Descaling still necessary if using pre-filter water? - Page 2
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LaDan
- Posts: 963
- Joined: 13 years ago
Paul,
I am not sure what he tested, if it was TDS or the water hardness.
Recommended TDS for coffee is around 120-130 ppm or mg/liter (Total Dissolved Solids) - these are solids smaller than a size of 2 microns.
Recommended water hardness for espresso is around 70-80 mg per liter.
The water in NYC are way below these values.
Hardness (for scaling risks) are from dissolved calcium and magnesium. At 70 mg/L you are at no risk. The risk is from the calcium.
Keep in mind that boiler temperature also plays a role in creating scale. The higher the temp the higher the possibility of scale. Note that brewing temp is lower than steaming temp. So theoretically scale can develop in a steam boiler before it develops in a brew boiler.
At 70 mg/L you are at no risk of developing scale at the brewing temp pipes and boiler.
NYC is way below 70. NYC water is considered "too soft" for espresso (although many expert will tell you that the espresso taste in the best shops in NYC is just fine). Common experience and knowledge in NYC is that at those levels scale does not accumulate in steam boilers either.
BTW, formation of scale (Calcium Carbonate) involved the values of the TDS, Hardness, PH, alkalinity and temperature. Again, the values of these factors in NYC municipal waters is such that scale normally does not form.
Bottom line, as we say around here: forgetaboutit. You've nothing to worry about.
I am not sure what he tested, if it was TDS or the water hardness.
Recommended TDS for coffee is around 120-130 ppm or mg/liter (Total Dissolved Solids) - these are solids smaller than a size of 2 microns.
Recommended water hardness for espresso is around 70-80 mg per liter.
The water in NYC are way below these values.
Hardness (for scaling risks) are from dissolved calcium and magnesium. At 70 mg/L you are at no risk. The risk is from the calcium.
Keep in mind that boiler temperature also plays a role in creating scale. The higher the temp the higher the possibility of scale. Note that brewing temp is lower than steaming temp. So theoretically scale can develop in a steam boiler before it develops in a brew boiler.
At 70 mg/L you are at no risk of developing scale at the brewing temp pipes and boiler.
NYC is way below 70. NYC water is considered "too soft" for espresso (although many expert will tell you that the espresso taste in the best shops in NYC is just fine). Common experience and knowledge in NYC is that at those levels scale does not accumulate in steam boilers either.
BTW, formation of scale (Calcium Carbonate) involved the values of the TDS, Hardness, PH, alkalinity and temperature. Again, the values of these factors in NYC municipal waters is such that scale normally does not form.
Bottom line, as we say around here: forgetaboutit. You've nothing to worry about.
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allon
- Posts: 1639
- Joined: 13 years ago
I would say that steam boilers are more likely to scale because when you release steam you leave the minerals behind, whereas when you release hot water, the minerals go with the water.
This is the first I've seen it suggested that water temp plays a role in scale formation.
Please describe the mechanism.
This is the first I've seen it suggested that water temp plays a role in scale formation.
Please describe the mechanism.
LMWDP #331
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LaDan
- Posts: 963
- Joined: 13 years ago
Check out Langelier Saturation Index (Google).
This index (LSI for short) has 3 values that will interest us with regard to scaling.
The LSI indicate the saturation level of Calcium Carbonate (CaCo3) in the water.
An LSI value of 0, the water is considered to be neutral. It will have neither scale-forming nor scale removing.
An LSI value >0 (a positive number) means that the water is "supersaturated" with respect to calcium carbonate (CaCO3) and scale forming may occur.
An LSI value < 0 (a negative number) means that the water is undersaturated with respect to CaCo3 and it will REMOVE calcium buildup (scale) from pipes and boilers.
Basically, if the water is under saturated with calcium, it can dissolve calcium from the walls of the boiler and pipes. If the water is supersaturated it will deposit CaCo3 on the pipes and boiler walls.
It is similar to the phenomenon that hard water or high TDS water will not extract coffee ideally, and too soft water or too low TDS will over extract coffee. Which is why a TDS of 120-130 is considered ideal for coffee extraction. In other words, the water has a maximum amount that it can dissolve. The more TDS it already had in it, the less coffee it can dissolve. Same with the Calcium, if it is soft water it can absorb calcium from the scaling and remove it.
Temperature affects the LSI formula. Check out this LSI calculator http://www.lenntech.com/calculators/lan ... gelier.htm it will not allow you to put temp higher than 79C. But click on table 2 and choose tap water, change TDS to 70, and then see what happens when you change temp from 20C to 79C. The LSI saturation point changes to a higher number.
Also about temperature, this is from Wiki:
This index (LSI for short) has 3 values that will interest us with regard to scaling.
The LSI indicate the saturation level of Calcium Carbonate (CaCo3) in the water.
An LSI value of 0, the water is considered to be neutral. It will have neither scale-forming nor scale removing.
An LSI value >0 (a positive number) means that the water is "supersaturated" with respect to calcium carbonate (CaCO3) and scale forming may occur.
An LSI value < 0 (a negative number) means that the water is undersaturated with respect to CaCo3 and it will REMOVE calcium buildup (scale) from pipes and boilers.
Basically, if the water is under saturated with calcium, it can dissolve calcium from the walls of the boiler and pipes. If the water is supersaturated it will deposit CaCo3 on the pipes and boiler walls.
It is similar to the phenomenon that hard water or high TDS water will not extract coffee ideally, and too soft water or too low TDS will over extract coffee. Which is why a TDS of 120-130 is considered ideal for coffee extraction. In other words, the water has a maximum amount that it can dissolve. The more TDS it already had in it, the less coffee it can dissolve. Same with the Calcium, if it is soft water it can absorb calcium from the scaling and remove it.
Temperature affects the LSI formula. Check out this LSI calculator http://www.lenntech.com/calculators/lan ... gelier.htm it will not allow you to put temp higher than 79C. But click on table 2 and choose tap water, change TDS to 70, and then see what happens when you change temp from 20C to 79C. The LSI saturation point changes to a higher number.
Also about temperature, this is from Wiki:
Google: "effect of temperature on Langelier saturation index" (couldn't post links for some reason).It is also worth noting that the LSI is temperature sensitive. The LSI becomes more positive as the water temperature increases. This has particular implications in situations where well water is used. The temperature of the water when it first exits the well is often significantly lower than the temperature inside the building served by the well or at the laboratory where the LSI measurement is made. This increase in temperature can cause scaling, especially in cases such as hot water heaters. Conversely, systems that reduce water temperature will have less scaling.
