Pure Water Occasional, March 14, 2022
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Happy Almost Spring from Pure Water Products, the Pure Water Gazette, and the Pure Water Occasional.
This issue comes at the end of Winter and, we hope, the beginning of the end of challenging times. The articles focus on the excellent new breed of water filter cartridges that make top quality residential water treatment easy and affordable.
We invite you to visit our websites at any time for the latest information about water treatment strategies. Also, we archive literally hundreds of back issues of the Pure Water Gazette (now called the Pure Water Occasional) that go back to the early 1990s.
A promise: more frequent and more exciting Occasionals are on the way.
Thank you for reading. And sincere thanks from Pure Water Products for your continuing support. We consider our greatest asset to be the many faithful customers who have kept us going over the years. We really appreciate your business!
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Pandemic Relief Has Benefited America’s Water Infrastructure
The American Rescue Plan Act — the relief bill that President Joe Biden signed into law on March 11, 2021 — set aside $350 billion to assist states, tribes, territories, and local governments in responding to financial challenges wrought by the pandemic. Water infrastructure improvements are one of four broad spending categories authorized by the act.
Already at least $10.1 billion in ARPA funds have been dedicated to water systems.
Here is how some states have applied the funds:
- California used $301 million to pay off the water bills of low-income residents who fell behind during the pandemic. The state set aside as much as $985 million to forgive customer debt and it is now accepting applications from wastewater utilities.
- Montana allocated $462.7 million to water and sewer infrastructure.
- Louisiana allocated $300 million.
- Kentucky and Ohio allocated $250 million.
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How Much Nitrate Do Home Reverse Osmosis Units Remove?
Nitrates are a drinking water problem mainly in areas where wells are contaminated from either livestock feed lots or fertilizer runoff. Nitrate is "allowable" officially by regulators at rates up to 10 ppm, but the lower the nitrate content the better. Reverse osmosis is the best and easiest residential treatment.
Factors that affect performance negatively are low water pressure, low pH, and high sodium and sulfate levels.
If water pressure is low, adding a pressure boosting pump to the RO unit will enhance performance. Or, if very low nitrate levels are essential, you can add a nitrate-specific anion cartridge to your undersink RO unit which should assure virtual 100% nitrate reduction. A small nitrate cartridge operating as an RO post-filter will normally have more than enough capacity for a year of service between cartridge changes.
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Emerging Contaminants: The NSF List
The list of possible new water contaminants is endless, since new chemicals are issued much faster than regulators can test them.
Traditionally, ANSI/NSF certification has been divided into two categories: the contaminants with known adverse health effects, like arsenic or lead, and items which affect the taste and color of water, which are aesthetic issues not known to affect health.
Emerging contaminants are a new category of water quality concerns for which evidence of health effects has not yet been established due in part to the trace levels at which these compounds are currently being detected.
The newer chemicals that are being listed by regulatory agencies are seen below in the Emerging Contaminants list being tested to a new NSF standard called American National Standard NSF/ANSI 401. You’ll see some familiar names in the list. Yes, DEET is the stuff you spray on your body to discourage mosquitos, Ibuprofen is what you take for a headache, and Bisphenol A (aka BPA) is the ingredient in plastic bottles you’ve been trying to avoid.
Note that the allowable amount for all of these is expressed not in parts per million, or parts per billion, but in ng/L, nanograms per liter. One nanogram per liter is one one-millionth of one milligram per liter. Expressed differently, one nanogram per liter is the equivalent of one part per million of one part per million of the whole. When you think of it as slicing a pie into a million pieces then one of the pieces into a million pieces, that isn’t much.
To understand how NSF testing is done, what the chart tells you is that if they take a solution containing more or less 200 ng/L of the angina and blood pressure medicine Atenolol and put it through a filtration device, the device must reduce the Atenolol content to 30 ng/L or less to receive NSF certification.
It is noteworthy that the fairly short list of devices that have attained NSF certification for removal of Emerging Contaminants includes only carbon filtration devices, and some of these are small devices like refrigerator filters or pitcher filters. In other words, even pretty tiny carbon filters do a good job with "emerging contaminants," so if you drink water from a good carbon-based drinking water filter, or a reverse osmosis unit, you can safely stop worrying about being overcome by the page-long list of health problems associated with the anti-seizure drug Carbamazepine.
| Substance | Average influent challenge ng/L* | Maximum effluent concentration ng/L* |
| Meprobamate |
400 ± 20% |
60 |
| Phenytoin |
200 ± 20% |
30 |
| Atenolol |
200 ± 20% |
30 |
| Carbamazepine |
1,400 ± 20% |
200 |
| TCEP |
5,000 ± 20% |
700 |
| TCPP |
5,000 ± 20% |
700 |
| DEET |
1,400 ± 20% |
200 |
| Metolachlor |
1,400 ± 20% |
200 |
| Trimethoprim |
140 ± 20% |
20 |
| Ibuprofen |
400 ± 20% |
60 |
| Naproxen |
140 ± 20% |
20 |
| Estrone |
140 ± 20% |
20 |
| Bisphenol A |
2,000 ± 20% |
300 |
| Linuron |
140 ± 20% |
20 |
| Nonyl phenol |
1,400 ± 20% |
200 |
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How to Pick the Best Filter Cartridge
The “best” water filter cartridge is not necessarily the one that removes most contaminants or the one that treats the most gallons of water or the one that has the least pressure drop. The best for you is the one that does what is needed in your application.
This article makes some generalizations about water filter cartridges to help clarify what performance information provided by manufacturers means to the filter customer. We’re using “whole house” carbon filter cartridges, 4.5″ X 20″, treating chlorine and chloramine, to illustrate, but the principles apply as well to other filters, like sediment filters and “media” cartridges that are intended for problems like iron, hardness, lead, and nitrate reduction.
In general terms, the more tightly the filter media is packed together, the more effective the filter is at removing contaminants, but the more it restricts the flow of water through it and the more likely it is to become clogged by particles. The looser the media is packed, the less effective the filter is at contaminant removal, but the less it restricts the flow of water and the less likely it is to be clogged. Tighter means more effective performance but greater pressure loss and sometimes shorter life because of premature clogging.
Another generalization that’s true of most cartridges is that the slower the water goes through the filter, the more effectively it treats contaminants, the longer it lasts, and the less water pressure is lost. Conversely, the faster the flow, the poorer the performance, the greater the pressure loss, and the shorter the lifespan of the filter.
The art of selecting a filter, then, is to choose one that’s tight enough to be effective but not so tight that it restricts service flow or stops up easily. It must also be large enough to accommodate the needed service flow rate. Sometimes with cartridge filters, to get a "larger" filter the most practical approach is to install 2 or more filters in parallel. (See the picture below.)
To see how pressure drop, capacity, and micron size are related, here is a comparison of chlorine treatment figures for two 4.5″ X 20″ MatriKX carbon blocks, identical except in tightness. (Micron size is the way filter makers state tightness: the lower the micron number, the tighter the filter.)
Two Identical Carbon Block Filters of Different Micron Ratings: Chlorine Reduction
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MatriKX CTO |
MatriKX CTO+ |
| Filter Type |
Coconut Shell Carbon Block |
Coconut Shell Carbon Block |
| Micron Rating |
Nominal 5 microns |
Nominal 1 micron |
| Chlorine Removal Capacity |
34,000 gallons @ 7 gpm |
160,000 gallons @ 7 gpm |
| Pressure Drop |
8 psi @ 7 gpm |
16 psi @ 7 gpm |
| Current Retail Price |
$68.00 |
$89.00 |
Considerations
The very tight CTO+ would seem like the better value in terms of gallons treated per cost, but it is very unlikely that in residential use such a tight filter would treat 160,000 before it stops up. Also, the excessive pressure drop gets even worse as the filter picks up particulate. Its performance is remarkable, but it probably is not the better choice for whole house residential treatment of chlorine.
The looser CTO has half the pressure drop. Most residential water use is at a rate below 7 gpm, so you can expect the 34K chlorine capacity of the CTO to go up. We’ve found the CTO to be an excellent residential filter for water treated with chlorine. The CTO+ is a great choice for applications where pressure drop is not an issue and where sufficient pretreatment can be furnished to prevent premature clogging.
Granual Radial Flow Carbon Filters
The pair of filters compared below are identical “radial flow” granular filters. Though both are rated at 25 microns, the chloramine filter evidently uses a finer carbon and is therefore a bit more restrictive. These are very high grade radial flow cartridges, not to be confused with the standard axial flow granular carbon cartridges that normally use regular mesh (not powdered) carbon and have much lower performance numbers. ( Axial vs. radial explained.)
Similar Radial Flow Granular Carbon Filters: One for Chlorine, the other for Chloramine
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Pentek RFC20BB—Chlorine Grade |
Pentek CRFC20BB –Chloramine Grade |
| Filter Type |
Radial Flow GAC (powdered) |
Radial Flow Catalytic GAC (powder) |
| Micron Rating |
25 Microns |
25 Microns |
| Chlorine Removal Capacity |
70,000 gallons @ 4 gpm |
Not given, but considerably lower than the chlorine capacity. |
| Chloramine Removal Capacity |
Not given, but considerably more than the chloramine capacity. |
10,000 gallons @ 5 gpm
25,000 gallons @ 2.5 gpm
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| Pressure Drop |
0.9 psi @ 4 gpm
2 psi@ 7 gpm
4 psi @ 11 gpm
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1 psi @ 2.5 gpm
2.5 psi @ 5 gpm
5 psi @ 7 gpm
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| Current Retail Price |
$95.00 |
$168.00 |
Considerations
Note that reducing the flow rate more than doubles the lifespan of the chloramine cartridge. While this ratio doesn’t apply everywhere, as a general rule cutting the flow rate through the filter significantly adds to its life expectancy, adds to its efficiency, and reduces pressure drop. Therefore, running two filters in parallel more than doubles the valve of a single filter. In many cases using multiple filters actually costs less than using one, plus you get significantly lower pressure drop.
Split installation: each filter gets half the flow rate. Efficiency goes up, pressure drop goes down, and cost per gallon treated goes down.
With a flow rate of 5 gpm, one filter treats 10,000 gallons with a pressure drop of 2.5 psi, but two filters treat 50,000 gallons with a pressure drop of 1 psi. What’s more, operation cost is 1.6 cents per gallon for one filter and 0.66 cents for two.
Flow rate matters!
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Places to visit for additional information:
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Thanks for reading and be sure to check out the next Occasional!
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