Please critique my pump/pipe plans

[DStyduhar]

Ok, it's becoming clearer. Maybe

For my situation, maybe I should think about TDH in terms of two legs. Leg A is between well and house and then leg B will be between house and garage. I can calculate leg A head based on HOUSE GPM needs and then I can figure what gpm/psi I will have available to the garage due to additional pipe loss. If not enough to satisfy garage needs, then step up to next pump hp.....like 3/4 to 1hp assuming wiring can handle it. Or maybe increase pump gpm....7 to 10 for instance. Does this make any sense? Is there a big downside to oversizing the pump slightly?

Regarding TDH calculation (Total Dynamic Head (TDH) = Pumping lift + elevation change + operating pressure + friction loss), I'm hung up exactly on what they mean by Pumping Lift? If the pump is 100 feet down, do you just put 100? Or is this the pumping level? If pumping level, I only have that value for the max gpm of the well.

thanks,

Drew

 

[Reach4]

If not enough to satisfy garage needs, then step up to next pump hp.....like 3/4 to 1hp assuming wiring can handle it. Or maybe increase pump gpm....7 to 10 for instance.

You would first select the GPM needed, and then select the power needed to bring that water up and to the pressure tank with that GPM pump.

Regarding TDH calculation (Total Dynamic Head (TDH) = Pumping lift + elevation change + operating pressure + friction loss), I'm hung up exactly on what they mean by Pumping Lift? If the pump is 100 feet down, do you just put 100? Or is this the pumping level? If pumping level, I only have that value for the max gpm of the well.

Pumping level is the surface of the water. If the water surface pumps down, then the pumping level drops, and that would drop the flow from the pump some. There is a bit of friction loss between the pump and the surface of the water, you know that for that short distance, the friction loss is pretty negligible.

 

[Sponsor]

 

[Boycedrilling]

I spent about an hour this morning doing TDH calculations as part of an online continueing education class for my Pump installers and Drillers licenses.

I have done TDH calculations for subdivisions, calculating psi at every connection. You can do calculation to figure psi under flow at every fixture if you are so inclined. However usually we just do the calculations to delivery water to the residence or point of use.

First you have to have a desired flow rate to base your calculations off of.

The first step is then to determine the vertical depth to water in the well at your desired pumping rate. This is not the same as the static water level. Then you add to this the vertical height from the well to your point of use. This gives you total vertical lift. This figure does not change. Worst case scenario, I use Pump setting depth, if the well were to draw down all the way to the Pump intake.

The second step is to calculate the friction loss in your piping system from the pump to your point of use. This is total pipe in the well, plus pipe from the well to the house, plus pipe to the pressure tank. Then you calculate Equivilant feet of pipe in all the fittings and valves in your system. That check valve? It’s equivalent to 12-20 feet of pipe, and so on. Many tines the fittings will add another 10% or so to your pipe length. Once you have a total pipe amount, you determine the friction loss from the piping at your desired flow rate. This number changes with different flow rates. You are also looking at the velocity of the water in the pipe. You want to keep it under 5 feet per second to minimize water hammer.

The third step is to determine your desired Psi at the point of use. Multiply that psi by 2.31 to get feet of head.

Add all these numbers together to get your TDH. THEN go to the Pump curves to determine the horsepower needed to give you your desired flow rate.

 

[DStyduhar]

Ok, went through some calculations, messed around for a bit and came up with the following. I know you said to start by selecting desired GPM but I sort of worked backwards with 3/4 and 1HP pumps @ 7GPM and 10GPM. Maybe it's retarded but it made logical sense to me at the time.

1) I calculated all the friction losses and head for 7gpm and 10gpm from well to house for 50psi and 1" Poly.

7 GPM Head - Well to house - 185'
10 GPM Head - Well to house - 191'

2) Looked at the pump charts for those Grundfos 7gpm and 10gpm pumps @ 50psi and found how many GPM I would get at the house for all four pumps. Had to do a little bit of guessing/interpolation. This might be a case where the curve would be useful than the chart. What's up with the 10GPM 3/4 HP GPM?

7GPM 3/4HP - GPM @ House - ~6.7 GPM
7GPM 1HP - GPM @ House - ~8.0 GPM
10GPM 3/4HP - GPM @ House - ~5.4 GPM ???????
10GPM 1HP - GPM @ House - ~9.4 GPM

3) I calculated the pressure loss for additional piping to the shop for 7gpm and 10gpm.

7 GPM - House to Shop pressure drop - 4.36 psi drop (22') = ~45psi @ shop
10 GPM - House to Shop pressure drop - 8.2 psi drop (39') = ~42 psi @ shop

4) Looked at pump charts for new pressures above and shop head = well-to-house head + house-to-shop head. Again, had to interpolate a bit.

7GPM 3/4HP - GPM @ Shop - ~6.6 GPM
7GPM 1HP - GPM @ Shop - ~8.0 GPM
10GPM 3/4HP - GPM @ Shop - ~4.7 GPM
10GPM 1HP - GPM @ Shop - ~9.2 GPM

Is this math and my approach here even remotely correct? haha. I didn't calculate any losses for the plumbing to fixtures in the house. I can see how this is a deep rabbit hole so I gotta draw the line somewhere

thanks,

Drew

 

[DStyduhar]

Posted above right after BoyceDrilling (thanks for info BTW).

"""The first step is then to determine the vertical depth to water in the well at your desired pumping rate. This is not the same as the static water level. Then you add to this the vertical height from the well to your point of use. This gives you total vertical lift. This figure does not change. Worst case scenario, I use Pump setting depth, if the well were to draw down all the way to the Pump intake."""

His comment above is exactly what I was "trying" to ask earlier. Isn't this what pump guys refer to as the pumping level? The thing is, you don't usually know your pumping level unless you check it with an actual pump, right? So for instance, most residential wells get pumping level value @ max yield (mine is 125' for 25gpm yield). How do I know what the pumping level is for a smaller pump without actually checking it? Damn, my head hurts.

Drew

 

[Boycedrilling]

Yes, until a pump is actually installed in a well, it’s a guess what the pumping level will be.

When the driller is finished drilling he makes an estimate of how much water the well will produce. If I’m using a cable tool drill rig, I bail the well. I know my 4 1/2” bailer holds 10 gallons of water. If I can cycle the bailer in and out every 60 seconds, I’m bailing 10 gpm. I’ll bail for an hour. I can monitor the water level by marks on my sandline running the bailer. That’s a bailer test.

If I’m drilling with a rotary rig, I’m blowing the water out of the well with an air compressor. I can measure how long it takes to fill a five gallon bucket to calculate gpm. I can also place a wier in a ditch to measure larger flows. This is called airlift pumping. Unfortunately there is no way to determine how far the water level draws down during airlift pumping. On higher capacity, deep wells we get some ideas by the air pressure changes as we airlift.

Now on a domestic well, if I can airlift 50-100 gpm, it’s not going to drawdown much with a 10 gpm Pump. If I can only airlift 5 gpm, we don’t have much room for error.

On any wells that serve more than 2 homes, or involve a water right, we are required to do a 4 hour minimum actual pump test. Depending upon depths and flow rates, this will cost $1,000 to $20,000 to install a temporary pump and perform the testing. Some lending institutions will not loan money on a property without a Pump test either.

 

[Reach4]

1) I calculated all the friction losses and head for 7gpm and 10gpm from well to house for 50psi and 1" Poly.

7 GPM Head - Well to house - 185'
10 GPM Head - Well to house - 191'

2) Looked at the pump charts for those Grundfos 7gpm and 10gpm pumps @ 50psi and found how many GPM I would get at the house for all four pumps. Had to do a little bit of guessing/interpolation. This might be a case where the curve would be useful than the chart. What's up with the 10GPM 3/4 HP GPM?

7GPM 3/4HP - GPM @ House - ~6.7 GPM
7GPM 1HP - GPM @ House - ~8.0 GPM
10GPM 3/4HP - GPM @ House - ~5.4 GPM ???????
10GPM 1HP - GPM @ House - ~9.4 GPM

I think you are counting your 50 PSI twice. If you are going to include the 50 psi in the head calculation, then you would not use the 50 psi row in the tables. You would use only the 0 PSI row.

If using the tables, I would compute your effective head at zero PSI. Then you can use the various rows.

So to reiterate, I think you counted the 50 PSI twice. What do you think?

One more thing: in a 40/60 system, I think you can use 40 psi in your calculations. That is to say that if the pump can keep 40 while you are doing your highest demands, that is quite sufficient. More controversially, if the pressure stayed above 30 during those times, you might never notice. Nothing drastic is going to happen. It's not like breaking the sound barrier.

 

[Valveman]

If the pumping level is 125' while using 25 GPM, it will be 125' or higher when using less than 10 GPM. So you have 125' of lift n the well. 10 PSI friction loss after the pressure tank would mean setting the pressure switch to 50/70 to make up for that. 50/70 pressure switch means 60 PSI average with the old pressure tank only system or 60 PSI constant with a CSV, which is the same as 138' of head. 138' plus 125' is a TDH of 263'. At 263' a 3/4HP, 10 GPM pump will do 9 GPM, while a 1HP will do 12 GPM.

 

[Valveman]

I know you are hearing from people who tell you back pressure is bad for a pump and small tanks make the pump cycle for every toilet flush, but they don't know what they are talking about. Back pressure is good for a pump. It stops the cycling, and makes the pump/motor draw lower amps and run cooler. Here is a link to a few hundred people who have CSV's and know how they work. I sent you a private message.
https://cyclestopvalves.com/pages/reviews

 

[DStyduhar]

Reach - I didn't think about that but I do think you are right about counting it twice. hmmm. I will rerun the #'s and post things up later tonight.

What about BoyceDrilling's comment regarding the pumping level? Keep in mind I still don't know how deep my pump is hanging but I am assuming it's total well depth (175') +25 feet. Seems like in order to figure the TDH you need pumping level. To get pumping level you need to pump down the well with the gpm pump that you plan to use? I can't imagine pump guys are putting in test pumps and then determining the pumping level to calculate the TDH, that seems so overkill.

How do you work around the pumping level #'s in TDH? Like Valveman said, I know the pumping level will be greater than 125', since that is the pumping level @ max yield (25gpm).

thanks,

Drew

 

[DStyduhar]

Valveman, appreciate the comment/info. In what cases would you recommend a larger pressure tank with a csv? What is the downside of using something larger? Wouldn't that further help reduce # of pump cycles for small usage things like washing hands? I'm still learning about the csv but from what I have read, it only really works if demand >1gpm, correct? Just thinking out loud here. I am already set on buying a csv but trying to get all the angles

 

[DStyduhar]

OK dudes, went through the #'s again using worst case 125' as my elevation head (previously used 50). Also, as per Reach's suggestion, I did not add 50 to the TDH calculation as I was double dipping. Like previous calculations, 3/4 7GPM pump doesn't look to be a good fit here. Again, I have only been looking at Grundfos charts.

 

[Valveman]

It would be nice to know if the pumping level was 125' at 25 GPM. But your pump is set at 175', so 175' is your worst case scenario. I would use the 10 GPM, 1HP pump. At 125' pumping level it will give you12 GPM, but if the water level pulls down to 175', it will still pump 10 GPM at 50 PSI. In the past you didn't want to oversize a pump as that would cause it to cycle more. But with a CSV you can install as large a pump as you want, and the CSV will make it work like a smaller pump when small amounts of water are being used.

With a CSV the 4.5 gallon tank is all you need for 40/60 pressure or less, 1HP or less, and with a one family house. I would switch to the 10 gallon size tank for 1.5HP or larger, pressure settings 50/70 or higher, and/or multiple houses or more than a one family house. Sure a larger tank with a CSV will cause fewer cycles, but not enough to justify a larger tank. Even an 80 gallon tank only holds 20 gallons of water. Your water does not come from the pressure tank, but rather from the pump and well. You have millions of gallons of water stored in the well, 20 gallons extra in a pressure tank isn't doing any good. The only thing a pressure tank is for is to reduce the cycling, and when you have a CSV doing that for you, a larger pressure tank is not needed. When using water with a CSV system, the water is just going right past the tank straight to the faucets. It doesn't matter if it is a 1 gallon or a million gallon tank. Really the only time the tank is being used is when you are using water for little intermittent uses, and then the pump is only cycling intermittently, which isn't going to hurt a thing.

 

[Reach4]

I have not checked the "well to house numbers". I don't even understand what the "shop to house" numbers are intended to represent. That's OK. I don't need to. I think in your calculations, you are presuming that the shop is consuming the whole water flow.

If you find the pipe pressure drops to be too high, you can up the pipe size. The house to shop pipe could be bigger than the pipe from the well to the house. And the pipe from the well to the house could be bigger than the drop pipe.

If you look at S.I.D.R. PRESSURE PIPE ASTM D2239 table on page 6 (of 8) of http://www.jmeagle.com/sites/default/files/jme_PEWaterandSewer.pdf , you can see the ID of the different sizes. With SIDR (ASTM D2239) the ID is the same for different pressure ratings. That way the same barb is used for different pressure ratings.

 

[DStyduhar]

Valveman - I was told the pumping level was @ max yield. I don't know how deep my pump is set....the well depth is 175'. I am going to have a local pump guy come out and do a recovery test on our well and also pumping level for 10GPM.

Reach - Sorry for the confusion, dude. "well-to-house" was just to try and determine how many psi and gpm available @ the house. House-to-shop was run to see how much pressure loss and get an idea of how much mojo I'll have to the shop.

 

[DStyduhar]

Also just noticed that the 10GPm pumps have 1.25" outlet, 7GPM have 1". I measured and know for a fact that I have 1" poly. Do folks ever use 1.25" NPT to 1" barb? What's the effect of doing this on pump?

 

[Valveman]

Just take whatever size the pump is made for and bush it to fit the pipe.

 

[DStyduhar]

Stopped by the local well place today and the owner said the majority of what they sell are Frankjlin J Class and he has only had two returns and most are in the ground for 15-25 years. He felt Grundfos would be a waste of money for what I am doing. I wasn't sure if Grundfos used Franklin motors....? I also brought up the stainless impeller thing and he said the new material that Franklin uses (some Teflon based thing?) is really strong.

Quote me a Franklin J Class 1HP/10GPM for $570 out the door.

thoughts?

Drew

 

[Valveman]

If I remember right Franklin bought Jacuzzi in 2004 and went into the pump business. I believe they have even changed the Jacuzzi design completely since then. That math doesn't add up. I like their motors, which btw will fit Grundfos or most any other pump. But I am not impressed with their pumps. I am not sure it it Teflon, but something slick like Delrin. They have to be slick with a floating stage design as two pieces of plastic rub each other. That doesn't happen with floating stack designs like Grundfos, as the motor thrust bearing holds up the stack so nothing touches.

 

[DStyduhar]

Had some local well guys come out and we opened everything up (even the hose bib on top of well head) and pumped it down for 20 or so min using the current pump that was installed. The pump is prob a 1HP, 10GPM.

- Static was 50ft (same as I measured last time)

- Pull down to 72ft

- Was recovering 10ft in 5 min, he said the math works out to about 3GPM recovery. Told me the recovery is generally better deeper in the well

I ran the numbers on recovery and I'm getting 2GPM, not 3GPM. Can someone confirm what I'm doing wrong?

if recovery is 10ft in 5 min....then 2ft in 1min. 2ft = 24"

Calculate volume for 6" casing= (24") x (piD) = (24") x (18.84") = 452 cubic inches.

Found a calculator online to convert volume to gallon and it shows 452 cubic in = ~1.95 Gallons.

Please advise.

thanks,

Drew