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#1
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Well pump pressure tank...
On Sep 17, 5:38*pm, "Dimitrios Paskoudniakis"
wrote: "Paul Franklin" wrote in message ... On Thu, 17 Sep 2009 19:20:23 -0400, Tony wrote: My bladder type water tank is rated 20 gallons. With no water I have 26.5 lbs of air pressure in tank. The pump cuts in at about 28lbs. and out at about 51lbs. With the tank full I only get 6.75 gallons of water before the pump runs again. *Is this right? *If not, what's wrong? Thanks If you check pressure tank spec sheets, they will specify the "Draw Down" rating for the different size tanks and pressure switch settings. *Draw down is the amount of water you will get between cut-out and cut-in pressures. A quick check of a brand or two on the web shows 20 gal tanks are rated for about 6 gallons of draw down when using 30-50 settings. So what you are seeing is about right for that tank with those settings. Switching to a larger tank will prevent the pump from cycling as often, but you have to balance the capacity of your well and the run time of the pump. *A larger tank means the pump runs longer (although less often). *This can cause the water level in the well to fall below the pump (low capacity well), and in extreme cases longer run time can cause the pump to overheat. Many of the tank and pump web sites have guidlines for sizing the tank properly, but you need to know some details about your pump and well. As tanks go, 20 gallons is pretty small. HTH, Paul F. Get rid of the tank and go with a Grundfos variable speed pump and control system. *It pressurizes in a small two-gallon tank while it pumps and only operates on demand. *Variable speed means constant pressure. *If you set it to 70 psi, turn on the washing machine, flush a toilet at the same time the shower is on, the shower pressure is unaffected. *Try that with a pressure tank. *I switched last year and I'm very happy.- Hide quoted text - - Show quoted text - Yes, but the drawback is sthat the pump runs _every_ time water is drawn. It is the start cycle that is hardest on pumps. Harry K |
#2
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Well pump pressure tank...
On Sep 17, 11:24*pm, harry k wrote:
On Sep 17, 5:38*pm, "Dimitrios Paskoudniakis" wrote: "Paul Franklin" wrote in message .. . On Thu, 17 Sep 2009 19:20:23 -0400, Tony wrote: My bladder type water tank is rated 20 gallons. With no water I have 26.5 lbs of air pressure in tank. The pump cuts in at about 28lbs. and out at about 51lbs. With the tank full I only get 6.75 gallons of water before the pump runs again. *Is this right? *If not, what's wrong? Thanks If you check pressure tank spec sheets, they will specify the "Draw Down" rating for the different size tanks and pressure switch settings. *Draw down is the amount of water you will get between cut-out and cut-in pressures. A quick check of a brand or two on the web shows 20 gal tanks are rated for about 6 gallons of draw down when using 30-50 settings. So what you are seeing is about right for that tank with those settings. Switching to a larger tank will prevent the pump from cycling as often, but you have to balance the capacity of your well and the run time of the pump. *A larger tank means the pump runs longer (although less often). *This can cause the water level in the well to fall below the pump (low capacity well), and in extreme cases longer run time can cause the pump to overheat. Many of the tank and pump web sites have guidlines for sizing the tank properly, but you need to know some details about your pump and well. As tanks go, 20 gallons is pretty small. HTH, Paul F. Get rid of the tank and go with a Grundfos variable speed pump and control system. *It pressurizes in a small two-gallon tank while it pumps and only operates on demand. *Variable speed means constant pressure. *If you set it to 70 psi, turn on the washing machine, flush a toilet at the same time the shower is on, the shower pressure is unaffected. *Try that with a pressure tank. *I switched last year and I'm very happy.- Hide quoted text - - Show quoted text - Yes, but the drawback is sthat the pump runs _every_ time water is drawn. *It is the start cycle that is hardest on pumps. Harry K Besides a variable speed pump, the other and more common way to achieve constant pressure is with the use of a cycle stop valve which works in conjunction with a small tank like the OP's 20 gal one. Essentially it's a special valve goes between the pump and the rest of the system and it maintains a constant pressure within a wide range of flow rates. Say it is set to 50PSI. Then it works by throttling back what the pump can deliver so the pressure is 50PSI whether you are getting 2GPM or 12GPM. It will only allow a pressure higher than the set 50PSI at flow rates BEKOW 1GPM. That is done to allow it to then fill the tank up to whatever the cuttoff pressure is, which might be 70PSI. Which is better is a subject of debate among the manufacturers of the two approaches. One thing is for sure, the cycle stop valve can be used with a regular pump. A variable speed pump is a special pump with more complexity, cost and controls required. The operation of the OP;s tank sounds about right. The guidelines for those kind of tanks generally call for the tank bladder to be pressurized when empty and drained to 2PSI below whatever the cut-in pressure is for the pump. So with a cut-in of 28, the tank should be around 26. His is 26.5. |
#3
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Well pump pressure tank...
On Sep 18, 5:22*am, wrote:
On Sep 17, 11:24*pm, harry k wrote: On Sep 17, 5:38*pm, "Dimitrios Paskoudniakis" wrote: "Paul Franklin" wrote in message .. . On Thu, 17 Sep 2009 19:20:23 -0400, Tony wrote: My bladder type water tank is rated 20 gallons. With no water I have 26.5 lbs of air pressure in tank. The pump cuts in at about 28lbs. and out at about 51lbs. With the tank full I only get 6.75 gallons of water before the pump runs again. *Is this right? *If not, what's wrong? Thanks If you check pressure tank spec sheets, they will specify the "Draw Down" rating for the different size tanks and pressure switch settings. *Draw down is the amount of water you will get between cut-out and cut-in pressures. A quick check of a brand or two on the web shows 20 gal tanks are rated for about 6 gallons of draw down when using 30-50 settings. So what you are seeing is about right for that tank with those settings. Switching to a larger tank will prevent the pump from cycling as often, but you have to balance the capacity of your well and the run time of the pump. *A larger tank means the pump runs longer (although less often). *This can cause the water level in the well to fall below the pump (low capacity well), and in extreme cases longer run time can cause the pump to overheat. Many of the tank and pump web sites have guidlines for sizing the tank properly, but you need to know some details about your pump and well. As tanks go, 20 gallons is pretty small. HTH, Paul F. Get rid of the tank and go with a Grundfos variable speed pump and control system. *It pressurizes in a small two-gallon tank while it pumps and only operates on demand. *Variable speed means constant pressure. *If you set it to 70 psi, turn on the washing machine, flush a toilet at the same time the shower is on, the shower pressure is unaffected. *Try that with a pressure tank. *I switched last year and I'm very happy.- Hide quoted text - - Show quoted text - Yes, but the drawback is sthat the pump runs _every_ time water is drawn. *It is the start cycle that is hardest on pumps. Harry K Besides a variable speed pump, the other and more common way to achieve constant pressure is with the use of a cycle stop valve which works in conjunction with a small tank like the OP's 20 gal one. Essentially it's a special valve goes between the pump and the rest of the system and it maintains a constant pressure within a wide range of flow rates. *Say it is set to 50PSI. * Then it works by throttling back what the pump can deliver so the pressure is 50PSI whether you are getting 2GPM or 12GPM. * *It will only allow a pressure higher than the set 50PSI at flow rates BEKOW 1GPM. *That is done to allow it to then fill the tank up to whatever the cuttoff pressure *is, which might be 70PSI. Which is better is a subject of debate among the manufacturers of the two approaches. * One thing is for sure, the cycle stop valve can be used with a regular pump. *A variable speed pump is a special pump with more complexity, cost and controls required. The operation of the OP;s tank sounds about right. * *The guidelines for those kind of tanks generally call for the tank bladder to be pressurized when empty and drained to 2PSI below whatever the cut-in pressure is for the pump. * *So with a cut-in of 28, the tank should be around 26. * His is 26.5.- Hide quoted text - - Show quoted text - Yes, his system is operating correctly. Oddly, although the standard is 2psi below cut-in, some tanks (and mine included) say 'same as cut- in'. I cannot understand why the pump would ever start with pre- charge at or higher than cut-in. I set mine to 2 psi below. Harry K |
#4
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Well pump pressure tank...
On Sep 18, 11:52*am, wrote:
On Fri, 18 Sep 2009 07:33:31 -0700 (PDT), harry k wrote: Yes, his system is operating correctly. *Oddly, although the standard is 2psi below cut-in, some tanks (and mine included) say 'same as cut- in'. *I cannot understand why the pump would ever start with pre- charge at or higher than cut-in. *I set mine to 2 psi below. The tank pressure only shows up at the pump switch when there is some water in the bladder to transfer it. The pressure drops to zero on the water side when the bladder is empty. And even if there is some water in it, say a couple gallons, the pressure is going to be lower than the pressure in the bladder. The pressure difference is made up by the tension on the bladder as it stretches. As you pointed out, with an empty tank the gauge will read zero. As you start to pump water into it, the water pressure will gradually rise. It's not going to be instantly equal to the pressure that is pre-loaded into the bladder. |
#5
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Well pump pressure tank...
On Sep 18, 3:29*pm, wrote:
On Sep 18, 11:52*am, wrote: On Fri, 18 Sep 2009 07:33:31 -0700 (PDT), harry k wrote: Yes, his system is operating correctly. *Oddly, although the standard is 2psi below cut-in, some tanks (and mine included) say 'same as cut- in'. *I cannot understand why the pump would ever start with pre- charge at or higher than cut-in. *I set mine to 2 psi below. The tank pressure only shows up at the pump switch when there is some water in the bladder to transfer it. The pressure drops to zero on the water side when the bladder is empty. And even if there is some water in it, say a couple gallons, the pressure is going to be lower than the pressure in the bladder. * The pressure difference is made up by the tension on the bladder as it stretches. * *As you pointed out, with an empty tank the gauge will read zero. * As you start to pump water into it, the water pressure will gradually rise. *It's not going to be instantly equal to the pressure that is pre-loaded into the bladder. 1. The bladder 'tension' will not approach cut-off psi. Pressure in both sides will be, for practical purposes, identical. Not sure but I believe the bladder is flacid when the tank is empty (fastened at the bottom, not top). Some of them are replacable without dissembling the tank. 2. The gauge will never reach zero if there is a little bit of water in it. 3. The reason the pressure drops to zero (I overlooked that) is that the bladder blocks the tank exit. Harry K |
#6
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Well pump pressure tank...
harry k wrote:
Yes, his system is operating correctly. Oddly, although the standard is 2psi below cut-in, some tanks (and mine included) say 'same as cut- in'. I cannot understand why the pump would ever start with pre- charge at or higher than cut-in. I set mine to 2 psi below. It will work with it charged higher than cut in because once the tank is empty the bladder has no more room to move so the pressure coming out of the tank goes to zero even if the bladder has pressure. I'll try changing mine to about .5 psi below cut in. I would think going to the same or higher pressure than cut in would give the system a sort of water hammer type problem when the water stops, or almost stops, then the pump kicks in. |
#7
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Well pump pressure tank...
"harry k" wrote in message ... On Sep 17, 5:38 pm, "Dimitrios Paskoudniakis" wrote: "Paul Franklin" wrote in message ... On Thu, 17 Sep 2009 19:20:23 -0400, Tony wrote: My bladder type water tank is rated 20 gallons. With no water I have 26.5 lbs of air pressure in tank. The pump cuts in at about 28lbs. and out at about 51lbs. With the tank full I only get 6.75 gallons of water before the pump runs again. Is this right? If not, what's wrong? Thanks If you check pressure tank spec sheets, they will specify the "Draw Down" rating for the different size tanks and pressure switch settings. Draw down is the amount of water you will get between cut-out and cut-in pressures. A quick check of a brand or two on the web shows 20 gal tanks are rated for about 6 gallons of draw down when using 30-50 settings. So what you are seeing is about right for that tank with those settings. Switching to a larger tank will prevent the pump from cycling as often, but you have to balance the capacity of your well and the run time of the pump. A larger tank means the pump runs longer (although less often). This can cause the water level in the well to fall below the pump (low capacity well), and in extreme cases longer run time can cause the pump to overheat. Many of the tank and pump web sites have guidlines for sizing the tank properly, but you need to know some details about your pump and well. As tanks go, 20 gallons is pretty small. HTH, Paul F. Get rid of the tank and go with a Grundfos variable speed pump and control system. It pressurizes in a small two-gallon tank while it pumps and only operates on demand. Variable speed means constant pressure. If you set it to 70 psi, turn on the washing machine, flush a toilet at the same time the shower is on, the shower pressure is unaffected. Try that with a pressure tank. I switched last year and I'm very happy.- Hide quoted text - - Show quoted text - Yes, but the drawback is sthat the pump runs _every_ time water is drawn. It is the start cycle that is hardest on pumps. Harry K _______________________________________ The start cycle is a gradual spinup, not a sudden max speed, so incorrect there. As for pump runs when water is on demand, so what? Ahhhhh, 70 psi. |
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