I have a well that may not be adiquate at normal pressure. Is 20 psi enough? How about 30 psi?

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Boyblue

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I'm trying to limit the volume of water used by restricting the flow using a CSV1A. What is the lowest psi that should be set for a building with bathrooms only (16 of them (shower, toilet & Lav) - 4 on the second floor) and would the fact that it's a 2 story building make any difference?
 

Reach4

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The water pressure would be 4.34 PSI less on the second floor than the first floor if the floors are 10 feet apart.

Why are you trying to restrict the water flow? If it is because you want to avoid running out of water, you should have pump protection in case you do run out of water. If you are trying to save power, then there is another factor to consider.

I don't know how 20 PSI would do. It will not change the toilet flushing ability. I expect it would make the shower head flow lower.
 
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LLigetfa

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Sounds like a half baked idea to me. If the well cannot produce fast enough, put in a large secondary storage tank and pump from it.
 

Boyblue

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Sounds like a half baked idea to me. If the well cannot produce fast enough, put in a large secondary storage tank and pump from it.

I'm actually sure the well can handle the demand but if I can set the pressure to what's basically needed, the well will last longer and it will also be less strain on the drainage system. I'm trying to give these folks a decent shower not a luxurious one.
 

Reach4

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30-50 with low flow shower heads would be a good choice I think. http://www.epa.gov/WaterSense/pubs/faq_showerheads.html These have flow control buttons that make the flow more uniform over a range of pressures. Thus there will be little difference between the flow on the second floor when the tank is down to 30 PSI vs the first floor shower when the tank is at 50 PSI.
 

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Boyblue

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Can I take a 20/40 pressure switch and set it to cut in at 20 and out at 30 and set my flow to 25? Or can I leave it at 20/40 and still set the flow to 25?
 

SHR

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No one is going to be happy with 20 psi. Lowering the pressure to below a usable level is not going to save you anything, just really aggravate your customer. I always use 40/60 switches for adequate pressure to all fixtures. Use low flow options for shower heads, aerators and toilets so everyone will be happier and you will not have a mad customer.
 

Craigpump

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Trying to limit water use through low pressure is stinkin thinkin. If anything, more water will be used to accomplish the same task.

A properly designed and built drainage system won't be adversely affected by normal usage.

If I were your tenant(s) and you cut the water pressure, Id report you to the local health dept right after I found another place to live.
 
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Valveman

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I'm trying to limit the volume of water used by restricting the flow using a CSV1A. What is the lowest psi that should be set for a building with bathrooms only (16 of them (shower, toilet & Lav) - 4 on the second floor) and would the fact that it's a 2 story building make any difference?

The CSV1A can be set as low as 7 PSI. But it takes 10 PSI just to get water to the second floor with no pressure left. The CSV1A will restrict the flow to match the amount being used, no matter what pressure you set it up to run. Just use low flow shower heads and faucets and the CSV will deliver low flow with good pressure.
 

Boyblue

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The CSV1A can be set as low as 7 PSI. But it takes 10 PSI just to get water to the second floor with no pressure left. The CSV1A will restrict the flow to match the amount being used, no matter what pressure you set it up to run. Just use low flow shower heads and faucets and the CSV will deliver low flow with good pressure.
 

Boyblue

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I'm trying to provide housing to folkes that can't afford much. They will likely be moving from a place that don't even have running water so don't judge us based on your lofty standards guys. If 20 psi is too low, tell me what is the minimum reasonable psi?
 

Boyblue

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I would say with two stories 30/50 is as low as you can go.
Ok that's fine. Let me get everything ordered and installed, then we can fight over the settings :)

Actually there's one more thing, the CSV1A only goes to 25gpm. That's on the minimum end of my estimation which is 25 -29 psi. What would be the appropriate CSV for 28-29 GPM?
 
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Reach4

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Here is the revised math after valveman pointed out my big error. These revised numbers are much less worrying. Estimating 6 amps, 240 volts, $0.30 per KWH, assuming a roughly resistive load for calculation simplicity, you will pay about $0.0012 per minute while the pump runs. So I am presuming 1440 watts while the pump runs.

While the pump will draw a little less current when the CSV is applying major restriction, the pump is pumping 3 GPM rather than 15 GPM. Now if you pump 500 gallons at 15 GPM, that would cost you $0.24 per 1000 gallons. If you pump another 500 gallons at 3 GPM, that would cost you $1.20 in electricity. The total would be $1.54. Maybe I made another error or two. If I presume the power consumption drops to 80% during the 3 GPM time, then the $1.20 figure becomes $0.96 for a total of $1.20. Valveman says the power consumption rate drop would be even more than 80% of what it would be at the 15 GPM flow.

If I presume that with a just a large pressure tank, of each 1000 gallons that 500 gallons would be pumped at 15 GPM and 500 at 13 GPM, then I compute $0.24+$0.28 for $0.52 total.

Now is it reasonable to presume that you would pump as many gallons at 3 GPM as at 15 GPM with a CSV? Got a better prediction? I am presuming fairly low flow toilets and no irrigation.

I took great simplifications in calculations. If somebody has less simple but more accurate figures to substitute in, then I would be glad to try those numbers in my spreadsheet. Such as how many amps the pump would be expected to draw while pumping against 35 PSI at 15 GPM vs pumping 3 GPM at whatever pressure would be probable. . http://www.csgnetwork.com/waterusagecalc.html is a calculator for estimating water use per month.

edit: Bahamas power rates bill the fuel costs as a separate line item. With low oil prices right now, the $0.30 per KWH is probably a little high. http://www.gb-power.com/en/home/residentialservices/billing /fuelasurchargecalculation/default.aspx then add $0.1195 to $0.1495 per incremental KWH. http://www.bahamaselectricity.com/rates.cfm
 
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Boyblue

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I thought you were trying to rate limit the GPM by reducing PSI? How is the piping sized? Surely you will have friction losses there too.
We'll probably end up with 35 psi which will put me closer to the top end of my GPM estimate. I'd prefer the pump to be under worked so I'm looking for something in the 28-30 gpm range which puts up over the rating CSV1A.
 

Boyblue

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Here is something that you may want to consider. Estimating 6 amps, 240 volts, $0.30 per KWH, assuming a roughly resistive load for calculation simplicity, you will pay about $0.12 per minute while the pump runs. So I am presuming 1440 watts while the pump runs.

While the pump will draw a little less current when the CSV is applying major restriction, the pump is pumping 3 GPM rather than 15 GPM. Now if you pump $500 gallons at 15 GPM, that would cost you $4.00. If you pump another 500 gallons at 3 GPM, that would cost you $20 in electricity. The total would be $24. Yes, that sounds high to me too. So maybe I made an error or two. If I presume the power consumption drops to 80% during the 3 GPM time, then the $20 figure becomes $16.

If I presume that 500 gallons would be pumped at 15 GPM and 500 at 13 GPM, then I compute $4+$4.63 for 8.62 total.

Now is it reasonable to presume that you would pump as many gallons at 3 GPM as at 15 GPM with a CSV? Got a better prediction? I am presuming fairly low flow toilets and no irrigation.

I took great simplifications in calculations. If somebody has less simple but more accurate figures to substitute in, then I would be glad to try those numbers in my spreadsheet. Such as how many amps the pump would be expected to draw while pumping against 35 PSI at 15 GPM vs pumping 3 GPM at whatever pressure would be probable. Also consider that 1000 gallons per month per person is a fairly modest use and would be rather low use for 2 people. http://www.csgnetwork.com/waterusagecalc.html is a calculator.

Bermuda power rates bill the fuel costs as a separate line item. With low oil prices right now, the $0.30 per KWH is probably a little high. http://www.gb-power.com/en/home/residentialservices/billing /fuelasurchargecalculation/default.aspx then add $0.1195 to $0.1495 per incremental KWH. http://www.bahamaselectricity.com/rates.cfm
 
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