.

Cheers, Wayne

 

[Gustave]

Can't be answered without knowing the well drawdown and pump model.

Here is the report that I am fairly sure is the correct one. May be helpful though still does not say what pump model is down there.

The difference in price is not that much so I will probably go with 2" on the way up to the storage tank and from the tank to the house.

Thanks to everyone for your input.

 

[Gustave]

In case anyone loves topo maps (I do)...

 

[Valveman]

Assuming it is a 10 GPM series 2HP pump, from 407' it will deliver 10 GPM at 70 PSI and 9 GPM at 90 PSI. So basically 20 PSI friction loss would also decrease the pump output by 1 GPM. I would stay with pipe large enough to keep friction loss below 20 PSI at 10 GPM flow.

You can get poly in 500' rolls. Dresser couplings are not forever connections. I have a long poly line with dressers that I am having to dig up one at at time and butt fusion weld the pipe together. The roots got into the dresser, made there way into the o-ring, and compressed the area so much they turned round o-rings perfectly square, and make them leak. Poly also expands or contracts an inch for every 100' for every 10 degrees in temperature. My 3500' pipe lines gets 11' longer or shorter depending on the time of year and the ground temperature.

A rise of 35' should only be 15 PSI loss. A rise of 80' is 35 PSI loss.

 

[Gustave]

Assuming it is 1 10 GPM series 2HP pump, from 407' it will deliver 10 GPM at 70 PSI and 9 GPM at 90 PSI. So basically 20 PSI friction loss would also decrease the pump output by 1 GPM. I would stay with pipe large enough to keep friction loss below 20 PSI at 10 GPM flow.

You can get poly in 500' rolls. Dresser couplings are not forever connections. I have a long poly line with dressers that I am having to dig up one at at time and butt fusion weld the pipe together. The roots got into the dresser, made there way into the o-ring, and compressed the area so much they turned round o-rings perfectly square, and make them leak. Poly also expands or contracts an inch for every 100' for every 10 degrees in temperature. My 3500' pipe lines gets 11' longer or shorter depending on the time of year and the ground temperature.

A rise of 35' should only be 15 PSI loss. A rise of 80' is 35 PSI loss.

Thank you for that.

Gustave

 

[wwhitney]

Poly also expands or contracts an inch for every 100' for every 10 degrees in temperature. My 3500' pipe lines gets 11' longer or shorter depending on the time of year and the ground temperature.

I'm curious--does the pipe actually get longer, i.e. the pipe is relatively loose within the soil, and there are places you've allowed for the extra length to accumulate? Or is the pipe effectively constrained by friction with the soil, so the actual length remains unchanged, and the pipe just undergoes some distributed stress to keep its length different from what it would be if unconstrained?

Cheers, Wayne

 

[Valveman]

I left some slack and did as many s turns as possible, but it wasn't enough. Yes the pipe gets 11' longer in the summer and 11' shorter in the winter. Had to make some big bends before terminating into a threaded fitting or it would break the threads. Also had to concrete thrust block those ends to hold them in place. Ever wonder why big electric high wires have a zig zag every so often? Or wonder why they have those big Z patterns in the Alaska pipeline. I think they call it "Sun Kink". but it happens to hiways, electric lines, pipe lines, and everything.

Just adding some more here, I am also having a problem with this pipe trying to climb out of the ditch. When it expands it lifts up in the ditch. Then the rain settles and packs dirt underneath the pipe. So when it contracts it crawls up out of the ditch. Took several years but where I didn't leave enough slack the pipe is getting more shallow.

I should also add that this pipe is also coming off a water to air heat pump. So where normal pipe might see 20 degree change from high to low I can see as much as 70 degree difference from 40 to 110 degree depending on AC or heater running. Regular water lines shouldn't expand and contract nearly as much.