More on Fog Harvesting

Solex roof/fog harvesting system

I have now completed my first fog harvesting system.  It is approximately 200 sq. ft. of surface and captures about 5 litres of pure clean water on average per day when there is fog at night and in the morning.  Materials cost about $2.00 per sq. ft. for construction.  Right now I am not segregating this water, but rather, adding it to the existing rainwater storage tanks.  Since the water is so clean, I might separate it at some point in the future.

The basic collection material is Solexx, a 3 mm thick twin wall UV protected polyethylene that comes in rolls 49.5 inches wide. The material is generally used instead of twin walled Lexan for a cheaper alternative for greenhouses.

In my case I have also installed a gutter on the lower edge to catch the water and transport it to the storage tanks.  I originally bought the twin wall material to cover my pergola just so that I could protect certain cactus and succulent plants during the rainy winter months from too much rain. I was surprised how much fog was condensed onto the polyethylene and dripping onto the surface below, so I added the gutter.

I have also noted that the roof itself is also a fog catcher, but that water is automatically diverted to the same gutters and water storage tanks as the rainwater from the roof. It would be more difficult to segregate the two water sources and its purity might be more of a problem.

Fog Harvesting

I just stumbled onto Fog Harvesting.
I am thinking of setting up a pilot project to see what the cost and yield are for a simple system. If successful I will expand it using my existing storage tanks.  It is completely passive once set up.
It will be interesting to see what yield I get per sq. yd. of material.

Here is another interesting site on this subject. Please comment with what you know about this subject here.

Enclosing The IBC Totes

Above are two pictures of the construction of the enclosure for the IBC totes.  Both picture are from the open end.  The second picture shows the roof sections from above.  Each section is 40" x 10' long.  They lie next to each other with the tar paper overlapping the edge of each section onto the next section.  In this picture there are 5 sections already installed.  That is approx. 200" x 10' or 

16' x 10'.  The first picture shows the same set up from below. Here you can see the tanks.  I have already mounded the wall along the right side between the tanks and the fence.  

With a few more sections I will be done.  The sections are clamped together so that the wind won't blow it away.

For the construction of the roof section I am using very lightweight strips of wood 10'x 3/4" x 1 1/2"

The ribs and ends of each section are 39 1/2"x 3/4" x 1 1/2". Stretched over the frame is a section of plastic fencing material 10' x 40" and above that is the 40lb. roofing material. You can see the sag in the lower photo, but that will be supported so that the span will only be about 5' between the support on the higher tank and the fence.

Fortunately I don't have to deal with a snow load, but I do have to be concerned with rainwater load and wind.  I am installing the sections so that there is a drop of 1/4" per foot so drain the water to one side.  I am using cheap general purpose alligator clamps to hold the sections together so they don't blow away in the wind.

If I have to remove a tank for servicing I can easily remove the roof sections and gain access.

As I add the sides I will shoot some more photos and post them also.

Another Alternative for Water Storage Tanks

While I was picking up my IBC Totes yesterday I had a chance to speak with the operations manager at this olive oil importer and distributor.  There were 10s of thousands of IBC totes at this location. Many of them were empty, some were full of balsamic vinegar and some were full of olive oil.  I had mistakenly thought that the olive oil was transported to this location in the IBC totes.  In fact, only the balsamic vinegar which they also distribute comes in the Totes.  The oil, as it turns out, comes shipped in cargo containers that are 20 ft. by 8 ft. and about 8 ft. high.  The container is filled with a heavy duty plastic bladder that will hold 6,000 gallons.  When the container arrives they off-load the olive oil into the IBC totes.  Then they remove the bladder from the cargo container and hang it so that the oil drains out.  They have found no way to dispose of these bladders other than the landfill. They are obviously capable of holding water.  They cost about $1,000 new and are not reused.  They are thrown out.  In the case of the IBC Totes the plastic and the metal can all be recycled, but not so with the bladders because it is so difficult to get all the oil out efficiently. I was thinking that the bladder could potentially be installed and then cleaned in situ with some sort of detergent or degreaser.

The bladders cannot be just placed on the ground and filled with water. I think they must be contained in something -- either a steel cargo container with supplemental bracing from side to side or possibly with just a hole in the ground.

The distributor is going to give me one to experiment with. I think I can get one when it is folded up into a pickup truck.  I don't really want to dig a hole in my yard that is 20 x 8 and 8 feet deep, even if the bladder is free. And I certainly don't want to put a steel shipping container in the yard (I understand these can be had for under $1,000.)  While this would be a bit cheaper than the IBC totes that I have been using, they would be far less flexible and yard friendly.

If anyone has any bright ideas about these bladders please chime in and let's talk about the possibilities.

Installing the Secondary IBC Tote Storage Tanks

The storm this last week dumped just over 9 inches of rain here.  Unfortunately, my primary storage tanks are already full and I could not capture any new water.  This situation will not be lasting much longer.

I have now purchased 20 additional IBC totes (265 gallons ea. x 20 = 5,300 gallons) and the necessary PVC piping to hook it into the remaining downspouts, the irrigation system, and electric cable for the pump. This will bring my total capacity to 6,400 gallons.  The tanks I got this time cost $40 each and the truck rental to get them here added another $5 to the cost of each. (Total cost for these 20 tanks is $900 including transportation.)

The images immediately below are various views of the in process installation.  The most labor intensive part was leveling out three levels of terraces area to hold the tanks and building retaining walls.  As you can see, the lowest level tanks are now in place, there is one tank each at the second and third levels.  I have also used one tank as a short term holding tank for rainwater as it comes off the roof before it is pumped into the tanks.  I had to do this in order to get the water into those tanks since the gravity feed brought the water in too low to fill just by gravity.  I will use the same holding tank to pump the water into the irrigation system when necessary.

This is the holding tank (not hooked up yet)

I have not purchased the enclosure material to cover the tanks nor the pump yet, but will do so very shortly.  I have already trenched out the ditch for the various pipes and electric line to bring the downspout water to the new tank location. I will set the IBC totes in place and lay the drain line within the week.  Unfortunately, the water from the major storm coming this week will not get into my tanks.  This one storm would most likely fill them to the brim.  C'est la vie. It will have to be the next storm that fills them.  I suspect that when all is done I will have spent another $800 for these other materials.  So, total cost will be about $1,700 for the 5,300 gallons.  That's around 32 cents per gallon installed.

For the primary storage tanks I have found it useful to have a valve to redirect the water from the original drain to the IBC totes.  This is useful when the tanks are completely full.  The overflow for those tanks can't really handle multiple storms.  It just wasn't built for that.  Given the success I have had with this method, I think I will do the same with the secondary storage. (By way of explanation the primary and secondary storage systems are on opposite sides of the house and pick up the water from different downspouts, so I do need two such valves, unfortunately, since they are somewhat expensive).

I found it difficult to find out where the existing underground drainpipe is under the yard.
I have found it useful to have an electrical snake to insert in the drain at the point where the downspout goes into the ground in order to determine how far it is to the first elbow or tee in the drain.  That way, once I know the direction the drain is going I can determine where the pipe is underground at the change in direction.  This doesn't answer every question, but was useful in cutting down on the number of test holes I had to dig.

Since I am going to be stacking the totes (2 high) and the location is not that far below ground level I am going to have to pump the water up into the tanks when it rains.  I will use a sump pump with an automatic on/off switch that is activated by the water level.  I am going to use this same pump to pump water into the irrigation system in order to get the pressure that I need to run through that system.  I will have to have a few valves to open and shut in order to accomplish this.  Haven't worked it all out completely yet, I will post a sketch of how it finally ends up in case you are interested.

I have not been too happy with my filtration system on the primary storage tanks.  I have had to clean it out from getting clogged up three times already.  The very fine grit is coming off my roof and really does a number on the filters.  I have probably removed 20 lbs. of this stuff already since the rainy season started in September.  I think I will just have to clean it out after each rain (2-3 inches of rain).  It only takes a few minutes so it isn't the end of the world, given how much water I am harvesting.

One further note, when I put in the trench to divert the rain water to the secondary set of totes, I inadvertently went slightly uphill in one section.  This was just enough to prevent the water from flowing by gravity to the new tanks.  Consequently, I have dug the trench a little deeper in that section to avoid this problem.  I should have known that water will not run uphill, unless it is a siphon or under pressure.

Protecting the IBC Totes from Light

I am actively working on the secondary water storage system.  I am going to be adding 20 tanks in two rows of 10 tanks, with 10 on top of the 10 on the ground level.  I have already cleared and leveled the area that I want to place the tanks. It is located next to a fence (6 feet high). The tanks will be almost 8 feet in height, so I am going to raise the fence another two feet to act as the light barrier on that side.  I will still have to protect the tanks from light on all the other sides.

On the primary tanks I used hardy board and steel stakes hammered into the ground to construct the shell.  I think that for this bank of tanks I will try to use a more simple and cost effective material.

Let us review the situation.  We have to protect the tanks from UV light infusion or else we will have algae buildup in the tanks and deterioration of the polyethylene tanks themselves.  Next, the material that we use for this purpose must be able to withstand the damage that UV light can produce.

One of my neighbors, who is also installing rainwater  IBC totes, found these covers:

The website for buying them is here. They sell for about $60 each, depending upon exactly how many you buy.  I personally think that is expensive and I am concerned about their durability.  The website says that they are made of a PVC material.  My understanding is that while the PVC may be good for protecting the inside from UV light, the material itself is not durable for UV applications (i.e., the material will deteriorate if exposed to UV light and will have a short lifespan).  I have not verified this last suspicion.  That having been said, I thought I would include it here for those of you who have any sewing skills.  I am researching materials that could be used and will post anything I find that is interesting. Note, if sewing fabric to assemble a Tote caddy, please use the special UV thread that is available (used for outdoor cushions) or you may have durable material coming apart at the seams as the UV deteriorates the thread more rapidly than the fabric.

I have found a high impact polystyrene (black) that would make a wonderful outer shell, but I still have to figure out how to seam it since you could not use a sewing machine for this.

I did find this YouTube video that describes using black plastic sheeting. I again stress that the material used must be able to withstand deterioration from UV light.  I don't think the material used in this video is that type of material.

Gray Water Irrigation System

The construction of the gray water irrigation system here at the house is functioning on an experimental basis and is almost completed. We have departed from the standard or recommended design for the distribution of the water into the garden with this system. We did this primarily because we do not want to create the larger pits filled with mulch or gravel for the water that percolate into the ground as is usually done.  We want to use flexible irrigation hoses with holes in the line near each one of the plants with small gravel or mulch basins near each hole in the flexible water hose.  We think this will be more efficient, but the holes may get clogged. We still consider this approach very experimental. I will report on the success of this method once we have it working with a little time under our belt operating it.

The gray water that we are capturing is the water from the laundry and one bathtub/shower and the bathroom sink.  We may add one other shower to this system, but that one is used very infrequently and it may not be worth running a pipe that far (Note: I may add that shower as an alternative to my taking a shower in the bathtub). Also, we do not think that we can effectively use that additional water as it might exceed the capacity of the system. Also, we are not adding the gray water from the master bathroom because it is on the second floor and we would have to open up too many walls to separate the gray water from the black water.
We have decided to bathe downstairs so that we can capture this gray water.  This will be primarily during the summer months when we have the largest need for water in the garden and very little rainwater.
(Note: this comment was added after the system had been installed and was running for a while.  Now that the system is operational, I am running the drain line from the shower to the gray water systems.  This will not increase the load on the system as I will be not taking a shower in the bathtub and, instead, showering in the shower stall.  Total cost for the additional run turned out to be about $15. 00 for the convenience of taking the shower there.)

Capacity

We do about six loads of washing a week, at 15 gallons per load. We have a front loading high efficiency washing machine. Figure about 90 gallons a week for this.  For this system, however, it will be far more meaningful to talk about daily usage, since we do not want to flood the garden with too much gray water at one time.  We normally do no more than two loads in the washing machine a day (2 loads = 30 gallons).
There are two of us in the house and we either take a shower or a bath. Figure about 20 gallons for a shower (my showers are usually only 5 minutes long and should only use about 10 gallons) and about 30 gallons for a bath. I generally take the quick shower, my wife tends to take the bath.  So, figuring that on a typical day we each bathe, that is another 50 gallons of water or less. I have to assume for computing the capacity that this is on the same day as the 30 gallons or water for the washing machine.
In summary, for a typical day when the laundry is done we might use:
Washing machine                  2 loads                   30 gallons
Bath                                        1                            30 gallons
Shower                                   1                            20 gallons

Total                                                                     80 gallons

Now, we know that this is not going to be all used at one time, so we are going to build the system to handle a maximum of about 40 gallons in one hour.

Gray Water Storage Capacity

It is not a good idea to store gray water for more than a day.  We want to merely store that larger quantity of water for, say, at most an hour or so to let it permeate the ground, instead of running off on the surface if it is discharged too rapidly.  We are building the system to handle about 40 gallons an hour, but do not expect to be using 40 gallons in one hour very frequently (at most 3 times a week), and most other times there will be no or very little water going through the system.

The Garden

We have chosen a large succulent and cactus garden that we have constructed that we currently hand water.  The Garden is about 320 sq. ft. in size.  It is located downhill from the house and about 60 feet away from the house.

The Storage Tank

We have departed from the typical storage tank concept and decided to use the drainage pipe itself as the storage device.  There are approximately 55 feet of 4 inch diameter drainage pipe once the water leaves the house.  There is also about 20 feet of 2 inch pipe running along the foundation leading down to the 4 inch pipe.  The storage capacity in the pipe is as follows:

55 ft. of 4 inch pipe  = 4.80 cu. ft.
20 ft. of 2 inch pipe  =   .44 cu. ft.
Total capacity              5.24 cu. ft. = 39.20 gallons

Water Distribution to the Plants

At the base of the pipe just as it approaches the garden from the house we have installed a large irrigation box. You can see the green cover plate for that box in the picture above. Immediately before entering the irrigation box the pipe changes back from a 4 inch pipe to a 2 inch pipe. In the box we have an inspection window in the pipe made from clear plastic tubing the same diameter as the pipe.   Then, following the window there is a manifold.  The header is made of 2 inch plastic pipe. We have drilled  5  holes, each  3/4 inches in diameter into the manifold and inserted nipples and connected the black flexible 1/2 inch irrigation tubing to the nipples.  The flexible tubing weaves between the plants underground (Note: since I am still experimenting the tubing is above ground as you can see in the picture above). Also note that there are a number of bends in the pipe within the irrigation box so that I could fit it all in there.  Obviously, if you have a different setup you may be able to do this without all the elbows I had to install.

The flexible tubing has holes near each of the plants to be watered.

The amount of water that will be distributed to the plants on a square foot basis is computed as follows:
If you assume that he water is distributed evenly over the 320 sq. ft. area of the garden, then, on laundry day (80 gallons of water)  the amount of water per sq. ft. will be equal approximately 10.5 cu. ft./320sq. ft. = .033 cu. ft../sq. ft. To compute the equivalent rainfall this must be converted to inches. This is 57 cu. in./sq. ft., which translates into the equivalent of .4 in. of rainfall. Since this distribution method will not distribute the water evenly, we are estimating that the equivalent for the areas that are actually receiving the water will be more like the equivalent of 1/2 in. of rainfall.  Ideally this level will be achieved at least three times a week, with smaller amounts on days when only the bathing occurs.

Percolation of the Water into the Garden

There are two inspection windows made of clear plastic 2 inch pipe. One window is attached to the manifold down by the garden (see above picture) inside the irrigation box that we just discussed above, and the other is just at the point where the pipe leaves the building (see picture below).

This is exactly the area between which there are about 40 gallons of storage capacity.  With the bathtub full of 40 gallons of water I can now test to see how long it takes for the storage pipe to empty (I considered installing a valve in the irrigation box that would allow me to store all the water above the valve, but opted not to do it for fear that I might forget to open the valve when required and thereby cause a backup into my house.)
(Note: Now that the system is in I think it might have been better to put in a bib valve so that I might take water from the garden hose to connect to the system so that I might use the irrigation portion of the system without having to do laundry or take a shower.  The only alternative I have without changing the system is to put water into the bathtub and let it flush through the system.)

Gaging from the time it takes to percolate into the ground with a limited number of holes I have now computed that it takes about 10 holes to percolate 40 at gallons per hour. I have installed about 40 holes, so it takes about 15 minutes to distribute 40 gallons of water.

The flexible irrigation pipe is exposed for testing purposes.  When testing is completed the hose will be buried and mulch or gravel will be inserted around all the outlet holes near the plants.

Cost

The cost of the project has been about $200 in materials.  It took a few days to install.

Other Considerations

I have not yet installed either a bypass valve or an overflow for the system.  These matters concern me and I will be addressing them.  The main problem with the bypass valve is that I must install one that is electrically controlled as the place where the valve must be located is in the crawl space below the house. More on this later.

last modified 8/17/2014