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Mark357

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  1. A few more questions about your setup: 1) Is there an auxiliary pump that just pumps the water through the heater? It seems like it would be necessary for the mixing valve to work properly. 2) What is the total water flow rate through the heater? 3) What is the mix ratio? How much water in gpm comes from the pool system and how much is recirculated 160 F water from the heater outlet?? 4) You say that you have 6 filters. What is the design flow rate of each filter?
  2. The leak is almost definitely due to a leaking hydrostat. A hydrostat is a check valve that is installed in the bottom of the main drain. If you vacuumed directly over the main drain grate the suction could have caused the check valve to open and get stuck open. Usually all you need to do is to dive down, remove the grate and reset the valve. Sometimes you need to replace the valve if it is bad. You should go to the pool store and ask to see a hydrostat so that you know what one looks like before diving down. A hydrostat is installed as a safety device to prevent the pool from floating out of the ground when it is drained. If the water table is high enough, while the pool is drained, it can actually cause the pool to float like a boat. You should have a replacement main drain grate and hydrostat before diving so that they can be replaced if necessary.
  3. I don't see any reason that the pool builder can't proceed with a Vinyl liner. All that needs to be done is to put in a few well points and some gravel around the area to keep it dry until the pool is full. Once the pool is full, the water in the pool will have enough pressure to hold everything in place. The pool builder should have known the water table and not have been surprised by hitting water. It almost seems to me that the builder did this deliberately to get you involved and then force you to upgrade to the more expensive Gunite pool. Seems like a shady trick to me. How much more will the Gunite cost than the Vinyl liner.?
  4. It is also important to note that the salt should not have been added for the first 30 days. The salt can damage the fresh plaster. You should check the salt cell for scaling as it is almost definitely scaled. I would like to give special recognition and thanks to Richard, aka Chem Geek, for all of the help he has given to so many people. He is a super-smart and really good person.
  5. You note that this is a new pool. As new plaster is curing it gives off Calcium Hydroxide which combines with the Carbonates and Bicarbonates (Alkalinity) in the water to form Calcium carbonate (Scale) and Hydroxide ions (pH increaser). As shown here: Ca(OH)2 + CO3-- <-> CaCO3 + 2OH- Calcium hydroxide + carbonate <-> Calcium Carbonate + hydroxide. Or Calcium hydroxide + bicarbonate <-> Calcium Carbonate + water + hydroxide. Ca(OH)2 + HCO3- <-> CaCO3 + H2O + OH- If the water is not kept low in pH, Alkalinity and Calcium during the first 15 days scale will get on everything. If the SI is high during the plaster curing phase the high levels of calcium carbonate will act like a precipitating agent to force supersaturated Calcium Carbonate out of the water. My calculations for the SI are +0.54 and + 0.70 using two different methods. It is important to stay between 0.0 and 0.20 for the first 3 months. After the first three months the range is 0.0 to 0.3. You can add a "Stain and Scale" control chemical to help. The aeration caused by the fountain and the aeration caused by the salt cell cause some of the carbon dioxide to be outgassed. Carbon Dioxide is lost as it goes over the fountain this immediately causes three effects: 1) The pH is increased. This lowers the solubility of Calcium Carbonate and the equilibrium between carbonate and bicarbonate shifts towards carbonate. 2) The increase in the carbonate concentration due to the pH increase creates more calcium carbonate. 3) The solubility of Calcium Carbonate is proportional to the level of dissolved Carbon Dioxide in the water. As the carbon dioxide level drops, the water can hold less calcium carbonate and the Calcium Carbonate precipitates out of solution creating scale. The same thing happens in a salt cell due to the effects of the aeration causing the loss of carbon dioxide and the reduction of hydrogen at the cathode given by this equation here: 2H2O + 2e- --> H2 (g) + 2OH- which creates hydroxide ions which raises the pH even further. The other challenge that you are dealing with is the warm water temperature at 92 F. When calcium is dissolved in water heat is given off (exothermic), therefore its solubility is inversely proportional to temperature. Also, Carbon Dioxide is less soluble in hot water. At 92 degrees F water can only hold about 90% of the dissolved Carbon Dioxide as water at 84 degrees F. And, as water is heated, the equilibrium between bicarbonate ions and carbonate ions is shifted toward carbonate. There is not much you can do about the temperature of the water. I would recommend that you avoid using any chemicals that contain Calcium, like Calcium Hypochlorite. Try to get the Calcium below 270. Reference(s) (General) http://www.advancedaquarist.com/issues/mar2002/chem.htm
  6. The OP noted: "The Heater Rep recommends 130 minimum inlet temp to prevent condensation on the outside of the heat exchanger." Condensation can be a concern if there is high humidity and the hot air is contacting a cold heat exchanger. 130 degrees F is unnecessary. I think that the scaling can be attributed to these primary factors: 1) Excessive water temperatures in the heat exchanger. (See notes) 2) High SI at the time of scaling. Estimate of +0.4 in pool and +1.0 in the heat exchanger. 3) High Total Dissolved Solids in excess of 1,000 for a non-salt pool. High levels of TDS can cause corrosion and scaling even though high TDS will also increase the solubility of the calcium. 4) Large amounts of concrete dust from saw cutting getting into the system. 5) Large amounts of Plaster dust getting into the circulation system. Recommendations: 1) Limit water temperature to less than 120 F in the heat exchanger. 2) Maintain a Saturation Index between 0.0 and 0.2 3) Reduce Total Dissolved Solids (Excluding Salt) to less than 1,000. 3) Vacuum to waste whenever heavy dust or debris needs to be vacuumed. 4) Add DE filtration to the system to remove finer particles than the sand filters can remove. 5) Add a "Stain and Scale" control chemical. 6) Maintain Calcium below 240 ppm. Note: When calcium is dissolved in water heat is given off (exothermic), therefore its solubility is inversely proportional to temperature. In addition to the high temperature in the heat exchanger causing a direct solubility effect on the Calcium Carbonate, the high temperature also has three indirect effects. (1)Carbon dioxide is less soluble in hot water; therefore it comes out of solution at 160 F in the heat exchanger. Example: At 140 F the water can only hold 44% of the carbon dioxide level that it can at 85 F. Or water at 85 F can hold 2.24 times as much dissolved carbon dioxide as water at 140 F. This raises the pH in the exchanger, which lowers the solubility of the calcium carbonate. (2) As the pH is raised, the equilibrium between carbonate and bicarbonate shifts towards carbonate. [1] The increased level of carbonate combines with the calcium to form calcium carbonate. The reduction of the bicarbonate shifts the equilibrium of calcium bicarbonate with Calcium carbonate and carbon dioxide towards the calcium carbonate. CaCO3 + CO2 + H2O <-> Ca(HCO3)2 (3) The solubility of calcium carbonate is proportional to the level of dissolved Carbon Dioxide in the water. As the carbon dioxide level drops, the water can hold less calcium carbonate. (4) As water is heated, the equilibrium between bicarbonate ions and carbonate ions is shifted toward carbonate. Water at 176 F will have 2.4 times the carbonate concentration as it will at 77 F. [1] The increased level of carbonate combines with the calcium to form calcium carbonate. The reduction of the bicarbonate shifts the equilibrium of calcium bicarbonate with Calcium carbonate and carbon dioxide towards the calcium carbonate. CaCO3 + CO2 + H2O <-> Ca(HCO3)2 [1] http://www.advancedaquarist.com/issues/mar2002/chem.htm
  7. Richard, I think that the heat exchanger is a set of finned copper tubes that pass over the natural gas fire in the heater. The pool water goes through the tubes and the heat from the fire heats the air in the heater; the air then passes over the heat exchanger and out of the heater. The OP meant that the water going into the heat exchanger was 130 F and it was coming out at 167 F. The temperature of the air that contacts the heat exchanger is probably well over 500 F. I think that the OP's use of the term "forced air" caused some confusion. I think that he meant that the heater had a fan on the exhaust that creates air movement through the heater rather than relying on just the air flow caused by hot air rising. This is becoming a standard on most new heaters. Most likely the SI was very positive in the heat exchanger. The OP is considering switching to a dual heat exchange process that uses two heat exchangers. The first one will be in the heater and the second will then exchange heat with the water in a second exchanger. Calcium is a component of TDS. If you increase calcium, you increase TDS. Calcium is a component of TDS that increases the SI. Carbonates and Bicarbonates are a component of TDS, they also increase the SI. In this case the TDS is almost definitely not salt. Most likely the primary components of the TDS are Tricalcium silicate and Dicalcium silicate, which form Calcium silicate hydrate + Calcium hydroxide; and Tricalcium aluminate (forms calcium aluminate hydrate), Tetracalcium aluminoferrite and Gypsum. All of these will contribute to the total level of dissolved solids that the water can hold. Most likely the OP only recently switched to a negative SI after the heaters scaled again. He does not say that they have scaled after switching to a negative SI. Another issue with high TDS is the increased conductivity of the water. If there is any type of stray current going through the water and the heat exchanger is acting like a negatively charged anode it will attract positively charged cations, like calcium, like what happens in a salt cell. If the heat exchanger is acting like a positively charged anode it will be corroded at an accelerated rate. Using your model it seems like you can just continue to add dissolved solids indefinitely. At some point the water becomes saturated and can not hold any more. Mark.
  8. Richard, There are several problems that are contributing to the scaling. The first is the extremely high water temperatures in the heat exchangers. It seems that they were going as high as 160 to 170 degrees. That makes the current SI +0.2 to +0.3. Normally, water temperatures in a heat exchanger are much lower. Most likely the pH has been well over 7.1 many times, which increases it even further. The OP began going negative SI after finding scaling and as an attempt to control it. At a pH of 7.7 the SI in the exchanger will be 0.8 to 0.9. The OP notes that the pool was recently built. New plaster gives off lots of calcium carbonate and hydroxides. The O.P's pool is on the order of 115 ft X 115 ft. That is a lot of plaster, which would have generated a lot of dust. It is also likely that the alkalinity has been higher in the past. The next issue is the high TDS at "TDS 2300", which I believe are from all of the concrete sawing and construction that the OP mentioned. Concrete that is cut with a diamond blade saw is a very fine powder. It can cause many scaling issues. It is a very bad thing to get into your pool and into your filtration system. The 2300 level is the current level; it was probably much higher earlier while all of the construction work was being done. Concrete being cut generates a lot of dust which gets into the filtration system and causes the TDS to spike to very high levels. I think that the OP needs to get these levels to below 1000. You are also subtracting the TDS value from the SI equation. The make-up of the TDS and what effect you're calculating determines whether it is subtracted or added. In this case, I think it should be added. If you add the TDS, you get closer to + 0.4 to +0.5. Add on 0.6 for the times that the pH was at 7.7 and you get +1.0 to + 1.1. We need to know the saturation index of each component of the TDS and the Index of the combined components. Scale can be many other things than just calcium carbonate. Add all of these factors together and you are going to have major problems. Note: I take care of concrete pools with heat exchangers where I run an average range of 0.0 to 0.25 positive SI with no scaling problems. Also, without actually visiting the job site it is difficult to know what other factors are relevant that the operator might not know to include in their description.
  9. Here are a few more notes related to your situation: I noticed that you mentioned "saw cutting concrete around the pool for two weeks". Concrete dust is one of the worst things you can get into your system. When the dust went through the system it reached high concentrations. If the dust was vacuumed through the system it reached super high levels. If the heater was running while the levels were high that would cause scaling. The dust should have been vacuumed to waste, and not through the filter. If it was vacuumed through the system that would explain the cloudiness. I would imagine that your flow rate is probably in the 700 to 900 gpm range with a 15 to 20 HP pump and a correspondingly sized sand filter. 1) What are the specs on your system and equipment? Pump, filter, flow rate etc? Here are a few more things you can do: 1) Get an extra 3/4 or 1.0 HP pump and use it to vacuum to waste instead of using the filtration system to vacuum. This will avoid getting so much dust and junk in your system. It will also reduce your TDS as it will remove about 1 inch of pool water per vacuum. 2) Add a 120 GPM DE filter to the output of the sand filter to get more of the finer particles out of the water. You can set it up with a few 2 inch Jandy "never-lube" valves so that it is easy to use. You would divert about 100 GPM from the output of the sand filter and through the DE filter using a flow meter to set the correct flow. By using the existing flow rate there is no extra pump to buy or install. By using sand filtered water you will get a very long operational time out of the DE. This is not a common thing to do, so don't expect anyone to immediately understand what you want, or why you're doing it.
  10. Richard, I do not have data related to equilibrium constants. I would suppose that since the DMH does not do a lot to protect the bromine from the sunlight the C5H6BrClN2O2 is probably not a very significant percentage. I would imagine that the HOCl + HOBr + C5H8N2O2 would be the dominant species. It seems that the C5H8N2O2 would probably build up like cyanuric acid. Possibly if the levels were high enough (perhaps over 100 ppm) it would begin to interfere with the chlorine or bromine. I think that as long as the level was low enough it should not cause much trouble. As far as the bromide ions, I am not sure how long they take to break down. I'm not sure what the breakdown mechanism would be. Of course dilution would play a part, but that takes a long time. What are the equilibrium constants related to chlorine and CYA?
  11. Here is the formula for Trichloroisocyanuric acid………………..(C3Cl3N3O3) Active Chlorine 45.76% by mass C3Cl3N3O3 + 3H2O <-> 3HOCl + C3H3N3O3 Every pound of Trichloroisocyanuric acid (C3Cl3N3O3) contains 0.4576 lb of chlorine and the rest is 0.5424 pounds of cyanuric acid. A 35 lb. bucket of trichlor contains 18.98 lbs of cyanuric acid. That will raise the cyanuric by 110 ppm in 20,000 gallons. How much trichlor have you used in the 6 weeks?
  12. Here is the formula for Dimethylhydantoin…C5H8N2O2 Here is the formula for Cyanuric acid…….....C3H3N3O3 As you can see they are very similar. C3H3N3O3 + HOCl <-> H2O + C3H2ClN3O3 Cyanuric acid combines with hypochlorous acid to form a chlorinated isocyanurate. As the hypochlorous acid gets used up the equilibrium shifts and some of the chlorinated isocyanurate becomes hypochlorous acid. Here is the formula for Trichloroisocyanuric acid………………..(C3Cl3N3O3) Active Chlorine 45.76% by mass C3Cl3N3O3 + 3H2O <-> 3HOCl + C3H3N3O3 Every pound of Trichloroisocyanuric acid (C3Cl3N3O3) contains 0.4576 lb of chlorine and the rest is 0.5424 pounds of cyanuric acid. A 35 lb. bucket of trichlor contains 18.98 lbs of cyanuric acid. That will raise the cyanuric by 110 ppm in 20,000 gallons. Here is the formula for 1-bromo-3-chloro-5,5-dimethyl hydantoin…(C5H6BrClN2O2) Active Bromine 33.09% by mass Active Chlorine 14.68% by mass You are getting the same number of chlorine atoms and bromine atoms; bromine is just 2.28 times as heavy as chlorine. As you can see, the bromine tabs come with chlorine already mixed in, so the chlorine has to be somewhat compatible with the bromine and the dimethylhydantoin. C5H6BrClN2O2 + 2H2O <-> HOCl + HOBr + C5H8N2O2 This shows that the dimethylhydantoin can build up quite quickly. As in the trichlor tabs, as significant portion of the mass of the product is the carrier. There is also C5H6Cl2N2O2 (Dichlorodimethylhydantoin) and C5H6 Br 2N2O2 (Dibromodimethylhydantoin) C5H6Br2N2O2 + 2H2O <-> 2HOBr + C5H8N2O2 The dimethylhydantoin acts in a similar way to the cyanuric acid although it is not nearly as effective. It is primarily a carrier for the bromine. I think that it's important to minimize the buildup of the dimethylhydantoin. As the hypobromous acid oxidizes something it becomes a bromide ion and it remains in the water until it is reenergized into hypobromous acid. Chlorine is a good activator of bromide ions. If the dimethylhydantoin or the bromide ion levels are too high, sometimes it's best to drain and refill. Most of the time it is not necessary to drain and refill.
  13. 30/X = Life of plaster. X = 10^Y + 2.4Y. Y = SI below 0.0. X= 10^0.0 + 2.4 x 0.0 = 1.00. Life of plaster = 30/1.00 = 30.0 years. X= 10^0.1 + 2.4 x 0.1 = 1.50. Life of plaster = 30/1.50 = 20.0 years. As you can see just going 0.1 negative cause a 10 year reduction in plaster expected life. This is my formula based on my experience and my opinion. I believe that it is a fairly accurate formula assuming everything else is done right. Most people will tell you that 15 years is good for plaster. Under ideal conditions plaster can last for 30 years. Water that is saturated with calcium carbonate will not dissolve very much plaster. It will still dissolve some due to various factors. This is also based on my opinion of what a good plaster finish is vs. what is a poor plaster finish. It is also important to avoid scaling. Therefore, you should also avoid going too high on the SI. Usually less than 0.3 is best.
  14. Using a dual heat exchanger will be less efficient, but it may be a good solution if there is not too much loss of efficiency. Did the pool tech from Spear corp. indicate how much efficiency would be lost with the dual heat exchanger setup?
  15. The stains can happen when your pH or alkalinity are low and the granular shock hits the plaster.. What were your pH and alkalinity at the time you shocked?
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