Roofing material and rain water harvesting

We have had water collected from a composition roof at this location tested by an EPA certified laboratory. The water passed (actually far surpassed) all epa, and local requirements for potable water purity after being run through a small slow sand water filter (filter 1). Composition roofing material can be used for rainwater collection. An excellent study was done regarding this issue by the Texas Water Development Board (P.O. Box 13231, Capitol Station Austin, Texas 78711-3231), that further confirms our results. “Effect of Roof Material on Water Quality for Rainwater Harvesting Systems
Report by:
Carolina B. Mendez
Brigit R. Afshar
Kerry Kinney, Ph.D.
Michael E. Barrett, Ph.D.
Mary Jo Kirisits, Ph.D.

A new (composition) roof has been installed on the water collection surface that feeds 3 of the slow sand filters in operation here (filter 1,  filter 5,  and the (very small) diy experimental filter mentioned in the extensive post before this one. According to the best information we have, this roofing material does not have moss killer (zinc) embedded in it. As time passes, we will do tests on the water for copper, and zinc compounds – as these are the most common chemicals used to kill algae, and moss. The MSDS reports that the roofing material contains :

Granules – 20 – 45 NE NE NE

Limestone 1317-65-3 25 – 45 5 mg/m3 – resp.15 mg/m3 – total3 mg/m3 – resp.10 mg/m3 – totalREL: 5 mg/m3 –resp.10 mg/m3 – total

Oxidized Asphalt 64742-93-4 10 – 30 NE 0.5 mg/m3(inhalable fraction, as benzene-soluble aerosol)5 mg/m3 – ceiling (15 min. fumes)

Crystalline Silica 14808-60-7 0 – 10 10 mg/m3 / (% SiO2 + 2) – resp.0.025 mg/m3 REL: 0.05 mg/m3 –resp.

Fiberglass Mat 65997-17-3 1 – 3 1 f/cc – resp. 1 f/cc – resp. REL: 5 mg/m3 – total fibers

Titanium Dioxide 13463-67-7 0 – 4 15 mg/m3 – total 10 mg/m3 – total REL: lowest feasible concentration

It is a “50 year” roof. So far, the water has been quite “clear”, (non-turbid) and not discolored. The shingles are: Timberline® Ultra HD™ Lifetime Shingles

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Slow sand water filter operation and water clarity

A rudimentary test was done yesterday, October 2, 2013,  to evaluate water clarity on all of the filters running here. The filters that have the least restricted output flow also have the clearest water output. Two of the filters that have the output running into storage did not have enough ventilation and the storage containers did not have appropriate overflow outlets; these two had the cloudiest output. The three filters with continuous flow into vented storage have the clearest output. Not sure exactly why yet. . .    more later.

Filter 5, the one with the cloudiest output, was modified so the storage has an overflow drain that is lower (closer to the ground) than  the filter output. As I checked this system out it became apparent that there was very little, if any, flow through the filter because the storage was full and there was nowhere for the water to go as it flowed out of the filter. As of October 2, 2013, water is free flowing out of the filter into the storage containers.

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Uniformity coefficient of sand

To determine the uniformity coeffient of sand (from a chosen source):


First: Take a small sample of the sand and determine the sand grain size(wire mesh hole size opening) at which 60% of this small sample‘s weight passes through the holes in a sifting appratus such as wire mesh, and 40% of it does not pass through the holes in that same sifting apparatus.


Second: Then take another small sample of the same sand. Make sure it is the same weight as the first small sample. Then determine the sand grain size (wire mesh hole size opening) at which 10% of this small sample‘s weight passes through the holes in a another sifting appratus such as wire mesh, and 90% of it does not pass through the holes in the same sifting appratus used in this second sifting operation.


Use the same mesh pattern for the first and second operation. However, the mesh opening sizes in the first operation will be different than the mesh opening sizes in the second operation.


Then know that for an equal weight of sand the uniformity coefficient equals:
uniformity coefficient
the sand grain size at which 60% goes through and 40 % is retained
divided by
the sand grain size at which 10% goes through and 90% is retained


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Water filter test summary

After 4 years of college where I learned (hopefully) how to write about what I observe; and following that, close to 7 years of designing, building, studying, and operating small scale slow sand water filters (often called biological sand water filters); some information has become self-evident:

1. With some basic understanding, common sense, and willingness to pay attention to simple maintenance; It is possible to produce extremely high quality water with a “do it yourself” small scale biological slow sand water filter.

2. Continuous flow of water from the same source through a small slow sand filter will result in the highest quality output. (use an overflow to capture the water that does not flow through the filter immediately, and then just re-introduce it again, no fancy expensive high tech stuff is needed if the operator is willing to add the water manually)

3. Finer sand in a small slow sand filter produces the highest quality output as compared to coarser sand, which does not.

4. A slow flow through a small biological sand water filter produces the best output as opposed to a rapid flow, which does not.

5. Thoroughly washed sand produces better output water, than un-washed sand.

6. It is possible to sift your own sand using inexpensive commonly available sand, resulting in sand size quality that comes close to duplicating “manufactured filter sand”.

7. The output from a “do it yourself” small slow sand filter will vary considerably, depending on the surroundings, input water, and attention to maintenance.

8. Highly turbid (cloudy) water will clog a small slow sand filter very quickly; within days, or even hours.

9. “Cleaning” a small slow sand filter by “wet harrowing” is very easy and takes very little time.

All of the specific details regarding implementation of these concepts can be found in this blog, and the three other water filtration websites that are associated with it.

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DIY 5 gallon slow sand filter update

Update November 25, 2013:

An important observation regarding 5 gallon slow sand filters: They are highly susceptible to disruption from freezing temperature. For the past week all of the 5 gallon filters have been frozen. The temps here, in the forest, have been in the mid 20’s (deg. F) at night and barely above freezing during the day. All work on these 5 gallon filters must now start over, as freezing expands the the surface of the sand and effectively disrupts any biolayer that has formed.  The larger filters, with unrestricted continuous flow,  did not freeze. They are still running.

Update November 15, 2013:

I’ve made another critical mistake on these small filters. I forgot to “rough up” the inside surface of the buckets  with coarse sandpaper.  The inside walls of the buckets i am using are smooth, very smooth – in fact far too smooth, because they are new. This is not good, for filters. (this likely would not happen with some recycled containers, as they may already have been “roughed up” on the inside.)The sides of the container must be rough so the biofilm has a randomly rough surface, similar to sand surface,  to cling to. The problem with the smoothness is that its “slipperiness”allows untreated water to slip down the inside of the bucket between the sand and the smooth plastic surface.  As the schmutzdecke matures on the sand surface it slows down the water flow, but between the sand and the bucket inside wall the schmutzdecke can’t form as fast, or as well, because of the lack of surface area on the smooth surface of the bucket. So the microbes and silt that should remain on the top surface of the sand slip through around the sides of the bucket. This would explain why the output water has been showing more coliform instead of less.  This will continue to happen until the biofilm is able to seal up the space between the sand and the smooth inside of the bucket. The seal will most likely be so fragile, that if the bucket is accidentally bumped, the seal will be broken and untreated water will flow past the sand and into the output.  The irony here is that I had this same problem with the larger filters. I forgot to rough up the inside of the containers. Since I had fixed that problem in the larger filters, they are working much better.

On September 16, 2013 we described an experimental ( very small ) slow sand filter setup that was started running here at that time. We have used 5 gallon buckets as the filter container in both cases (filter 10a and filter 10b) with a sand depth of 9.5 inches. Filter 10b was started October 16.

To summarize the results so far ( this is my opinion based on observation and preliminary field tests): Some water quality improvement has been noted, both biological and physical. Ecoli are removed. Coliform is reduced slightly, but not eliminated. Initially, water clarity and color was improved slightly. The degree of improvement has not increased.

After 7 weeks of running time, it appears that a slow sand filter setup in a 5 gallon bucket using .25mm effective size sand with a flow rate of 1 cup per minute  is, at the very best, only marginally effective at filtering roof water from the roof at this location.  A better situation may be to use fine sand (.15mm effective size) as an absolute must, and a flow rate of less than 1/2 cup per minute. However do look at the results (scroll down at the following link to see the image) of the most recent field test on filter 10a. in the original post. The output water quality has become exceedingly more contaminated as time goes on. Compare this to the 38 inch deep filter 5 tests shown. The filter 5 output is nearly perfect.  Fiter 5 uses the same water source as filter 10a.

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Sustainable water filtration

This blog, and the websites associated with it are an ongoing study of slow sand water filtration, which is a sustainable technology. In view of current events and the general decline of the quality of our environment on a local and global scale; access to safe clean water through locally sustainable technology should be a top priority.

A slow sand water filter can be built from mostly recycled materials, and does not need electricity or petroleum produced energy to operate. Slow sand filters do not need  chemicals added to enable their functionality. Slow sand filters last years and are readily repaired and maintained without the need of non-sustainable resources.  Slow sand water filtration uses naturally occurring biological, and mechanical processes to remove harmful substances from water.

Sustainability is very well described here. Read about sustainability, read about slow sand water filtration; and then make your own decision about how “sustainable” rapid sand filtration, membrane filtration, or distillation really is after reading about those processes also. Look at the component parts used, energy used, and chemicals used and figure out what kind of resources are necessary in each situation.

When deciding if a water filter is sustainable technology, carefully consider:

The renewable, or non-renewable energy source required to produce the device and the pollution created when producing the device.  Is the device recyclable? What resources are used to produce the device? Are those resources renewable? Are people exploited in order to produce the device? How long will the device last? Can the device be repaired locally?Also, consider the same things when investigating the operation of the device. Water is needed by people all the time. If non-sustainable energy is needed always to run the filter, then is it really sustainable technology – even if it is produced in a sustainable manner?

What if there was a water filter that required some energy input to produce (energy that could be renewable energy), but required no resources to operate other than sunlight, gravity and some manual labor (adding water occasionally by hand). And what if this filter was totally reusable, non polluting, locally repairable, and did not wear out? That describes a small slow sand water filter. Think about it.

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Rainwater harvesting is not illegal (lets keep it that way)

Update; March 21, 2014:

We have found that nearly every state in the U.S. allows rain water harvesting by individual home owners. Only a few states have severe restrictions. This could all change if citizens do not stay involved in government business. Anyone with enough money and influence can cause laws to be changed. Hopefully , the information on this blog will help people keep themselves informed with the truth about what is going on in their state governments. If rain water harvesting really did become illegal, as some people want to make it seem,  it would be catastrophic; but for now that is only a looming threat. Let’s keep it that way, in fact, if all states had a law like Texas, we would not have such a looming threat. (Texas has a law that actually makes it illegal to prevent anyone from harvesting rain water.)

We have been researching this intensely since February of 2013. So far after spending over 150 hours actually looking through the state government websites of 48 states, and looking at the research of others on all 50 states in the U.S. it has become obvious that Colorado is the only state where the practice of roof water harvesting, rain water harvesting or rain barrel use is illegal according to state government for some people. Colorado is  has strict regulations that are changing (some people in Colorado are forbidden by law from collecting rain water- those without a well, or water rights), and Ohio has strict regulations. Otherwise we have not found any other state government that makes rain water harvesting by individuals against the law for all citizens in all cases.

On the 48 websites we looked at, we did find that there are nearly incomprehensible regulations on water sources other than rain in most states.  We also have found that any homeowners’ association, any county, or any city may have laws in addition to state laws regarding rain water harvesting (with the exception of Texas, where the right to harvest rain water is guaranteed by law.)


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Slow sand filters in freezing weather

Update December 8, 2013: The temperature got down to 10 degrees F here last night – this was the last measurement we had, it is likely that the temp was lower than that (we are not actually in Seattle, we are way out east and north of the city in the Cascade mountain foothills of northwest Washington state). For a while there was a breeze which put the wind chill below zero for sure. This was unusually cold weather. All of the filters that were running here, including filter 2 and 3, are frozen solid and major damage is expected. It may well be several months before anything can be done, and will likely be the middle of March, 2014 before any of the filters will be producing filtered water output. This cold was a surprise; we did not expect the temps to go this low. The pipes on filter 2 and 3 were wrapped and the pump had a heater, so the water flowing through the system was warmed. This did not help, the filters still froze. When I checked, it looked as if the top surface of the water freezing over caused the float valves to malfunction, which then disrupted the flow of warmed water through the filter. That was the beginning of the end. Once the water stopped flowing everything except the pump froze solid. (The pump and pressure tank were in a heated enclosure) Now most of the pipes will be cracked and the filters will need to be emptied, and new output pipes installed. This is a major setback, and a major learning experience. Temperatures at or below 20 degrees F for more than several days will ruin one of these filters, unless they are kept above 32 degrees F and water flows through them continuously.

It is December 6, 2013 and all the filters here are now frozen, with the exception of filter 2 and 3. It is unsure if they will last much longer. The temp. has been below freezing at night for the past week; and barely 32 degrees F during the daytime. The temp. did not get above 28 deg F here today. Now the conditions are windy here and, and the forecast is for colder weather for the next 3 days. I do not know when the filters will start again; probably not until sometime early next year in January, if we are lucky. After they start, it will take at least 3 weeks until they are working. It is likely to be sometime in February before any more testing is done.

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5 gallon DIY slow sand filter update February 7

It is now February 7, 2014. At this location its been below freezing at night for all of February, and for the past 4 days not above freezing at all. On the 6th of Feb. at about 4:00 am, the low here was 13.5 degrees F (-10 deg C).  All of the filters are frozen solid with the exception of the larger filters 2 and 3. They are being fed with water from the shallow well that is heated by the un-frozen ground here and the pump house has a very small heater to keep the pump from freezing; the water must run continuously or it will freeze in a few minutes at 14 degrees F.  All of the ponds are frozen. It will likely be at least another week before we can continue running water through the filters, and then at least another 3 weeks until we can do another test.  Probably the first part of March at the earliest, weather permitting.

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Drought in the U.S.: What to do?

Water is becoming an issue here in the U.S. for a number of reasons :

Rain water harvesting is a way to store water. Even if it is only used for non-potable purposes, it still helps save potable water. A 1500 square foot roof can catch 3700 gallons of water from 5 inches of rain (allowing 20 percent loss due to evaporation, first flow diversion, and non-smooth roof surfaces). There are 231 cubic inches per gallon.  A 1500 square foot roof has  1500 X 144 = 216000 square inches of surface. Five inches of rain on a 216000 square inch surface is 1080000 cubic inches. Divide that by 231 and you have 4675 gallons of water. Take away 20 percent of that due to surface conditions, evaporation, and needed first flow diversion and you have 4675 – 935 = 3740 gallons. divide that by 5 = 748 gallons from 1 inch of rain. add another 20 percent loss and you have 600 (598.4)  gallons. You can wash a lot of clothes with 600 gallons of water. Think about it. Its not against state law to set up a few rain barrels. Check out the rest of this blog and its accompanying websites for lots of info. 

The runoff from the average house with 6 downspouts could easily fill 6 55 gallon rain barrels from just 1 inch of rain. A slow sand water filter, combined with a first flow diverter, will purify the water so it can be used without the danger of serious contamination.

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