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We have a well supplying 14 cabins on a mountain. The two cabins at the top have a maximum of 25 lbs of pressure at times while the cabins at the bottom have plenty of pressure. What is the easiest and most economical way to increase the pressure for the two cabins at the top?
It would seem that the problem is the gain in elevation as you move up the mountain. You could put a booster pump in at some point. You might also consider putting the pressure tank at the highest cabin. Let the pump pump up the mountain to the tank. Then you could use some pressure regulators as you go down in elevation to prevent pressure from getting too high. Still, it's hard to say when we have no idea of what the setup looks like. I would assume you have a pretty good pump and something on the order of two inch pipe going up the mountain?
Thank you for your reply. You are right on it. Our (HOA) problem is the elevation of the top cabins at the end of the water trunk line. Our two otions, as you stated are: either install a booster pump directly below those two cabins, which we understand would be an expensive operation or a well system pressure tank at the one cabin who has the concern. The homeowner has stated that he would be willing to pay for anything that would help. His main concern was that when he did have acceptable pressure (28-30lbs), he would sometimes loose all pressure, sometimes while even taking a shower. Thus as we understand it, a pressure tank with an adequate water reserve would not increase his pressure, but would sustain the pressure and lessen the times the pump below would be cycling.
If it is just one cabin, then I believe a booster pump is the way to go. Putting a pressure tank there will not increase the pressure at the cabin, as you stated. I'm not sure that you will gain anything at all. I guess if you put a checkvalve downhill of the tank, then it would possibly sustain the pressure a little, but I just don't see that as being much of a deal. The booster pump would help as long as your pipe can deliver enough water.Quote:
Thus as we understand it, a pressure tank with an adequate water reserve would not increase his pressure, but would sustain the pressure and lessen the times the pump below would be cycling.
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Originally Posted by jlisenbe
Well, one more item. When your pump has cut off at whatever pressure that happens, then I am assuming you are saying that, with no water being used anywhere else, the pressure at the two upper cabins is around 25 pounds. If that is the case, then I'd suggest a booster pump. Bear in mind that you lose about 0.4 pounds of pressure for every foot of elevation. So if the upper cabins are, for instance, 100 feet higher in elevation than the pressure tank, you lose around 40# of pressure just to move the water that high. So if your tank is at 65#, then you can see why the upper cabins are only getting 25# or so of pressure.
How would a booster pump affect the water pressure of the cabins below the top two? I would assume the pump would have to draw off the water source below if not off a reservoir. Again, we only have one homeowner complaining and their main concern is that when the pressure is acceptable, they loose the pressure for a period. Would not the presssure tank with a 44 gal reserve under the bladder help sustain his pressure?
The pump below is drawing off a large reservouir that is supplied by another pump further below in the well. The pressure switch at the reservouir above serving the 14 cabins above through a trunk line up the mountain, is set at 115 lbs by our well company.
If you put a tank at the cabin, I'd put a checkvalve "behind" it. Otherwise, it will just feed water backwards when other cabins draw water. If the tank had water at, for instance, 40#, then the cabin would have some reserve of several gallons (depending on the size of the tank). However, you stated above that the cabin has a MAX of 25#. If that's the case, then you will never have more than 25# and most people would not be happy with that. But it might help some.
A booster pump, on the other hand, should keep a fairly steady pressure as long as your system can supply it with enough water. If you don't have enough volume, then I would not think it would work.
Have you asked your well company for some advice? They know the system better than anyone.
Pressure up the mountain has two components. A gravity component which you can no mitigate without booster help. The other is pipe size resistance. Increasing pipe size will drop that component down. Gravity must be over come by some other means such as a booster pump. If all cabins below are supplied with pressure regulators, then their flow will be limited by their pressure regulator setting regardless of how much head pressure is attained. A properly sized booster pump hooked to a variable speed drive with its speed and torque regulated by the pressure at the highest point will keep a reasonably steady pressure in the system if properly designed. The pump will run as needed and at a speed and torque to maintain proper pressure in the system. This requires a little engineering, but this is more cost effective in the long run because the pump will only run at the speed needed to supply needs and at the torque to maintain pressure. When little or now water is needed the pump runs slower or at zero speed. As more water is needed the pump speeds up to maintain pressure at top cabin. The current or torque of the pump will be regulated up and down automatically and not be running above and below requirements. A simple pump without the drive will not do a great job of maintaining the flows and pressures at different usage rates. Think about it
Boy, that makes a lot of sence. Nobody has suggested a booster pump with a variable speed drive regulated by the pressure at the highest cabin. At what point in the trunk line would you locate this pump?
In talking with the tech at Water Worker Pressure Tanks, he said that he would love to sell us a pressure tank, but he didn't think that would solve our problem. He said. with a pressure tank, when the homeowner looses pressure and you are using the water in the tank and as the water decreases in the tank, so does the pressure. He said that we need to time just how long a period there is between when we have adiquate pressure and loose it and when we retain adequate pressure. That may help us better define what our options are.
By the way, I really appreciate your help and advise.
Might want to slow down just a bit. You currently have a system installed which, you said, maintains 115 pounds of pressure at the bottom of the system. That is a lot, and I'm sure you must be using pressure regulators in at least the first few cabins to mitigate that pressure. Your problem has two concerns:
1. As you gain elevation, you lose pressure. That is definitely an issue with your system.
2. As people in the cabins use water, volume comes into play. When a lot of water is being drawn at one time, perhaps your pump can supply that much water and perhaps it can't. If it can't, then pressure at the top of the hill will suffer even more than usual.
A conventional booster pump, or even a variable speed type, at the top two or three cabins can solve problem 1. It will not solve problem 2.
Variable speed pumps only have one advantage that I am aware of. They can maintain a pretty constant pressure in the system. If you set the pump for let's say 60 psi, then it will maintain that at all times.
Conventional systems with pressure tanks have a regulating switch which maintains a range of pressure. It might turn to pump on at 40#, for instance, and then off at 60#. So you have that cycle of slowly going from 40 to 60 and back again as water is used. I am assuming that is the kind of system you have, except at a higher pressure. They are quite common. Please let us know if that is not the case.
Here is the point. Unless you increase the 115# at the bottom of the hill, you will not increase the pressure at the top of the hill without installing a booster pump. I don't see any advantage with the variable speed pump, and it is significantly more expensive, especially if you are thinking about putting one in as your main pump in the system.
Check this out for yourself. Bear in mind that the price is for a pump for one or two cabins, not for the whole system. A conventional booster pump is at the bottom of the page. Again, I am not wildly familiar with variable speed pumps, but I don't see how a pump of that type is going to be a difference maker in your case. If the pump you have now can supply enough water for all the cabins, meaning that volume is not a problem, then a new pump at the bottom of the hill doesn't help you.
http://www.bigbrandwater.com/grundfosboost1.html
I wouldn't suggest a new pump at the bottom. When no water is moving, pressure at all points in the system is at the same pressure! I assume 115lbs. When water starts to flow, then water moves to the point of least resistance- the lower cabins. If the lower cabins are regulated at 40 PSI then their flow is unlimited until the pressure in the whole system drops below 40 PSI, which means multiple users at the same time. The big questions is with the variable speed pump is can the well supply sufficient water if enough users are exceeding the output capacity in flow or GPM of the well pump? At some point everyone will start to loose flow. The only way to manage this is to provide larger pump at well. I am not suggesting a large well pump! Assuming the well pump is sufficient for the calculated total residential use. The problem as it stands given that the well pump is large enough, is that the head resistance and pipe resistance is large enough to restrict flow to the top cabins with 115 lbs. pressure at well pump. If everyone but the top cabin is not using water then more pressure and flow are available for the top cabin. As soon as users down the hill start using water the pressure in the whole system will drop and the flow at the top will be reduced accordingly. If a booster pump is inserted in the proper location and the well pump can supply enough water so the booster pump won't start sucking air, then the booster pump on a variable speed drive can regulate the pressure and flow at the top cabin. I hate making recommendations without knowing all the facts and capabilities. Small horsepower inverters are becoming very reasonable in price, the issue might be getting power to the inverter. You will want to place the inverter as close as you possibly can to the booster pump(less than 25' best) and you want to put the booster pump probably at a point where you start to notice significant problems- somewhere above the lower cabins I would think. I am new at this- trying to explain things without getting bogged down in semantics, but a little understanding of resistance and flow in parallel come into play. I know there are some pump people in this discussion and I don't discount their input. I have a 30 + year experience with AC and DC variable speed drives, servo and proportional hydraulic valves etc. Theory is pretty much the same, application has its own personality which your pump people will know more about. I am not selling anything and am trying to just be a contributor to a list of options. If this was different than a basic chat room, we could sit down together and bang out the theories and decide on the best course of action. That doesn't mean there are better or more efficient ways to do things. The best thing I can tell you is the KISS formula(keep it simple stupid). The most simple and cheapest things are generally the best if they accomplish what you want them to. If you choose that route and it doesn't work then you pay for a solution that didn't work. The more that don't work the more you spend to eventually until you come with the solution that does work. I don't engineer water systems. I understand resistance and pressure and flow to some degree, but my answers are based on theory not the final design characteristics. My suggestion is to find the right people to redesign your system. My basic thoughts are: put regulators on all cabins, make sure that well pump has sufficient output for possible demands and go from there. I installed a pump 125 horse power pump almost a mile away from our facility. We were allowed to only pull a maximum GPM or it would drop the water table too far, so we regulated flow- which was in this case proportional to the speed of the pump. We used WIFI radios to control the pump. There are so many options. Cost? Value? You need to decide. All you pump guys feel free to slap me around where I am wrong. I don't want to mislead anyone.
It all comes down to two things: pressure and volume. He starts with 115 psi. Hard to imagine how to increase that. At the top cabin it is down to 25. I don't know of anything to increase that other than a booster pump. But as I stated earlier, I'd suggest he get with his well company and see what they suggest. They know the system. I am still thinking about the possibility of putting the pressure tank at the top cabin instead of at the bottom of the mountain. Let the pump pump up to the tank. Everything is downhill from there.
The more I think about it and we simulate the problem, the more I feel putting the pressure tank at the top instead of at the bottom is the answer. We have another well system on the other side going up that road to the top of that mountain with the pressure tank near the top and that homeowner at the top, never completely looses water. They don't even remember loosing pressure. When testing the problem at our other well system at the cabin with the problem and that pressure tank and pressure switch at the bottom, it took 3 1/2 minutes with the shower faucet on for that water pressure to go from 25-30 lbs to 0 and start to go back up again. It took that long for the pressure tank and pressure switch to recognize a drop in pressure. The two water systems are identical except for the location of the pressure tanks and switches.
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