What's the rule for PVC pipe size vs flow?

Discussion in 'Plumbing Forum' started by jmr106, Nov 27, 2016.

  1. Nov 27, 2016 #1

    jmr106

    jmr106

    jmr106

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    In the near future, I'm going to be installing a large sump basin (50 to 70 gallons or so) in the crawlspace with two new pumps that are more efficient and will kick out even more water with little noise. Each pump will have its own pipe with a roughly 7' initial head, then both will run about 5 feet horizontal and go out of the crawlspace to the outside, make a 90 degree turn and somewhere around that area just outside of the house it will split into a single PVC pipe to continue the 20-25ft run out into the back yard. The pumps can handle it and are designed for up to a 25ft head with no problem.

    I'm doing this joining of the pipes outside because if the two pipes joined a single larger pipe inside of the crawlspace and something happened to the larger main pipe, that would be a big failure. However, with two separate pipes going outside, there is a backup and it would at least get the water outside of the house even if the split to the large pipe came loose outside of the house. I just like to plan ahead of time.

    I talked to the guy at the place where I'll be buying the pumps. He told me, "I would suggest that you tie those two discharge pipes to a minimum 2-1/2" or even 3" PVC pipe for maximum performance. As long as the horizontal pumping distance is not extreme, you will be fine." Is it really that simple - doubling the pipe size to whatever the main pipe is to be? My research hasn't been coming up with that.

    One will be primary and one for backup. Each pump can kick out about 3,330GPH, or roughly 55GPM. In the rare crazy rain event where both need to come on and 110GPM is going through one pipe, I want to make sure it is big enough. However, apparently a pipe that is too big has the opposite effect - losing pressure to push the water out fast enough and with enough force.

    Suggestions? I have done Google searches and such, but there always seems to be conflicting information. One place says x thousands of gallons should flow through x size pipe, and then another place says something totally different. I want maximum flow rate for each pump without losing the pressure.

    I really need to angle the entire horizontal pipe run (the part that runs along the ground) a little bit somehow, so that nothing freezes in the pipe during the winter discharges.
     
    Last edited: Nov 27, 2016
  2. Nov 27, 2016 #2

    frodo

    frodo

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    each gpm = 2 fu both pumps running = 220 fu

    220 fu minimm size discharge is 4'' both pumps tied in

    3'' minumum seperate

    chart.jpg
     
    Last edited: Nov 27, 2016
  3. Nov 27, 2016 #3

    jmr106

    jmr106

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    Sump pumps. After a lot of research, I'm going with dual 1/3HP Ion Storm Pros. Stainless steel. Total 4.5 running amps each, but kicks out as much as some 1/2HP pumps that use way more amps. It utilizes a digital level control, solid state with no moving parts to wear out. I'll either elevate one above the other somehow as strictly a backup pump sitting on something else in the basin. Or maybe I'll use the digital on one and the float switch on the other for higher volume.

    [​IMG]

    [​IMG]


    Impeccable reviews and pretty much special order pumps.

    I'm technically going to be using a sewage basin for the sump basin, because the regular sump basins aren't typically made to that size or they want $500 for an equivalently-sized sump basin that looks virtually the same as the sewage basin.

    Storm water.
     
    Last edited: Nov 27, 2016
  4. Nov 27, 2016 #4

    frodo

    frodo

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    make sure it seals tight, it is a blooming high way for crawly things
     
  5. Nov 27, 2016 #5

    jmr106

    jmr106

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    The sump pit itself? I'm planning to get the matching lid with the custom holes with rubber gaskets around them, a hole for electrical, etc. Trying to figure out if there is some kind of flap that I could put on the end of the discharge pipe that would close down and prevent any critters from getting into the pipe when it isn't discharging. Sort of like what we have on the dryer vent.

    Are the gate valves simply there as a means to keep any water in the pipe above from getting everywhere if a pump needed to be changed out or one side turned off for some reason?

    Is a weep hole really necessary? I have been reading a lot about people drilling a weep hole in the pipe just above where it attaches to the pump to prevent some sort of air lock, but my current pipes do not have that. Haven't had any air lock issues on either pedestal pump.
     
    Last edited: Nov 27, 2016
  6. Nov 27, 2016 #6

    frodo

    frodo

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    use a 4'' pvc backwater valve

    code calls for the valve to be installed,,,

    weep hole, do what the manufacture of the pump requires, some call for it others do not
     
  7. Nov 27, 2016 #7

    frodo

    frodo

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    you NEED to wire your pumps to lead/lag

    pump 1 comes on, pump 2 will come on if high water is detected

    then the next cycle

    pump 2 comes on, pump 1 will come on if high water is detected

    then next cycle

    pump 1 on pump 2 if needed

    etc etc...

    you do NOT want one pump sitting there not being used

    cyberheater2.jpg
     
    slownsteady likes this.
  8. Nov 28, 2016 #8

    jmr106

    jmr106

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    There are some pump controllers that I have seen that do this. That's about the only way that I know of to do that. Unless we're having a really rainy season, the pumps don't get a lot of continual use. Our issue is more so...when it decides to rain for 2-4 days straight. The pumps might come on for a day or two after that, maybe averaging 30 gallons per minute coming in when things have calmed down. Or a random thunderstorm that dumps so much water at one time that I get 80-100 gallons per minute flowing in for maybe 20-30 minutes and then it goes away. I'm going to be using a basin surrounded by gravel. Due to the size of the basin that I'll be getting, I'll have to punch holes in it myself. I'm trying to figure out a way to have holes in the basin so that water will flow in and the basin won't push up, but also...figuring out how the heck I would test it if any water that you poured in would seep out of the holes into surrounding gravel. Both of the pumps will need to be tested regularly since it doesn't get water flow all of the time. I could leave some of the bottom of the basin solid without holes in it, but I'd have to make sure that it doesn't cause it to float.
     
    Last edited: Nov 28, 2016
  9. Nov 28, 2016 #9

    frodo

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  10. Nov 28, 2016 #10

    jmr106

    jmr106

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    I'm tackling an issue in an icky crawlspace that I've had other threads about. Its a dug-out portion of a crawlspace approximately 15'L x 4'W x 3'H with a retaining wall around it. 2-3 days of rain and the rain comes in through the wall from seemingly all sides. Suspected that an old septic tank about 8-10 feet outside of the house (which has been found and filled with dirt since the last rainfall that triggered the pumps) may had something to do with it, as a potential "water flow hole" was found in a corner of the outside of the wall months ago. Got about 2.5 inches of rain coming up over the next few days, so if it triggers the pump, I'm going to see if a lot of the water was coming from the old septic tank that may have been filling and making its way to the crawlspace a few feet underground.

    The only solution found after months of pondering and research was to fill that whole area with drainage gravel and install a big sump basin and strong pumps. The flow may be less now, but with a saturated ground when it rains, I still expect some to come in. So I'm installing a proper sump (which it doesn't have at the time) to deal with it.

    So in this case, we're talking a ton of gravel all the way around and no sump pit. Just a basin. Water would come from all directions in the gravel, so a basin with holes around it is needed to let the water in. There is no proper water outlet pipe to connect to the basin, so I'm struggling to find a way to make a basin that won't float itself out of the gravel and yet will somehow allow me to keep a bit of water in it when I want to test the pumps. Otherwise, putting water in the basin with holes in it would make it just flow out into the surrounding gravel that the basin is in. I could leave maybe a foot or so of the bottom of the basin without holes in it, but the only concern with doing that is the potential for it to float. Of course, each pump is about 25+ pounds. I'll probably stick some kind of brick or something in there to elevate pump two so that it alternates somehow, or I'll get a pump controller of some sort. Working with the manufacturer on that currently to see what they recommend. Most basins are little and therefore the drawdown is about 6" to 10" max for the average pump. I'd prefer to pump out way more than that at once to prevent short cycling and just to keep up with any heavy water flow that it can get sometimes.
     
    Last edited: Nov 28, 2016
  11. Nov 28, 2016 #11

    nealtw

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    Run a loop of perforated pipe around your pit close to floor level and have it enter the pump box after a back flow preventor, drill the rest of the holes in the sides above your start level. That way you could check run your test and insure there will always be water in the bottom so it can't float.

    You are going to seal the pies in the lid, are you going to run a third pipe or hose to the outside for testing?
     
  12. Nov 28, 2016 #12

    frodo

    frodo

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    my thoughts, sounds like you need to build a pit, the poly, will keep the water from undermining the pit


    the top, of the mesh would be the same elevation, as dirt level of the area to be drained

    jjjjjjjjjjjjjjjjjjjjjjjjjjjjjjj.jpg

    2016-03-14_0929.jpg
     
    Last edited: Nov 28, 2016
  13. Nov 28, 2016 #13

    frodo

    frodo

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    ..........


    hince the drawing
     
  14. Nov 28, 2016 #14

    jmr106

    jmr106

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    So a basin itself in the gravel will probably float or move out of place?
     
  15. Nov 29, 2016 #15

    frodo

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    an area drain will catch surface water

    a french drain collects water below ground

    a pit collects water from pipes

    you have suggested you want to use a sump pump pit

    and you have suggested using a basin

    i do not know which you are actually going to use...

    a basin, out of concrete will not float. IF you use the poly apron to keep the water from under mining


    if you use a pit [store bought] to collect surface water, you will need to concrete a floor

    to channel the water to the pit

    if you want to go cheap...use a 5 gallon bucket, drill holes in it

    put the pump inn the bucket, dig a hole
     
  16. Nov 29, 2016 #16

    nealtw

    nealtw

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    the bottom o the sump will be at the level of the old floor and with water coming in at floor level it's level should always be equal to the outside water.
    http://www.houserepairtalk.com/showthread.php?t=19909

    If it does need concrete for weight, I think it is total cubic ft / 15 but boats with holes don't usually float.:p
     
    Last edited: Nov 29, 2016
  17. Nov 30, 2016 #17

    jmr106

    jmr106

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    I could prod around on the floor in the hole with something and see if there is concrete underneath it. A lot of people seemed to establish somewhere back in that post (that Neal linked to) that the floor would have to have concrete or it would have fallen in long ago. That system is on a cement slab that weights quite a bit, then back in the corner, there's a 40 gallon water heater sitting on the dirt. That's probably pushing 500 pounds including the water. Beside where the pumps are, there is a cement ledge of some sort visible, as well.

    The plan is already pretty much set in stone to hang the furnace from the floor and elevate said water heater. So basically I'd be left with the hole to figure out what to do with. The thing that I find irritating is that I'll likely only be able to get 30" of height for elevating that water heater due to the fact that they don't make them any shorter than about 46" to 48". I thought that lower capacity would make it a bit shorter, but they actually have some 30+ gallons pushing 54" tall and even taller than the 40 gallons. So, that's only about 30" or less max of gravel that I'd be able to put down. The only way to use the larger basins that I found (24"W x 36"L) would be to put gravel down into the existing sump hole and level it out so that only 6 inches of the basin would go down into it and rest on the gravel. Then the other 30 inches would be flush in the 30" of gravel and theoretically the lid of the basin would be flat or just slightly above the top of the gravel. Not sure how feasible that is going to be. We've pretty much covered the fact that an electric is out of the question. Not enough extra amps in the current breaker setup for that. External water heaters...I used to consider that, but I've had so many people tell me how unreliable they are and how often they break/need to be replaced that I don't want to even bother with one anymore. I'm beginning to think that I need to special order a shorter water heater (I've been told that there are some out there), but it might be fun trying to find someone willing to install it on-hand already.

    I could use concrete to build a pit of some sort, and I get the general idea of your diagram. I just don't know how the heck to form such a shape with concrete without customizing a bunch of wood for a frame until it set. I'm pushing 45+ hours per week on average at work, so that extra time can be interesting to find. At the same time, whatever the solution is that will be used, I want to do it right the first time.
     
    Last edited: Nov 30, 2016
  18. Nov 30, 2016 #18
  19. Nov 30, 2016 #19

    jmr106

    jmr106

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    Yeah, I'd love to get one of those if it could handle it. Just don't want to throw another $2K to $3K out there for another breaker box installation just for that. Apparently they used to make these lowboys in natural gas, as well...but discontinued them because they weren't that efficient or something like that. I think it was something to do with the inside flue not being long enough to be efficient?

    Basically from the floor to the floor joist is about 84". The estimated 30" elevation for the water heater is all that I could do if I got a water heater that was 46" or so tall. I factor in about 8" inches for the flue and such and a little distance from the joists per whatever the code requires in my state of Georgia. If I could find a 40" water heater...I'd have 36 inches (the whole wall is about 3 feet tall total) plus 8 inches extra for the flue or whatever. Then I could add more gravel or just not have to worry about it flooding even if the power/pumps went out. It would be elevated at the top of the wall where it wouldn't flood anyway. Ideally, that's my goal. Pumps would be just to keep it not so moist down there, in that case.
     
    Last edited: Nov 30, 2016
  20. Nov 30, 2016 #20

    frodo

    frodo

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    back in the 50's. they use to install water heaters. half in the attic.

    the top of the heater was in the attic, the bottom was in a closet.

    what do you have above you ?


    I closet ?

    on demand wtr flow.jpg
     

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