we have high water table. sump pump runs a lot with the old pressure switch at the bottom of the pit. sick of the constant pump cycling.

so I unplugged both pumps to see how high the water would go. it stopped rising about 8" below the top of the pit, and about 1/2 way up the 4" drain tile pipe.

I also have a vertical float switch. can I just set it to turn on at just above the water table level?

I know it is better to have the pump turn on before the water level reaches the drain tile -- but how bad is it to just leave the tile 1/2 full of water? will this cause foundation issues or excess hydro pressure on the slab or anything?

I really don't care about the cost of the constant pumping. it's the general nuisance of having water constantly rushing in and pumping out.

 

It is okay to leave the pump stopped with the drain tile pipes halfway submerged, if the water stops there.

As conditions including rainfall change, the stopping place for the water may vary. If the water stops rising just over the tops of the drain pipes and you leave it that way, then you may start to see water seeping up onto the floor at the opposite side of the basement. If this happens you may need to lower the float turn on level again and keep the pump going on and off for a week with most of the drain pipes not submerged before the far side dries out again.

While you are at it, inspect the sump pump outlet pipe to be sure it is not leaking outside near the foundation and the water is being dumped some distance away and no other water is accumulating near the foundation.

 

funny you mention the discharge pipe. we just bought this house last year. previous owner had clearly struggled with the water & sump pump (and I knew this going into it...) he had the pump discharge into a section of *perforated* black corrugated drain pipe right next to the house that was further tee'd into a main gutter downspout -- all of which then fed into a collapsed, clogged corrugated pipe that had somehow been crunched into a p-trap. all the water from the pump and gutter was dumping right back at the house. of course I didn't discover the extent of it until I dug it all up. but sheesh! I replaced it all with 4" PVC that daylights 125' off the back of the house.

 

The height of the water will not change the AMOUNT of water that will be entering the pit. It will just start from a different height. You also loose the cushion that the added depth provides in the event of an extended power outage. Did you have a check valve installed on the exit pipe? I had a situation where a client's sump would pump water up into the pipe, only to have the whole of the water in the vertical portion pipe return to the pit and 5 minutes later it would cycle again to expel the same water. Creating a nasty cycle that never ended. The check valve will keep the water from back flowing into the pit. Also check that the discharge is carried far enough away so that the same water is not perking down to the same pit and creating another perpetual cycle.

 

hey czizzi i think we may have posted at the same time. the discharge is (now) emptied very far and downhill from the house. it was not previously. but we still have the high water table.

in terms of setting the switch on point at just above the water table level -- in doing so I would effectively stop pumping altogether (except for a rain event) whereas now the pump cycles every 45 sec. just moving the switch on point up to the bottom of the drain tile actually helps quite a bit -- here's why -- the bottom of the pit is filled with 2 large 3/4hp pumps that displace water and artificially raise the level, so having the switch down there reduces the amount of water that gets pumped out per cycle and makes it fill up again quickly. shifting the "switch zone" to above the pumps now all the vertical distance is water. cycle time is increased. further shifting it to the "tile zone" extends cycle time even more until it just stops pumping. but then you have a tile 1/2 full of water...

losing the extra 30-50 gals of cushion by keeping the tile partially submerged is an added risk to be sure. i need to think about that one. the pumps are quite powerful (storm pro BA75M), and are independently piped out of the house, so i'm reasonably confident they could respond quickly to any rush of incoming water. they are both powered by battery/inverter power supplies in case of power outage. total of 6 deep cycle batteries, 4kW of inverter power, and 9,000gph of pump capacity. so far i've never had more than 12-15 gals/min enter the pit, but you can never be too prepared....

 

Even though the pump is set to let the water go higher before it starts pumping, it is still supposed to almost empty out the pit before stopping.

Except during extremely large inrushes of water, the system works better with just one pump operating. Both pumps cycling on each time the water level rises high enough will empty out the pit so fast that both pumps stop while the drain pipes still have a lot of water remaining in them. (Excess water in the drain pipes will contiue to pour into the pit while the pump is stopped.) Ideally the pump should run slow enough that much of the water still sitting in the drain pipes will pour out iinto the pit while the pump is still working on the water in the pit. But the pump(s) have to be fast enough to handle any big inrush.

 

so I set the float switch to turn on at about 1/3 up the drain tile. the pump cycles every 4.5 minutes now, and pumps for about 12 seconds per cycle. this is much preferable to the 45sec cycles and 3 sec pump times I had before. as an added bonus the pumping is almost completely silent now due to the noise insulation of the water in the pit covering the pumps.

Allan - you mention the pit should be pumped dry each cycle. can I ask why? aside from longer pump runtimes, is there another reason? I am really liking keeping these pumps completely submerged. also I can't really think of a way to turn on at the tile and also pump the pit dry. that would require a switch with about 24" of travel - i don't think they exist?

as an aside, i've got 3 switches in the pit now. one float switch for the primary, set at 1/3 up the drain tile. a second float for the secondary pump, set just above the primary so it never turns on unless primary failure. and a 3rd pressure switch secured to the bottom of the primary pump that turns on with 7" of water (in the 34" deep pit) - this switch is not used now. but i'm going to leave it there so I can cut over to it before a heavy thunderstorm and keep the pit level low during the storm.....

 

Pumping the pit dry gives more volume for the next load of water to occupy and therefore a longer time before the pump starts again. The longer the rest period the better, even if the pump runs longer between rest periods.

Also, the difference between pumping the pit dry and leaving several inches of water behind means more time for additional water waiting in the drain pipes (if you started with the drain pipes partially submerged) to come out and become a part of the current load leaving yet more volume for the next load of water to occupy.

Cutting over to a third, lower level, start switch is unnecessary. With your setup, if the main pump cannot keep up then the water will rise above the main pump turn on level, hitting the second switch and starting the backup pump and both pumps will work together.

If you did cut over to a third, lower, turn on switch and the main pump could not keep up then the water will sooner or later rise up past the first switch to the second switch. Then you will need the help of the backup pump anyway.

They do make float switch assemblies that have a large spread (vertical distance) between turn on and turn off. If you needed to install one of these, then the original float switch that came with the pump would be bypassed.