Looking for help with some design questions for submersible pump

[Reach4]

But this doesn't actually account for the friction losses in the fittings. I feel like when I work with this I get a range of values and would love a source you think is good for calculating this. Without the CSV and the pressure tank/switch in a valve box deal at the wellhead, my fittings look something like this for each cistern: long barb, long barb, pitless adapter, barb, ball valve, T that water flows through for PT, ball valve, T that splits the water, ell, ell, pass through for the cistern.

https://www.pressure-drop.com/Online-Calculator/ pressure drop calculator is more complex than what is usually called for.

Note Gruppe (group-- plumbing element) Untergruppe (the shape)
Calculate for each piece, and add the drops.

 

[chickenranch]

Ok now to the problem you haven't seen yet. With both cisterns open to 12 GPM, the system pressure will fall to zero when both are filling at the same time. Unless you use a Dole valve or something to restrict the pump, it will be splitting 15+ GPM into both cisterns, and the pump will be in upthrust. Not only that but when you go below the air charge pressure of a diaphragm tank of any size it makes water hammer. Then when the cisterns are full and the both valves close, the system will water hammer again as the pressure hits the air charge in the tank. This water hammer is usually strong enough to bounce the pressure switch on/off rapidly. ESPECIALLY with a small tank. Did I mention the damage to the check valve that happens every time it slams shut form 12-15 GPM?

Meant to get back to this part a few days ago but it dropped off the radar.
Established I won't be at 15gpm, more like 12gpm, but I hadn't thought about the pressure tank and bladder part and you're right, I would be well below even 18psi. Why does this alone make for water hammer? I see that if a valve closes rapidly then the bladder isn't going to do anything to help soften that blow. Makes sense. It also kind of seems like the bladder wouldn't like being at a higher pressure than the water? But maybe not.

Looking at the motorized ball valves they have a 5 second closing time. Would this be enough to ramp things down slowly enough to prevent water hammer and slamming the check valve shut?

Anyway these are important issues I would not have thought of on my own, thanks! I do think I'll need to look at maybe the 15SQ or a 10SQ with more stages, though, to get the flow I want for both cisterns with the CSV set at say 30psi for a 20/40 switch since I do have the additional head for getting to the cisterns. If there was just one cistern at the well head I could probably get away with the current pump.

 

[Sponsor]

 

[chickenranch]

As to which CSV to use, CSV1A or CSV125, it will make little difference in this case. The CSV1A will be best because it is adjustable and you need it set for 30 PSI. The only time it will be at less than 6 GPM is for the minute it is filling the pressure tank before shut off. The CSV will work no matter where you put the pressure tank, but the CSV needs to be on the well line before it tees off to the other cistern.

Yes I like the adjustable nature, and of course it has a much bigger range, too.

Makes sense the CSV would need to be placed before the tee. I guess I wonder if having the tank and switch would cause any problems for the CSV or if would still buffer water hammer reasonably well.

Can you give a clearer answer on how to read the tables for the CSV1A on your website? The reason I ask is not because of this well to cistern system where the flows are fairly low and the pressure is not super important, but for the pressure system that is downstream of the cistern serving house and garden. Since that will have higher flow requirements (15-20gpm) and pressure standards, it makes a big difference is the friction loss and pressure falloff are COMBINED compared to only one being relevant.

 

[Valveman]

Meant to get back to this part a few days ago but it dropped off the radar.
Established I won't be at 15gpm, more like 12gpm, but I hadn't thought about the pressure tank and bladder part and you're right, I would be well below even 18psi. Why does this alone make for water hammer? I see that if a valve closes rapidly then the bladder isn't going to do anything to help soften that blow. Makes sense. It also kind of seems like the bladder wouldn't like being at a higher pressure than the water? But maybe not.

Looking at the motorized ball valves they have a 5 second closing time. Would this be enough to ramp things down slowly enough to prevent water hammer and slamming the check valve shut?

Anyway these are important issues I would not have thought of on my own, thanks! I do think I'll need to look at maybe the 15SQ or a 10SQ with more stages, though, to get the flow I want for both cisterns with the CSV set at say 30psi for a 20/40 switch since I do have the additional head for getting to the cisterns. If there was just one cistern at the well head I could probably get away with the current pump.

I only see the highest cistern at 20' or 8 PSI above the other. The 30 PSI setting of the CSV will easily take care of both cisterns. You will still need to limit each cistern to 6 GPM to prevent more than 12 GPM being pumped when both cisterns are calling for water. This will keep the CSV pressure at 30 PSI and it won't go below 18 and cause water hammer. With 18 PSI air charge in the tank, anytime you go below 18 or come back up to 18 there will be a water hammer as the diaphragm is stuck to the bottom of the tank.

The 15SQ would do 17 GPM, so each cistern would need to be throttled to about 8 GPM.

5 seconds is plenty close time if you have the cistern throttled to 6 GPM. It won't be enough time if the pressure goes below 18 PSI. I still think a solenoid valve with flow control is simpler, less trouble, and less expensive than a ball valve.

 

[Valveman]

Yes I like the adjustable nature, and of course it has a much bigger range, too.

Makes sense the CSV would need to be placed before the tee. I guess I wonder if having the tank and switch would cause any problems for the CSV or if would still buffer water hammer reasonably well.

Can you give a clearer answer on how to read the tables for the CSV1A on your website? The reason I ask is not because of this well to cistern system where the flows are fairly low and the pressure is not super important, but for the pressure system that is downstream of the cistern serving house and garden. Since that will have higher flow requirements (15-20gpm) and pressure standards, it makes a big difference is the friction loss and pressure falloff are COMBINED compared to only one being relevant.

Restricted to 6 or 8 GPM, friction loss to the cistern is basically a moot point.

For the booster pumps in the cisterns a 15SQ10-220 will pump about 18 GPM at 50 PSI. For this higher flow the CSV1A can be adjusted up to make up for pressure falloff. Setting the CSV at 60 while using a 50/70 switch, the CSV1A will still deliver 18 GPM at 50 PSI. There will be less than 10 PSI friction loss, which the 15SQ can easily make up for.

The CSV125 has no reduced pressure fall off and almost no friction loss. But with less than a 20 GPM pump you probably can't tell the difference, and the CSV1A is longer lasting and adjustable.

I know you like the idea of cisterns, and you may still need one for the other party involved. But pumping directly from the well with like a 1HP pump would be more efficient than double pumping with two 3/4HP pumps.

 

[chickenranch]

I know you like the idea of cisterns, and you may still need one for the other party involved. But pumping directly from the well with like a 1HP pump would be more efficient than double pumping with two 3/4HP pumps.

Frankly I would rather do without them, but my highest priority is protecting the borehole and it doesn't seem to be the strongest. So I don't want to pump directly from it since flows would be higher than recommended by the driller in that case.
But I totally agree re: efficiency, and if weren't sharing the well I would just do the one pump capped at 12-14gpm and be done with it.
That said, I need the cisterns to buffer the high flow events. We could share a cistern, but we're building everything ourselves - including a house and off grid solar system - and we probably won't get to building any cisterns for a couple years. The neighbor is a few years from even thinking about building, so for the time being we will actually just be pumping directly from the well but limiting flow to 10-12gpm.

I only see the highest cistern at 20' or 8 PSI above the other. The 30 PSI setting of the CSV will easily take care of both cisterns. You will still need to limit each cistern to 6 GPM to prevent more than 12 GPM being pumped when both cisterns are calling for water. This will keep the CSV pressure at 30 PSI and it won't go below 18 and cause water hammer. With 18 PSI air charge in the tank, anytime you go below 18 or come back up to 18 there will be a water hammer as the diaphragm is stuck to the bottom of the tank.

This really confused me for a few hours and I had to get my head back in the CSV/pressure/pump world. But now I get it - I think!

This is how I understand it: even with the CSV, the pressure at the pressure switch is only going to be the backpressure in the pipe that is equal to the head required to get water into the cistern. And even the higher cistern is only going to get close to 20psi if it's like 300 feet away and running at 12gpm. So my understanding is that I need to restrict the highest flow such that, at that point on the pump curve, the pump is producing MORE than the total head from pump to pitless plus the cut in pressure on the tank. So at 12gpm that would be 135' +20psi. But with a 20/40 pressure switch and CSV set to 30psi, I want to pump to produce at least 135' + 30psi at 12gpm, or whatever my desired flow is.

Then, with the tank/switch between the CSV and a flow restrictor, you have a nice little stable pressure zone at 30psi so everything is happy. But I see now that without a restriction, the CSV can't create a 30psi zone because that extra pressure is just blown off when the water empties into the cistern.

Is that right?

I think I would still prefer to just put a single 12 or 14gpm dole valve after the tank/switch and let the head difference sort out flow between the two cisterns. Mostly because I know the other user won't be running high flow and we will, and I want the faster refill when I can have it. I guess the only impact this would have is there would be higher flow at shutoff, not sure how much difference it would make to the components.

 

[chickenranch]

For the booster pumps in the cisterns a 15SQ10-220 will pump about 18 GPM at 50 PSI. For this higher flow the CSV1A can be adjusted up to make up for pressure falloff. Setting the CSV at 60 while using a 50/70 switch, the CSV1A will still deliver 18 GPM at 50 PSI. There will be less than 10 PSI friction loss, which the 15SQ can easily make up for.

In this example, wouldn't the pump need to be producing 18gpm at 60psi for the CSV1A to deliver 18gpm at 50psi?

And since you mentioned booster pumps, I've been trying to decide between using a CM-4 or CM-5 compared to a SQ. Seems like it would be easier to service a pump that isn't in the tank, but being inside the tank gives it automatic cooling (in a flow sleeve).
What would you recommend and why?

 

[Valveman]

so for the time being we will actually just be pumping directly from the well but limiting flow to 10-12gpm.

I wouldn't limit the flow to the houses. Just make sure both houses are aware of the max flow and don't use anything outside the house that will use more than say 6 GPM each. The houses will probably never exceed 5 GPM each. By letting the restrictions of the house like shower and sink be the only restriction, they will see the strong constant 60 PSI. But if you put a flow limiter on the line it will steal the pressure from the showers.

This is how I understand it: even with the CSV, the pressure at the pressure switch is only going to be the backpressure in the pipe that is equal to the head required to get water into the cistern. And even the higher cistern is only going to get close to 20psi if it's like 300 feet away and running at 12gpm. So my understanding is that I need to restrict the highest flow such that, at that point on the pump curve, the pump is producing MORE than the total head from pump to pitless plus the cut in pressure on the tank. So at 12gpm that would be 135' +20psi. But with a 20/40 pressure switch and CSV set to 30psi, I want to pump to produce at least 135' + 30psi at 12gpm, or whatever my desired flow is.

Now you are making my head hurt, but yes. Lol!

Then, with the tank/switch between the CSV and a flow restrictor, you have a nice little stable pressure zone at 30psi so everything is happy. But I see now that without a restriction, the CSV can't create a 30psi zone because that extra pressure is just blown off when the water empties into the cistern.

Is that right?

Again, correct and yes.

I think I would still prefer to just put a single 12 or 14gpm dole valve after the tank/switch and let the head difference sort out flow between the two cisterns. Mostly because I know the other user won't be running high flow and we will, and I want the faster refill when I can have it. I guess the only impact this would have is there would be higher flow at shutoff, not sure how much difference it would make to the components.

That would work and give you a faster refill like you want. I would still adjust the flow control knob on a solenoid valve to 12 GPM. This way it can't throw itself wide open at low pressure and high flow, which will make it close gently. But there won't be higher flow at shut off. The solenoid will gently close when the cistern is full. Then the CSV will close down to 1 GPM to fill the pressure tank, and the pump will only be flowing 1 GPM at shut off. No water hammer.

 

[Valveman]

In this example, wouldn't the pump need to be producing 18gpm at 60psi for the CSV1A to deliver 18gpm at 50psi?

Yes, but that pump will do 18 GPM at 77 PSI. Which means it would still cycle on/off while using 18 GPM if you don't have a Cycle Stop Valve. It is very hard to size a pump perfectly, but a CSV makes it match exactly what you want to do.

And since you mentioned booster pumps, I've been trying to decide between using a CM-4 or CM-5 compared to a SQ. Seems like it would be easier to service a pump that isn't in the tank, but being inside the tank gives it automatic cooling (in a flow sleeve).
What would you recommend and why?

CM 5-4 A-S-A-E-AQQE B-A-A-N​

I think is the size CM pump you need. These are air cooled with a fan. Fans make a lot of noise and may not be enough cooing when sitting outside and ambient temps are above 100F. Also has no soft start. Harder to start from a generator or invertor than the SQ. But the CM is a very good pump.

The SQ is water cooled and with a shroud or flow inducer runs plenty cool as long as water temps don't get close to 100F. 90F is about max you want to run a sub motor in without derating a bit. SQ has the 5 second soft start. Works well with genset or invertor. Probably cost less than the CM as well. Setting it with a well seal in the top of a cistern makes it easy to disconnect a union and pull everything out when needed. They don't weigh much when lifting either.

My 2 cents anyway. Lol!

 

[chickenranch]

That would work and give you a faster refill like you want. I would still adjust the flow control knob on a solenoid valve to 12 GPM. This way it can't throw itself wide open at low pressure and high flow, which will make it close gently. But there won't be higher flow at shut off. The solenoid will gently close when the cistern is full. Then the CSV will close down to 1 GPM to fill the pressure tank, and the [COLOR=revert-layer] pump[/COLOR] will only be flowing 1 GPM at shut off. No water hammer.

Ah so I can restrict flow at the solenoid rather than using an extra dole valve? That would be nice, one less part! I'll look into the irritrol valves you mention. Thanks for sticking through that rather brain-beating water flow question - as I was writing it I was getting confused, ha!

 

[chickenranch]

CM 5-4 A-S-A-E-AQQE B-A-A-N​

I think is the size CM pump you need. These are air cooled with a fan. Fans make a lot of noise and may not be enough cooing when sitting outside and ambient temps are above 100F. Also has no soft start. Harder to start from a generator or invertor than the SQ. But the CM is a very good pump.

The SQ is water cooled and with a shroud or flow inducer runs plenty cool as long as water temps don't get close to 100F. 90F is about max you want to run a sub motor in without derating a bit. SQ has the 5 second soft start. Works well with genset or invertor. Probably cost less than the CM as well. Setting it with a well seal in the top of a cistern makes it easy to disconnect a union and pull everything out when needed. They don't weigh much when lifting either.

My 2 cents anyway. Lol!

I'm planning on building a partially buried pump house for this so hopefully it would stay much cooler than that inside and the noise wouldn't be an issue. I am off grid but have inverters very capable of across the line starts and plenty of power margin - that said, I was considering adding in a soft start because it seems to be my tendency to overbuild everything.

Cistern would likewise be buried and the well water is probably under 60F so it's gonna be in cool water. I was noticing that they cost less plus they have the soft start which is nice, and need less space in the pumphouse - could just be a little pit, instead, with the csv and such.
So it sounds like you would orient it vertically in the cistern? I had been thinking horizontal because one of my concerns with the pump in the cistern is not wanting to pull sediment from the bottom into the pump, as well as trying to minimize the reserve height of the water in the cistern to make best use of the volume. seems like even horizontally I would need to leave about two feet of water in there at all times.
But that's a great idea to have it that way for servicing!

Thanks for all the time you've put into this chat, I appreciate it.

 

[Bannerman]

thinking horizontal because one of my concerns with the pump in the cistern is not wanting to pull sediment from the bottom into the pump,

Below shows a simple stand made from PVC pipe, to allow horizontal orientation of the sub pump while keeping it suspended above the botttom. Although a flow inducer sleeve is not shown, one may be easily included on the pump.

Here is an image showing the fabrication of the flow inducer sleeve.

 

[chickenranch]

Yes, but that pump will do 18 GPM at 77 PSI. Which means it would still cycle on/off while using 18 GPM if you don't have a Cycle Stop Valve. It is very hard to size a pump perfectly, but a CSV makes it match exactly what you want to do.

Question on this: I'm looking at these pump curves for the sq15-10-220 or -180, and they have nice performance at that high pressure/high flow region, but then you look at where you would be if you were using only 1-5gpm and the backpressure is extremely high - like 130psi. I'm not so much worried about the pump, but more about pipes and fittings.
to clarify this would be in a situation where water is being pumped from the cistern to meet use in the house and garden, and would include a csv.

edit: I'm actually more concerned about the back pressure on the hose clamps connecting the pipe to the pump in the well - that seems like the weakest connection point. I guess this is pretty common so it must be okay...

 

[Valveman]

130 PSI is nothing. That is right in the sweet spot for the CSV. The only pipes that will see 130 PSI are between the CSV and the pump. Hose clamps can hold a lot. Especially if you use two of them as recommended and long enough barb fittings for two clamps.

 

[chickenranch]

Okay cool. Don't really have any frame of reference for these kinds of things, thanks.