ro water saving idea

So i guess your not amazed :lol:

This way is less money up front, and less waste water. As far as I can tell it a Win Win.

In Atlanta their is even a second surcharge rate during these months if you go over 15000 gallons a mo. it's like $5.50 /1000.

Bean you are a wealth of info, so how about some help with the flow rate question. What do you think the water flow rate of a .17" orifice/1/4"hose ID is at 50 psi? Can you stear me in the right direction to find this info?
 
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Thats is kind of a tough one for me.... but I will give it a stab.

Lets assume Polyethelene hose with a friction constnat of 0.000039 (looked up):

The .25" ID hose at 50 PSI and 10 feet will flow somewhere in the neighborhood of 27ft/sec or about 4 GPM. Working backwards with the calculated flow and velocty gives us a 48 PSI pressure drop... sounds about right I guess.

Now adding the .17" orifice is what I am not sure about... It would appear the the static pressure would increase (less pressure drop due to the orifice backing the fluid up in the pipe). My handy black book tells me that the flow would be about 2.8 GPM with an orifuce that reduces 1 pipe size (.35 to .17 seems close enough).

I think a fluids engineer would be able to get you closer... I am by no means a fluids expert or an engineer, I just slept at a holliday inn last nite.
 
There is a lot of software out there that does this sort of thing (most of it is expensive....) I would poke around a few engineering forums and see if you can dig up an answer ...it's not just fish people that use forums to yak at each other :)
 
<a href=showthread.php?s=&postid=7591084#post7591084 target=_blank>Originally posted</a> by yourfishman
thanks jdieck, this seems to be a incomplete statement. thier needs to be a flow rate for this to be correct and have any value.

bean you got a formula for this. im a little suprised that i cant find this info.

1/4" RO hose ID is .170". How much flow can go though that small of a hose at the various psi's? (40, 50, 60, 70, 80,) Is their a chart anywhere?
Click to expand...

Ok You want it you got it although IMO it is irrelevant given the pressure drop across membranes and filters and the relatively low velocity of the water.

This assumes two 75 gpd membranes at a 4:1 waste to product ratio connected in series for an estimated 5:2 waste to product overall ratio
at the highest flow rate point which is the inlet of 7 times production per membrane.

Case 1:
Pressure 30 psi
Production per membrane 40 gpd (280 gpd inlet flow)
Pressure drop per foot of 1/4" line 0.0138 psi

Case 2:
Pressure 40 psi
Production per membrane 60 gpd (420 gpd inlet flow)
Pressure drop per foot of 1/4" line 0.0507 psi

Case 3:
Pressure 50 psi (nominal specification for Filmtec 75)
Production per membrane 75 gpd (525 gpd inlet flow)
Pressure drop per foot of 1/4" line 0.0742 psi

Case 4:
Pressure 60 psi
Production per membrane 90 gpd (630 gpd inlet flow)
Pressure drop per foot of 1/4" line 0.101 psi

Case 5:
Pressure 70 psi
Production per membrane 108 gpd (756 gpd inlet flow)
Pressure drop per foot of 1/4" line 0.139 psi

Do you need the Reynolds Number? :D
j/k
 
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<a href=showthread.php?s=&postid=7591284#post7591284 target=_blank>Originally posted</a> by yourfishman
So i guess your not amazed :lol:

This way is less money up front, and less waste water. As far as I can tell it a Win Win.

In Atlanta their is even a second surcharge rate during these months if you go over 15000 gallons a mo. it's like $5.50 /1000.

Bean you are a wealth of info, so how about some help with the flow rate question. What do you think the water flow rate of a .17" orifice/1/4"hose ID is at 50 psi? Can you stear me in the right direction to find this info?
Click to expand...

Just tested the 1/4" tubing with a 1/4 x 1/8 fitting at 100psi and it produced 1/2 gallon of water in 33 seconds or 54.54 gallons per hour.


Jim
 
ohh I did not read the question correctly... back to the calculator...

Lets do 5 Feet of polyethelene hose first: Results are in GPM and assume a level open ended hose (no head, no orifice)

10 PSI = .88 GPM
20 PSI = 1.3 gpm
30 PSI = 1.63
40 PSI = 1.92
50 PSI = 2.17
60 PSI = 2.4
70 PSI = 2.62
80 PSI = 2.82
90 PSI = 3.0
100 PSI = 3.2


Lets do 10 Feet of hose
50 PSI = 1.47
60 PSI = 1.63
70 PSI = 1.78
80 PSI = 1.92
90 PSI = 2.05
100 PSI = 2.17

As you can see as pressure increases in this small ID pipe, the velocity drops off in a non linear fashion (compared to input pressure). This is due to turbulance increasing as pressure increases (The Reynolds number at work).

Bean
 
<a href=showthread.php?s=&postid=7591084#post7591084 target=_blank>Originally posted</a> by yourfishman


1/4" RO hose ID is .170". How much flow can go though that small of a hose at the various psi's? (40, 50, 60, 70, 80,) Is their a chart anywhere?
Click to expand...

By the way it is not how much flow can go through the line because the line pressure drop is not the limiting factor but the restrictor and membrane itself.
Because the flow is determined by the production and waste of the membrane at the different pressures and not really limited by the pressure drop of the line in reality the question is how much product (or input flow including waste is required) for the membranes operating at those different pressures.
Once you get the flow from the membrane specification sheets you calculate the pressure drop.
 
Bean our water costs six cents per gallon just water and waste. At that rate I pay for the membrane, housing, and fittings, in 14 months. If I lived in Pittburgh I would pay for it in 11 months. My current membrane is over three years old and still producing. In the process I save 7000 gallons of waste water.

Jim
 
<a href=showthread.php?s=&postid=7588382#post7588382 target=_blank>Originally posted</a> by jdieck
I think the issue is to avoid water waste rather than pay back of the extra membrane.
A second 75gpd membrane will save about 2 gallons of waste per gallon of produced water.
Assuming the cost of water to be (as in my case) 0.5 cents per gallon the savings will be one cent per gallon of product water. Assuming the cost of a second membrane to be $75.00 you will need to produce 7,500 gallons of product water to break even.
In other words a heavy user like myself with 55 gal per week will need 136 weeks (roughtly 11 years!) to pay it back :D
But again the benefit is saving water plus of cource doubling the system capacity. In my case filling a 55 gal container after a water change in just 9 hours rather than 18 hours. This has been very convenient for me as I travel a lot and always leave a full drum of mixed water for emergencies when I leave. I change water Sunday morning, and by the end of the day I have a new drum ready with newly mixed water before I leave on Monday.
Click to expand...

I do not know how the heck did I get 11 years converting 136 weeks :rolleyes:
So correction pay back for me is in 2.62 years!
so if the membrane lasts 5 years the investment makes sense.
 
My test was done with 4 feet of tubing and the unrestricted pressure may have been much higher.

Yourfishman is only looking for 25 GPH so the 1/4" tubing with beans figures or mine is no problem.

FilmTec 75 GPD membranes can handle up to 2 GPM.

Jim
 
<a href=showthread.php?s=&postid=7592177#post7592177 target=_blank>Originally posted</a> by fahz
My test was done with 4 feet of tubing and the unrestricted pressure may have been much higher.

Yourfishman is only looking for 25 GPH so the 1/4" tubing with beans figures or mine is no problem.

FilmTec 75 GPD membranes can handle up to 2 GPM.

Jim
Click to expand...

Agree. 600 gpd will be the input flow (actually more like 525 to 630 for a range of 50 to 60psi) At that flow the pressure drop per foot of 1/4 line is 0.1 psi.
Assuming 10 ft line that will be 1 psi pressure drop of line and my best guess will be another 2 psi due to fittigs for a total drop of about 3 psi. which IMO will work well and changing to 3/8" does not worth the trouble just to prevent a 3 psi drop.
Considering the pressure drop on sediment and carbon you will require between 60 and 70 psi at the tap for the membranes to operate at the 50 psi specification specially the third membrane which is the one seeing the highest pressure drop.
 
That is correct.... the pressure over the flow restricor and membrane are the limiting factors... So there really is no pressure drop over the hose and other compenents. They are held at a static (or fairly close) pressure due to the fact that they are not the restriction.

Also my numbers were from a pipe flow calculator... They are ballpark but seem to be much higher than fahz tested. Could be a lot of reasons that our numbers don't jive.... it's not that important and they should be close enough.

Fahz... 6 CENTS per gallon? That is 60 Cents for 10 gallons or 6 Dollars per 100 Gallons... 60 per thousand gallons. So my Avg 3000 gallon water bill (we use less water here than most people) would be $180? That simply does not sound right. I just read someplace about your new high quality water system and the wonderful savings your local utilities pass on to the customers?

Like I said I have read a lot of reports on our high water prices here and never heard mention of Minnesota being thousands or percent higher. Shrug... I guess you pay the bill and would know.
 
<a href=showthread.php?s=&postid=7592767#post7592767 target=_blank>Originally posted</a> by BeanAnimal
......Fahz 6 CENTS per gallon?..... . That simply does not sound right. .
Click to expand...

The figure seems off by 1 decimal. Without accounting for drain charges, I think that depending on the amount of excess over the minimum the average water and sewer charge is more like 0.8 to 1.0 cents per gallon considering that the minimum charge is 1 cent per gallon and the excess over the minimum is 0.7 cents per gallon.
Also seems that for 2007 the rates will be increased. The minimum by 2.6% and the excess by 7.3% "ouch!"
http://www.pgh2o.com/fees.htm
 
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<a href=showthread.php?s=&postid=7591790#post7591790 target=_blank>Originally posted</a> by fahz
Just tested the 1/4" tubing with a 1/4 x 1/8 fitting at 100psi and it produced 1/2 gallon of water in 33 seconds or 54.54 gallons per hour.
Click to expand...
jim, your right about concedering the 1/8" fitting on the membrane housing. i thought all the fittings were 1/4". so im a guessing that the ID of that fitting is .125" and is the most restrictive point in the whole system.(aside from maybe the membrane) if it flows 54gph at 100 psi at 50 psi it should be over 30 gph.
i just wanted to make sure that the booster pumps are used to boost membrane pressure and not overcome restrictive hose or fitting sizes. lot of good info thanks guys,

jdieck, i do Aquarium maintenance... hopfully be needing more water in the future.
 
<a href=showthread.php?s=&postid=7593279#post7593279 target=_blank>Originally posted</a> by yourfishman
jim, your right about concedering the 1/8" fitting on the membrane housing. i thought all the fittings were 1/4". so im a guessing that the ID of that fitting is .125" .....

jdieck, i do Aquarium maintenance... hopfully be needing more water in the future.
Click to expand...

Well regarding the measurment it is not so. Put the blame on the engineers that set the standards without knowing what a ruler is but believe it or not the ID of a 1/8" MNPT fitting is even larger than the ID of a 1/4" tubing.

I also hope you use more water :D

pipe_dim.gif
 
Your right I was wrong I pay 8 CENTS not 6 cents. $2.01 for 100 cuft of water and $4.04 for 100 cuft of waste not including other charges. If 100 cuft is 748.05 gallons that's what I pay. Water is cheap it's the waste water that is getting us. We can't meet EPA Standard because of storm water run off in our waste water. My meter is read monthly and I use 5 cuft of water a month for $30.25 not including fix charges, storm water or taxes. I live on Lake Superior one of the largest fresh water lakes in the world.

Jim

<a href=showthread.php?s=&postid=7592767#post7592767 target=_blank>Originally posted</a> by BeanAnimal
That is correct.... the pressure over the flow restricor and membrane are the limiting factors... So there really is no pressure drop over the hose and other compenents. They are held at a static (or fairly close) pressure due to the fact that they are not the restriction.

Also my numbers were from a pipe flow calculator... They are ballpark but seem to be much higher than fahz tested. Could be a lot of reasons that our numbers don't jive.... it's not that important and they should be close enough.

Fahz... 6 CENTS per gallon? That is 60 Cents for 10 gallons or 6 Dollars per 100 Gallons... 60 per thousand gallons. So my Avg 3000 gallon water bill (we use less water here than most people) would be $180? That simply does not sound right. I just read someplace about your new high quality water system and the wonderful savings your local utilities pass on to the customers?

Like I said I have read a lot of reports on our high water prices here and never heard mention of Minnesota being thousands or percent higher. Shrug... I guess you pay the bill and would know.
Click to expand...
 
<a href=showthread.php?s=&postid=7593546#post7593546 target=_blank>Originally posted</a> by fahz
Your right I was wrong I pay 8 CENTS not 6 cents. $2.01 for 100 cuft of water and $4.04 for 100 cuft of waste not including other charges. If 100 cuft is 748.05 gallons that's what I pay. Water is cheap it's the waste water that is getting us. We can't meet EPA Standard because of storm water run off in our waste water. My meter is read monthly and I use 5 cuft of water a month for $30.25 not including fix charges, storm water or taxes. I live on Lake Superior one of the largest fresh water lakes in the world.

Jim
Click to expand...

I think you mean you use 500 cuft of water a month, or a total of ~3700 gallons (I used 741 gallons/100cuft). That comes out to $0.0087/gallon, so you pay less than a penny per gallon, not 8 cents a gallon.
 
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