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FBBP
Veteran Member
Posts:1215
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| 15 May 2012 11:40 AM |
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Clark - that makes good sense especially if you already have the checks in place.
Bob |
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Clark
Basic Member
Posts:248
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| 11 Jun 2012 09:06 AM |
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My rainwater harvesting system is nearly ready to go operational. Picture #1 shows the interior of the 3500 gallon cistern with sump and submersible pump. The ICF walls and concrete floor are sealed with a rubberized paint (Ames Blue Max). Picture #2 shows the associated plumbing in the basement. Note the blue PEX tubing which connect to the toilets. The rainwater harvesting plumbing is isolated from the municipal water supply using a reduced pressure backflow preventer which is located between the floor joists (not visible). --Clark   #1 #2 |
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Clark
Basic Member
Posts:248
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| 15 Jun 2012 04:45 PM |
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With my rainwater harvesting system now complete, I can report that the total out-of-pocket material cost came to $2988. There's no labor in this cost since it was a 100% DIY project. With a capacity of 3500 gallons, that breaks down to $0.85 per capacity gallon. At current water rates charged by the city, breakeven requires the collection of 270 tankfuls of rainwater (nearly 1 million gallons). Based on the average annual rainfall in my area, the maximum rainfall I could expect to collect per year for my roof area at 90% collection efficiency is about 15 tankfuls. Thus, breakeven at today's water rates will be at least 18 years! Clearly, it's difficult to justify the expense of rainwater harvesting on a purely economic basis in my locale (northern Illinois). Anyone interested in a cost breakdown can PM me.
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MikeSolar
Basic Member
Posts:376
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| 18 Jun 2012 06:13 AM |
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I just finished a small job where I put a 2000L cistern into the ground and PV pumped the water (20w pv panel) to a 20GAL pressure tank.
The pressure varies from 10-40psi depending on sunlight and pumping time. The water is used only for 1 Toto toilet and one old Maytag washer. The client may get a new front loader but we are not sure how it will react to lower pressure.
I will put a pressure sensor on to a 3 way ball valve that lets city pressure in if the cistern is empty but I haven't determined the switch over pressure yet. |
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ICFHybrid
Veteran Member
Posts:3039
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| 18 Jun 2012 09:15 AM |
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Mike, can you share with us what the regs are regarding the use of rainwater in that jurisdiction? |
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MikeSolar
Basic Member
Posts:376
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| 18 Jun 2012 01:18 PM |
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I don't, at the moment, know the regs here other than to say that water has seldom been in short supply unless someone disturbs someone else well.
The only issue here is that municipal water is billed and it includes sewage. I you use rain water, there is no revenue for the sewage treatment, therefore it is not allowed. If you are on a well, it is your business.
This is for Ontario, I don't think it would be different anywhere else in Canada.
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Clark
Basic Member
Posts:248
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| 18 Jun 2012 02:29 PM |
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Posted By Clark on 15 Jun 2012 04:45 PM
With my rainwater harvesting system now complete, I can report that the total out-of-pocket material cost came to $2988. There's no labor in this cost since it was a 100% DIY project. With a capacity of 3500 gallons, that breaks down to $0.85 per capacity gallon. At current water rates charged by the city, breakeven requires the collection of 270 tankfuls of rainwater (nearly 1 million gallons). Based on the average annual rainfall in my area, the maximum rainfall I could expect to collect per year for my roof area at 90% collection efficiency is about 15 tankfuls. Thus, breakeven at today's water rates will be at least 18 years! Clearly, it's difficult to justify the expense of rainwater harvesting on a purely economic basis in my locale (northern Illinois). Anyone interested in a cost breakdown can PM me.
One would conclude that I was foolish to invest the time and money to build my rainwater harvesting system. I might never recover my costs. So why is the State of Illinois drawing up legislation to encourage rainwater harvesting? I think the reason is that a gallon of water is worth far more than we're charged for it at the margins. The minimum water bill in my city is $45/month not counting sewer charges. That buys me 175 cu. ft. of water whether I use that much or not. So the first 175 cu. ft. of water I use costs about 3.5 cents/gallon. After that the cost per gallon drops to only 0.3 cents per gallon. This pricing practice masks the true value of a gallon of water and encourages water consumption to such a degree that ordinances have to be enacted to restrict water usage during the summer to prevent overloading the capacity of the city's wells and water treatment facilities. If residents paid the actual cost of a delivered gallon of water, the economic justification for rainwater harvesting would be much easier. I recall reading that the average indoor water usage per person per day is about 50 gallons. For my wife and I that's 400 cu. ft. per month at a price of $50 ($45 for the first 175 cu. ft. + $5 for the next 225 cu. ft.). About 25% of that is for toilet flushing. If toilets were flushed with rainwater, and we were charged a uniform rate per cu. ft. of water, our monthly water bill would be reduced to $37.50, because the value of a gallon of rainwater rises from the current $0.003 to $0.017. For the year, that translates to a savings of $150, just in toilet flushing. Add in the savings of outdoor water use in the summer months and we're looking at savings which significantly cut the payback period for the RWH system investment. Imagine, at the start of each month, paying $10.00 for a gallon of gas up to say 175 gallons after which the cost drops to $1.00 a gallon. What affect would that have on peoples' driving habits? Any flaws in my reasoning? |
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MikeSolar
Basic Member
Posts:376
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| 18 Jun 2012 02:40 PM |
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Posted By Clark on 18 Jun 2012 02:29 PM
Posted By Clark on 15 Jun 2012 04:45 PM
With my rainwater harvesting system now complete, I can report that the total out-of-pocket material cost came to $2988. There's no labor in this cost since it was a 100% DIY project. With a capacity of 3500 gallons, that breaks down to $0.85 per capacity gallon. At current water rates charged by the city, breakeven requires the collection of 270 tankfuls of rainwater (nearly 1 million gallons). Based on the average annual rainfall in my area, the maximum rainfall I could expect to collect per year for my roof area at 90% collection efficiency is about 15 tankfuls. Thus, breakeven at today's water rates will be at least 18 years! Clearly, it's difficult to justify the expense of rainwater harvesting on a purely economic basis in my locale (northern Illinois). Anyone interested in a cost breakdown can PM me.
One would conclude that I was foolish to invest the time and money to build my rainwater harvesting system. I might never recover my costs. So why is the State of Illinois drawing up legislation to encourage rainwater harvesting?
I think the reason is that a gallon of water is worth far more than we're charged for it at the margins. The minimum water bill in my city is $45/month not counting sewer charges. That buys me 175 cu. ft. of water whether I use that much or not. So the first 175 cu. ft. of water I use costs about 3.5 cents/gallon. After that the cost per gallon drops to only 0.3 cents per gallon. This pricing practice masks the true value of a gallon of water and encourages water consumption to such a degree that ordinances have to be enacted to restrict water usage during the summer to prevent overloading the capacity of the city's wells and water treatment facilities.
If residents paid the actual cost of a delivered gallon of water, the economic justification for rainwater harvesting would be much easier. I recall reading that the average indoor water usage per person per day is about 50 gallons. For my wife and I that's 400 cu. ft. per month at a price of $50 ($45 for the first 175 cu. ft. + $5 for the next 225 cu. ft.). About 25% of that is for toilet flushing. If toilets were flushed with rainwater, and we were charged a uniform rate per cu. ft. of water, our monthly water bill would be reduced to $37.50, because the value of a gallon of rainwater rises from the current $0.003 to $0.017. For the year, that translates to a savings of $150, just in toilet flushing. Add in the savings of outdoor water use in the summer months and we're looking at savings which significantly cut the payback period for the RWH system investment.
Imagine, at the start of each month, paying $10.00 for a gallon of gas up to say 175 gallons after which the cost drops to $1.00 a gallon. What affect would that have on peoples' driving habits?
Any flaws in my reasoning?
The only issue i have is from the municipality point of view. Ours determines the cost billed by fresh water consumed. If you use rainwater but it all goes to the sewer, where is the revenue to support the treatment going to come from?
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ICFHybrid
Veteran Member
Posts:3039
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| 18 Jun 2012 10:43 PM |
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Interesting thoughts on water and its relative value.
I think that billing for sewage by amount of water consumed is a relatively new trick to increase city revenue. I seem to remember when sewage rates were set at a flat rate. As the rate increases came faster and faster, many municipalities began billing by the amount of usage in order to make it appear more fair and to give people at least the sense of being able to have some control over the cost. If you use a lot of water for your garden, it doesn't go into the sanitary sewer, now, does it? |
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MikeSolar
Basic Member
Posts:376
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| 19 Jun 2012 07:02 AM |
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In Canada, we don't do municipal bonds for major infrastructure projects like is common in the States so when old stuff needs replacing, it either comes from the tax base or a fee. I think the water based fee is pretty good and it helped push low flow toilets and other improvements.
Older cities are starting to separate storm and sewage but a lot of storm water, in Toronto anyway, still goes into the sewer. It can overflow and have raw sewage going right into lake ontario (rare now, but it used to happen regularly). Then processing potable water is much more expensive.
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Clark
Basic Member
Posts:248
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| 19 Jun 2012 07:42 AM |
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Mike, you are so right. The cost of municipal water is dominated by the cost of waste water treatment. I dug deeper into my city's rate structure and found:
Sewer maintenance - $9/month flat fee
Waste water treatment operation and maintenance- $25.33/month flat fee
Debt service on waste water treatment facilities - $12.23/ month flat fee
That's a total fixed charge of $46.56/mo per household for waste water related costs with no discount for outdoor water usage or long periods of no water consumption. For me, 85% of my monthly water bill is related to the cost of waste water treatment.
My 3500 gallons of harvested rainwater is worth just $11. Personal economic benefits of rainwater harvesting appear to be rather weak.
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Clark
Basic Member
Posts:248
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| 06 Jul 2012 10:08 PM |
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Posted By Clark on 08 May 2012 01:09 PM
In case you're interested, the photo below shows the 1/2 HP submersible pump (Simer 2845G-12) with the DIY flow sleeve attached. I used a section of 4" thin wall sewer pipe to construct the sleeve. The sleeved pump will rest on the bottom of a 2' sump in the bottom of the cistern. I capped the bottom of the sleeve and cut three 1-1/2" holes 6" from the bottom for water inlets. Hopefully, that will lessen the uptake of any silt in the sump that gets past the 2" silt berm surrounding the sump as recommended by FBBP. The sleeve is sealed at the top with a rubber gasket and clamped with a stainless steel hose clamp. Three screws center the bottom of the pump in the sleeve leaving a uniform 1/8" gap around the motor for water to flow past the motor to the pump thereby cooling the motor. The total cost to make the sleeve was about $15.
This sleeve doesn't work! The 4" tube is too small to allow sufficient water to meet the intake demand of the pump. The pump runs, but can't develop pressure when the water level is low in the cistern. So, I modified the sleeve as shown in the following photo (minus the pump) using a section of 6" thin wall PVC sewer pipe. Cistern water enters four 2" diameter holes spaced around the base. It flows along the sides of the pump motor inside the sleeve, cooling it, and enters the intake ports located just above the motor. The water is pumped out the top of the pump through a one-way valve and 1-1/4" PVC pipe. Some say the sleeve is not required in this application, but I decided to follow the manufacturer's recommendation. I suppose it depends on how long the pump runs and the duty cycle. The second picture shows the combination pump/sleeve installed in the sump. This design worked even when the water level dropped to the rim of the sump. Note the 2" high circular ring of aluminum sheet metal surrounding the sump. It serves to prevent most of the silt that accumulates on the floor of the cistern from entering the sump and being pumped into the distribution system.   |
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Clark
Basic Member
Posts:248
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| 19 Jul 2012 10:33 AM |
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My new cistern has been sitting empty for weeks waiting for a significant rainfall. Last night it came during a thunderstorm. We received 1 inch of rain over a period of about an hour. I collected 1700 gallons of rainwater in the cistern filling it close to the halfway mark. I calculated the efficiency of the catchment system at 90%. That is, 90% of the rain that touched the roof found its way into the cistern. That's about what I expected. As you can see in the picture, the water is fairly dirty. There's a lot of fine particles suspended in the water most of which I assume was washed off the roof. I have fine mesh gutter guards and a first flush valve that dumps the first 30 gallons of rainwater, but after weeks of no rain, I figure the roof must have been quite dirty. I'll let the silt settle out before using the water to see if I'll have to add another filter to the distribution system. I currently have a 100 mesh filter to protect my sprinkler heads. That might not be enough for the toilets, however.  You can see the float ball in the picture which is connected to a rod that penetrates the wall above the overflow level. It provides a rough gauge of how much water is in the tank without having to lift off the heavy concrete hatch. During the long rainless period we've experienced, I used only city water to irrigate the landscaping. I'm at the point where I'm now being charged 0.46 cents per gallon of city water. That means that the water collected last night is worth about $8. --Clark |
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ICFHybrid
Veteran Member
Posts:3039
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| 22 Jul 2012 04:03 PM |
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Just to clarify that your city water charges are about $0.046 per gallon, not about a dollar for every two gallons. |
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Clark
Basic Member
Posts:248
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| 22 Jul 2012 04:26 PM |
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Posted By ICFHybrid on 22 Jul 2012 04:03 PM
Just to clarify that your city water charges are about $0.046 per gallon, not about a dollar for every two gallons.
Neither, I wrote "0.46 cents" a gallon which is almost one-half cent per gallon. I should have written $0.0046 per gallon. Thank for clarifying. |
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jonr
Senior Member
Posts:5341
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| 23 Jul 2012 09:46 PM |
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I wrote "0.46 cents" a gallon which is almost one-half cent per gallon. I should have written $0.0046 per gallon. Either one works the same for me :-). Tanks - I'd say that thermal storage is the best use for them. |
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ICFHybrid
Veteran Member
Posts:3039
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| 24 Jul 2012 09:59 AM |
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Neither, I wrote "0.46 cents" a gallon which is almost one-half cent per gallon. Sorry, I wasn't accustomed to seeing the "cents" and it went outside my sphere of perception. ;-) That means that the water collected last night is worth about $8. At market rates, but it is probably worth a lot more if it enables you to maintain a desired lifestyle despite shortages, rationing, etc. Also, people pay money, spend some effort, worry, etc., about having a source of emergency water, even if it is only a few gallons, should some disaster arise. I think you have that covered. |
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Clark
Basic Member
Posts:248
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| 02 Aug 2012 09:08 AM |
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Posted By FBBP on 13 May 2012 08:27 PM
Clark - I'm not sure you need the pressure reducing valve on the cistern side, just set the 45/65 to 35/45.
You were right, FBBP. The pressure reducing valve is not needed. I didn't understand how it works. It assures that the pressure will not exceed the pressure setting at the the downstream side, but it won't prevent the pressure from dropping below the valve setting when there's demand for water. So if the bladder tank pressure is 60 psi and the pressure reduction valve is set to 45 psi, when an irrigation valve opens, the pressure will drop below 45 psi. The valve restricts the flow of water too much. It also makes noise when the water flows through it. |
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Clark
Basic Member
Posts:248
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| 31 Aug 2012 05:38 PM |
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I just wanted to give an update on my rainwater harvesting system after several weeks of testing and operation. I've had to make a few tweaks to get things working well.
I've had three good rainfalls that filled the cistern up (3600 gallons each fill). I discovered that the tank leaked at the joint around the sump pit. It seems that silicone caulk doesn't adhere to polyethylene very well (nor does anything else for that matter). I had to rough up the surface of the sump pit at the rim and apply a liberal coating of Blue Max. That seems to have sealed the joint well.
The pressure switch chattered on cut-in because I installed it too far from the bladder tank. I couldn't move it closer (I wanted it located between the pump and the 100 mesh sediment filter) so I installed a water hammer air chamber right before the switch. That got rid of the on-off chatter that would have destroyed my pump in short order.
Right after a heavy rain, the water is murky and shows up slightly discolored in the toilet bowl. That goes away after a day as stuff settles out in the tank. I noticed that on the third full tank, the rainwater is much cleaner than the first couple of fills. I took that to mean that the drain piping has been flushed out of most of the dirt that had collected there before I installed the gutter guard screens.
The pump cannot be heard when it runs, but the one-way valve (which prevents city water from filling the bladder tank when it's empty) hummed when irrigating the landscaping, but I replaced it with one that doesn't make noise, so now you can hardly tell when the rainwater is being consumed. Switch over to city water when the cistern empties is totally automatic, seamless, and safe from a health standpoint.
All in all, I'm very happy with the system.
--Clark
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jonr
Senior Member
Posts:5341
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| 01 Sep 2012 02:02 PM |
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The only things I know of that bond to PE are 1) melted PE (plastic welding) and 2) flame treatment and then G/flex epoxy.
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