What are total dissolved solids and where do they originate?
Dissolved solids found in water are any substances other than the pure hydrogen and oxygen elements that compose the water. These dissolved solids include minerals, salts, metals, organic waste and suspended solids such as wood pulp. The amount of total dissolved solids (TDS) present in the water can cause water to be unsafe to drink. The source of these contaminants are mostly from agricultural runoff, surface runoff or are due to the natural weathering of rocks and soils. The average TDS level of tap water is between 170-400 parts per million (ppm). TDS levels between 300-500 ppm are considered high and may contain harmful contaminants that may be hazardous if consumed.
How can you tell what level of TDS is in your water?
We offer a variety of meters that are used to measure the level of TDS in your tap water and your filtered water. These meters can be helpful in determining when will be the most accurate time to replace your filters if a filtration system is installed. Most reverse osmosis membranes have a lifespan of 2-5 years. Because this is such a vague filter lifespan, it is difficult to actually judge when it should be changed. Using a TDS meter, you can calculate the rejection rate of the reverse osmosis membrane and determine exactly when the replacement filters and the membrane should be replaced. The consumer can be reassured through the TDS meter that the filters are being replaced as soon as they are at capacity.
What is the rejection rate?
The rejection rate is calculated when the TDS level of the filtered water processed through the RO system (RO product water) is measured and is subtracted from the TDS level of the unfiltered tap water that bypasses the RO system (pre-RO feed water). That result is then divided by the pre-RO feed water and then is multiplied by 100. For example, if the TDS level of the filtered water is 25 ppm and the TDS level of the unfiltered water is 350 ppm, this is what the equation would look like:
350ppm – 25ppm = 325ppm
325ppm / 350ppm = 0.92
0.92 x 100 = 92% Rejection rate
What TDS meters do we offer?
The CT-1 meter has an L.E.D. light that indicates when the filter should be changed. When it turns red the filter has met its capacity and should be changed. This unit includes 2 AA batteries. The DM-1 is an inline filter that measure the feed water and the product water on the same unit and it has 1/4″ quick-connect inlets. The hand held TDS meters that we offer are the TDS-3 and the TDS-4. The TDS-3 has a built-in digital thermometer and a carrying case with a belt clip. The TDS-4 or the Pocket Size TDS meter is the smallest TDS meter on the market and has a 3-year limited warranty.
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Daniel says
Hello Goldie,
You need the Holmes HWF100 Humidifier filter, which fits your HM-7808 filter.
http://www.filtersfast.com/Holmes-HWF100-Humidifier-Air-Filter.asp
I called Holmes to confirm this is the correct filter and I will make the changes to our description to reflect that.
Let us know if you have any further questions. We are happy to help.
-Daniel
goldie scott says
i bought a holmes portablehumidifer i cannot find a no. 7808 filter anywhere.i will never buy another holmes again.i am not happy with your company.