Well Tank Type / Size

Discussion in 'Pumps and Tanks Well Forum & Blog' started by devans175, Jun 21, 2011.

  1. devans175

    devans175 New Member

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    I need to replace my well tank. The existing tank is a 32 gallon well x trol. I have very acidic water so I thought it would be best to replace it with a composite of fiberglass tank.

    What is the proper size tank? The existing 32 gallon one seems to do just fine, but would there be an advantage to going a little larger? My house is 2/2 baths and it's just me living there. It's unlikly that there will ever be more than 2 people. I was looking at a 30 gallon or 40 gallon Wellmate. Any thoughts?

    Note: I'm in the middle of installing an acid neutralizer and I noticed the tank and surrounding fittings are in rough shap.. starting to leak. I decided I should go ahead and replace the tank "while I'm at it"..
     
    Last edited: Jun 21, 2011
  2. LLigetfa

    LLigetfa DIYer, not in the trades

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    A tank is not sized to the number of people or the number of bathrooms. It is sized to the GPM of the pump with the intent of reducing excess cycling. Rule of tumb is that a pump should run for more than a minute, so a 10 GPM pump should have a tank with 10 gallons of drawdown. Of course you could also limit cycling with a CycleStopValve.
     
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  4. Drewmcg

    Drewmcg New Member

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    I'm no expert, but doubt that fiberglass would be an advantage, given that quality metal tanks have linings to keep the water from ever touching metal. With most of these tanks, the water is in contact only with a butyl (if a quality tank) or vinyl bladder or diaphram. Of course, if you install an acid neutralizer upstream of the tank, then acid should not be an issue in any event.

    I just finished diagnosing a storage tank problem at my house (flotec sourced Sears captive air tank). I would steer you away from a flotec model toward a higher-quality tank. The Amtrols have a seven year warranty, and should last 1.5-2 times that (or more, in your low-use application). The other brand that I read a lot of good things about was Flexon (though they seem to be harder to find).

    From my research, the proper sizing of a tank depends mostly on the flow rate of the pump. To determine this, you need two pieces of data: (i) how many seconds the pump runs from the time it kicks in to the time it stops; and (ii) the number of gallons (incl. partial gallons) it pumps during that time. For me, it was easiest to get these data in two steps. I took a one-gallon pail to my laundry sink, let the water run (fast, then slow) until the pump kicked in (light flickers when this happens), quickly close the faucet, and then start filling up pails and dumping them until the pump kicks in again (flicker). I did this a couple of times and took an average. Then I put away the pail and got out a clock with a second hand, and slowly drained the system until the pump kicked in (flicker), and counted the seconds until the pump stopped (flicker; click). I did this a couple of times and took an average. Number of gals divided by number of seconds times 60 = GPM "flow rate" of your pump.

    Next, calculate tank size by multiplying the flow rate by between 1 and 2 (assuming you have a 1/2 or 3/4 hp pump, as most homes do). The principle is that the pump wants at least a minute to cool between cycles, for best service life. The longer, the better (1 minute is a minimum recommendation). For example, if you have a 10 gpm flow rate pump like mine, you want at least 10 gals "draw down". The draw down is the number of gallons the system/tank will put out until the pump has to kick in again.

    Draw down is determined by (i) the size of the tank, (ii) the cut in/cut out pressures set by the switch, and (iii) some more esoteric factors such as elevation, etc. I found a factor on the web that told me that with a typical 40/60 cut-in/cut-out pressure such as mine, the draw down will be approximately .26 X "total volume" of the tank (expressed in gallons). Total volume is the total physical volume of a tank (the water side and the air side of a bladder/membrane tank; IGNORE the "equivalent" figures published by some web sites, which just confuses things to no end). So, a 44 gal tank will have a drawdown of 44 X .26 = 11.44 gallons. The pump will run a bit more than one minute each time the switch calls for more pressure, and will get at least a minute rest between runs (assuming not more than 10 gpm draw at all the faucets at one time).

    Tank manufacturers also publish drawdown for their tanks. Amtrol's figures seem generous; perhaps they have designed their tanks to yield slightly more drawdown per total volume than other tanks. More drawdown is nothing but good for the pump and for your electrical bill -- it means the pump cycles less. The only disadvantages to a bigger tank are: extra up-front cost; slightly more space requirement; the extra weight for whoever has to carry it to the basement/garage/etc. Another advantage of a larger tank is that the fewer cycles (theoretically) will result over time in less flexing of the diaphram, so that the tank should last longer. I do not know of any empirical data to back this up, but it makes intuitive sense to me.

    There is a whole other debate (kind of exhausting, actually) about using CSVs (Cycle Stop Valves, a proprietary pressure regulator) and smaller (e.g., 4.4 gallon) captive air tanks, rather than the traditional layout described above. The moderator of this forum (valveman) is the inventor of this device and has a web site dedicated to it, and extremely knowledgeable. If you have a heat pump and/or do lots of irrigation, you might find this to be a better setup, and the time to make that decision would be before you replace the tank. For me (2 people; 1.5 bath; no irrigation or heat pump; renting) I preferred the lower electrical usage of the traditional set-up, and have asked the landlord to install a 40+ gallon Amtrol or Flexon tank. Good luck!

    p.s.: You probably want to nail down any modifications to your set-up before installing the new tank (e.g., acid neutralizer; chlorine-injection pump), so that those fittings can be plumbed in at the same time. Moreover, a union installed between the "T" and the tank would make future service/change of the tank much easier.
     
  5. valveman

    valveman Moderator Staff Member

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    Drewmcg, I applaud you for all the research. You have certainly done your homework, but I disagree with your conclusion. You should have noticed during you draw down and run time testing that the “flicker” is not a good thing. Even with no irrigation or heat pump, you would still benefit from a CSV and a smaller tank. With the CSV your pressure would stay constant while taking a shower instead of cycling on and off and “flickering” the lights several times while you are in the shower. Showers are much better and more enjoyable when the pressure stays at a constant 50 PSI with a CSV, instead of cycling on at 40 and off at 60 over and over again.

    The electric bill for a pump used strickly for a house is only about 5 bucks a month. The CSV should not increase the electric usage, but the worst case would be to add about 3 bucks a month to the electric bill. It would take many years to make up the difference in cost of a 44 gallon tank compared to a 4.4 gallon tank at 3 bucks a month. And that is not even considering the extra life the CSV will add to your pump, pressure switch, and everything else in the system that cycling normally destroys. Your landlord would be wise to do his own research and install a CSV to make his pump system last longer. As a renter you would like the constant pressure. But if you have never experienced constant pressure, you don’t know you are missing something.

    The debate is “exhausting” because there is nothing intuitive about a pump system. Everything is opposite of what you would think. Pump installers with many years of experience still do not understand, as they also think it should be intuitive, and its not. Pumps are not suppose to cycle on and off, they are made for “continuous duty”. Restricting a pump with a valve actually makes its work easier, not harder as you would think. And smaller tanks are now better than large tanks, so you don’t experience such long intervals of high and low pressures.

    A so called “properly sized tank” is what the pump, motor, and tank companies want you to do. That way they can predict a short life span for your pump system, and get to sell you about 3 or 4 pumps and tanks instead of one in 20 years. If I were doing a bucket test and trying to be intuitive, I would probably come to the same conclusion. However, decades of experience and replacing thousands of pump systems has taught me that eliminating cycling is the best thing for a pump system.
     
  6. devans175

    devans175 New Member

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    I tested my flow rate according to instructions I got when I purchased my acid neutralizer. It's 4 GPM.

    The fittings are where I'm running into problems. The calcite/corosex neutralizer I settled on and purchased instructs you to install it after the tank, thus leaving the tank vulnerable. Even if the tank itself is impervious, the point that you connect to the tank may not be. I'd prefer to eliminate the metal fittings and connections on the untreated side of the system.

    I found a web site that performs the calculations. Here's the link:
    http://wellmate.com/en-US/support/calculator/

    Based on what I've read here and elsewhere, I think I'm going to go with the 40 gallon.
    Thanks!!
     
  7. valveman

    valveman Moderator Staff Member

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    No problem. Like I said, if you have never had constant pressure, you will never know how good it could have been anyway. BTW, a CSV will still work with a 40 gallon tank. But after you see how a CSV works, you will know the 40 gallon tank is excessive.
     
  8. Drewmcg

    Drewmcg New Member

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    Not to quibble, but if the landlord pays $500 for a quality 44 gal tank (plus installation), rather than $250 for a CSV + quality 4.4 gal tank, then the delta is $250. (I acknowledge that these figures might be off a bit.) In S.E. Michigan, marginal electricity costs 12.5 cents/KwH. I've seen you use 7 cents and 10 cents/KwH for your dollar/month calculations, so do not know what figure you used for $3/mo. Assuming $5/month penalty with the CSV and a 15-year tank life, the extra $150 for the 44 gal tank setup would pay for itself in 50 months (50 X $5 = $250); or in 83 months at your $3/mo. figure (83X $3 = $250). If the tank lasts 15 years, the extra investment will pay for itself two or three times over in that time frame.

    Of course, this does not consider pump replacement costs. In a low, intermittent use context such as mine, I know of no empirical data on pump failure differentials. The difference in pump cycles in my application between the 44 gal tank and the CSV/4.4 gal tank setup would likely be minor (maybe only 3 cycles a day). That's a thousand cycles a year, which seems minimal in pump life expectancy terms.

    As far as the shower goes, I use a low-flow showerhead (under 2 GPM) to save energy; I do not expect the pump to cycle more than once per shower--which it would do with a CSV setup anyway. The flicker is seen on basement incadescent, not my shower CFCs. That leaves the pleasure of constant pressure v. average pressure with a 20 psi differential. Not a big deal to me, but others might disagree. (P.S. If I had a high/persistent water use situation, I'd be sold on a CSV.) Cheers!
     
    Last edited: Jun 21, 2011
  9. valveman

    valveman Moderator Staff Member

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    It has been my experience that the time it takes for a big tank to pay for itself in energy savings is about how long the tank last. So the big tank is not really saving anything. I have also tested systems with low flow shower heads and have found that they don't really save water. People with 2 GPM shower heads just take showers that are twice as long as people with 4 GPM shower heads. With low flow shower heads it takes twice as long to get the soap rinsed out of my hair. But I know people who use a hand wand and take a Navy type shower. Now that is conserving water. I want a shower with good pressure and feel cheated when I don't get it.
     
  10. Bill Berry

    Bill Berry New Member

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    I'm in the process of completely changing out my deep submersible pump and well water pressure tank and I've done so much reading on this my eyeballs are about to jump out of my head. I want to take this one step at a time but the first thing I want to do is learn what is the proper size pressure tank. The math in my head keeps telling me I need to go small due the amount of water my pump could draw at any one time, generally one minute, but regardless of whether it's 5 GPM or 10 GPM, I don't understand how one goes about preventing one's pump from burning up when you have pressure tanks that have up to 119 gallons (300 gallon equivalence) and the math says, that's 12 minutes to fill up at 10 GPM and no pump is going to run that long, yes? These cycle stop valves; don't they in essence make your pump run constantly? Now, if a smaller pressure tank is in order, I want to add a 250 gallon water storage tank, but first things first; thank you!
     
  11. Reach4

    Reach4 Well-Known Member

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    To prevent damage to your pump due to running out of water in the well, you can put a device that looks for that condition and shuts the pump down for a while. If you don't run out of water, it is OK to run your pump for a long continuous period -- even 24 hours or more. The water being pumped cools the pump.

    A 119 gallon pressure tank will have a drawdown of about 31 gallons. See http://www.amtrol.com/media/documents/wellxtrol/MC7025_04_14_WXTsizingCard.pdf
     
    Last edited: Jul 20, 2015
  12. valveman

    valveman Moderator Staff Member

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    Like Reach says a 119 gallon pressure tank only holds about 30 gallons of water. And although it does not hurt a pump to run for 3,6, or even 30 minutes to fill a pressure tank, A CSV can be set to just top off the last 2-3 gallons in the tank at 1 GPM, leaving a 2-3 minute pump run time. Water comes from the pump/well and not the pressure tank. So you really only need a 4.5 gallon size pressure tank that will hold 1 gallon of water. The CSV will make the pump run continuously as long as you are using more than 1 GPM. With a CSV the water goes right past the pressure tank, straight to the faucet, so it doesn't matter if it is a 1 gallon or a million gallon pressure tank.

    And you can't count on a pressure tank to have any stored water. With a 40/60 pressure switch you will most likely (Murphy's Law) be at about 41 PSI when the power goes off and the pressure tank will be empty. A full storage tank like the 250 gallon you describe is the only way to be sure and have some water stored for times when the power is off. But then you will need an additional pump to pump water from the storage tank, as the well pump will be used just to fill the storage tank.
     
  13. Bill Berry

    Bill Berry New Member

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    So there is no harm running the pump continuously while taking a bath or watering plants outside? The function of the CSV is to prevent the constant start and stopping of the pump and allow it to bypass the pressure tank and send water directly to wherever you need it, but what about the pressure? Is there any harm to running it for a few minutes or longer at a time?
     
  14. Texas Wellman

    Texas Wellman In the Trades

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    Most of the metal tanks I am familiar with do not have any kind of lining in them (aka, glass lining like a water heater or epoxy lining). Most are simply galvanized metal. They will rust out in short order when exposed to low pH water.
     
  15. Texas Wellman

    Texas Wellman In the Trades

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    I have always found that the longest pump life results in the smallest pump that will adequately do the job paired with the largest tank one can afford. This and relatively good quality water.
     
  16. valveman

    valveman Moderator Staff Member

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    Pumps are made to run 24/7 and will last longer when doing so that when starting and stopping. You want the pump to run for as long as water is being used. The pump should not go off until you turn off all the faucets.
     
  17. valveman

    valveman Moderator Staff Member

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    This is the way we use to try and extend pump run times, which is why it makes pumps last longer. But even the largest tank will not let the pump run continuously when using water like a CSV will do. Large tanks just reduce the number of cycles, the CSV eliminates cycles for as long as the water is being used. Look on the side of the motor. It will say made for "continuous duty", which again will make pumps last longer than any amount of cycling on/off.
     
  18. Bill Berry

    Bill Berry New Member

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    Thanks you for all the replies; okay, so if the pumps are made to run continuously so to avoid constant start/stop cycling, what is the point of having the pressure tank to begin with, why not "not" have one.? Where is the CSV installed at? Last question, is there a benefit to installing on the system a (250 or more) gallon water storage tank between the pump and the pressure tank and use a shallow jet pump prior to the pressure tank?
     
  19. craigpump

    craigpump Well-Known Member

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    You need a tank to act as a buffer. Without a tank the pump would cycle rapidly as the water in being used and the pump would have a very short life.

    I personally do not like static storage systems, especially in basements.
    They sweat
    There is the ever present potential for leaks
    Water level control systems are not 100% fail proof
    The tanks are are subject to contamination
    Most control systems are way to complicated for most pump guys to troubleshoot and repair and parts may not be readily available. Especially on weekends, holidays......

    In other words, I like clean, simple and easy for anyone to service.
     
  20. valveman

    valveman Moderator Staff Member

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    I agree with craigpump. I would not want the hassle of a storage tank and booster pump as long as the well can supply at least 5 GPM. Most wells have a little water stored in them so you can usually pump 10 GPM for a short time when needed, even if the well doesn't make that much on the long term.

    You need a pressure tank. But with the CSV you just don't need a very large pressure tank. The 4.5 gallon size tank holds about a gallon of water. This will fill the icemaker or wash a toothbrush, but the pump will have to come on for other things like showers, even with a larger tank. So then the size of the tank doesn't matter as the CSV makes water go right past the tank to the shower. Water isn't compressible, so without at least a gallon in a pressure tank, the pump would come on if a faucet drips even two drops.

    Even with a small tank the slow tank fill rate (1 GPM) of the CSV gives the pump some run time after all the faucets are closed. As we have said, run time for the pump is a good thing. Without a pressure tank the pump would shut off instantly after you closed the faucet, or even after two drops came out of a leaky faucet. The trick is to keep the pump running continuously while you are using water, and to give the pump a little run time after the faucets are closed, which is exactly what a CSV does, even with the small tank.
     
  21. Bill Berry

    Bill Berry New Member

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    Thank all of you so much for the advice; it is deeply appreciated!!! I drive 260 miles a day to and from...and it's mostly rural and no city water services; I've seen one water storage tank and that's it for residential homes; I've seen a bunch of them out in farm fields where irrigation is being done. Additionally, I saw a lot of "dog houses" that weren't tall telling me that whatever tank they're using were small and that's been the advice here thus far. One more request; a good deep submersible? I've bought a pair of 1/2Hp 230v Flotec deep sub pumps; the first one ironically is my last one that I used twice; in the end it was the pressure switch and the pump was good, so I kept it as a backup; the tweener was another Flotec based on the specs of the 1st (last) one I pulled up; it lasted 5 years. I'm replacing the pressure tank with this next installment of a pump. Are the Amtrols as good as they say they are or will the WaterWorker do just fine?
     
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