Sump/sewage pump size for run-off ground water discharge questions.

[ShinDiors]

Newly found this forum and want to seek some insights on this water problem I've been trying to solve for our recently bought old house (built in 50s).

House we bought a year ago had this strange setup. In order to accommodate the addition of a 2-car garage and the sunroom above at the rear of original house, they extended/carved the driveway into the original backyard, and now the driveway is downward, with the end of it enclosed by the retaining walls. The only route that the run off water from the driveway, and from neighboring lot, backyard is a grated channel with a 4 inch PVC pipe buried under garage floor connected to a sump pit at the corner of the garage. Currently I have a liberty LE50 sewage pump in the pit, which goes 8400 gph at 5ft, but the discharge tube that connects to it is half inch smaller than the pump's 2 inch port. That tubing is partially buried into the cinder block wall then goes underneath/around the house to the street side drain. Pump is hooked up to the backup generator, so the power failure was not too much of a concern. Here is the problem:

The inlet 4inch PVC is at a rather low height of the pit, along with some foundation draintile inlets at similar height. When no rain, the pit is almost dry with not much underground water coming in, the pump is not running. When it rains the pump is cycling at reasonable frequency, if raining more heavily, the pump runs for 10s every 30s, until the incoming water start to back up in the pit and water level rises higher than the inlet pipe, that's when things start to go bad （happens once or twice a year). Water will then backed up at the grated channel and eventually enter the garage. I got some advise from drainage company that because of the water backed up inside the pit first, then backed up at the grated channel, it means that the bottle neck is the discharging capability rather than the inlet 4 inch pipe. What I need is to increase the discharge rate, so that the incoming water can flow freely (without backed up water in the pit blocking) into the pit.

I have got quite a few opinions, which are rather costly to me, from digging another pit at different location with another wiring and pump, to adding another pump in addition to my current setup and replace the entire discharging port with large pipes (including break through the cinder block wall to locate and replace the 1.5inch pipe goes out into the side backyard. A few concerns/questions I have in order to really pick a valid solution

1. From my description, do you feel that the problem is the discharging speed? I understand better solution is to reduce incoming water, for example, repair/waterproof the retaining wall to reduce he water from neighboring yard. My neighbor has already built a french drain system behind the retaining wall which helped a little, but I still see water pouring out from the retaining wall when it rains heavily. All my gutters were discharged through other pipes to the curb side and storm drain, and no visible overflow from the gutter (had guttergaurds) to the driveway run off.

2. How do I know if a pump is enough, for example, this 1/2 hp liberty pump has rate of 8400 GPH at 5ft, but the 1hp pump I got only has 7250 gph at 4ft. (curves from manufacturers attached), but requires much higher current/power than the 1/2 hp pump. The 1hp pump seems to have higher head according to the curves though. How do I compare this two pumps, if the max rate (speed at 0ft head)matters, does it mean that my 1hp pump is not as strong as 1/2 pump i have right now (because of different brands)? I ask this because it looks like the failure prone portion of most pumps are the float switch, I was planning to use a Hydrocheck H6000 high-lo electric switch with the pump until I noticed that the switch is rated at 13.8A while this 1hp pump is 14.2A rated (3/4 hp ones would draw less than 12A which can be used with this switch). I attached the current Liberty pump 's curve and the new pump I just got (circled out the 1hp and 3/4 hp ones). If 3/4hp is what I need, then I would couple it with the electric switch no problem.

3. Another advise is to reduce the 90degree turns in the discharging pipes and use 2 inch pipes until it is connected to the 4inch gutter discharge pipe that is buried and eventually goes to the storm drain curbside. My estimate is that there is not too much 1.5 inch tube after it goes out the wall and joint with the gutter pipe (have a rough idea where the exit from wall is but have not confirmed by digging), would it help my situation if I replace the exposed portion of 1.5inch pipe with 2 inch pipe without breaking the wall? Again I understand it is ideal to replace everything 1.5 inch before it's connected to the gutter drain, just coming from cost-effective angle.

4. If I put a more powerful pump in the pit (say the ihp pump listed above), how do I adjust the float switch to avoid over-cycling, especially when it only rains light to moderately heavy, which was handled alright with current pump) Should I let the pump turn on when water level is right below the inlet pipe since I notice that having water in the pit blocking the inlet seems to be reduce the inlet water speed quite a bit and cause water backup at the channel drain.
5. I'm restless about the pumping going bad for whatever reason, that's where the thoughts of more reliable non-moving electric switch came from. But other than that, do you think I need a secondary pump at all? Any other risk mitigation methods? Cheaper solution might be a utility pump with a flex tube either hooked up with the current discharge pipes somewhere or directly pump to street side? I will need to rewire another dedicated line from subpanel/backup generator for a 2nd pump too.

Sorry about such a lengthy post/repost, I'm trying the provide as complete information as possible for your suggestions. Thanks a lot

 

[Artisi]

Without getting into the nitty-gritty of your post, the problem is not the ground run-off but the massive amount of water from your roof drainage, worthwhile calculating what this is likely to be during heavy rain.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[ShinDiors]

@Artisi, thanks for your reply. I disagree that the roof drainage is the major factor in this as all my gutter downspouts are drained with underground pvc to the curb side, and all my gutter has gutterguard and I have not seen water backedup and overflow from the gutter in rainstorms.

I think the core of this problem here is as @LittleInch mentioned, wide range of flowrates that is difficult to be efficiently handled by one fixed rate pump, also the usable volume being not sufficient. Currently this 1/2hp pump is cycling on for 10-15s tops to empty the volume that sets it off (est to be less than 20gal, so little less than half of the sump pit). Upgrade the discharging pipe may be able to improve the 2-3 times surface flooding situation, but would not help the cycling time (probably would worsen it if the float switch not changed). Better solution is to increase the usable volume of the sump (either upgrade the current size or have a 2nd pit) with the discharging upgrade, that way the pump can be set at higher water level switch on so that it runs longer each time, in the same time the extra water flowing in (at extreme cases) will have some additional sump volume to stay before causing backed up at the garage door area.

cvg and LittleInch both suggested upgrading the discharging pipe first, and hope that could cope with the occasionally heavy rain storms. That could be the cheapest thing to start, and if that works, my next question would be how to safeguard this system coz it's a single pump (although backup generator protected). My thinking of the "two pump-one pit" is more as a safeguard plan for the primary pump failure rather than relying on the additional flow rate. As you can see, this is currently the only way any run off water could be discharged, if the pump craps out in a heavier rain storm, it's nerve wrecking to even think about.

If discharging pipe upsize alone is not sufficient or get me stuck at short cycle time (which increases the single pump failure possibility), then I would need a 2nd pit plus a pump. I'm weighing where to set up the 2nd pit.

a. 2nd pit adjacent to the current pit
Pros:
[ul]
[li]can utilize current set up for the inlet water, so far all the driveway and grated channel were grated in a way to divert water into this inlet pipe.[/li]
[li]maybe easier to wire up the 2nd pump[/li]
[li]can take the advantage of the same upgraded discharging capacity[/li]
[/ul]
Cons:
[ul]
[li]More difficult to dig the sump pit compared to operation in the open area.[/li]
[li]The only location of the 2nd pit would be in front of the current pit, and after that, there is not much room left, I'd think it would be ultra difficult to make any adjustment or maintenance especially for the original pit (currently if I need to do anything to the original pit, I need to ride on the square opening, one leg inside one leg out, no way for me to get my whole body inside and work on. I'm 5'11". If there is another pit in front, there will be no way for me at least to do anything with regard to the inside pit)[/li]
[/ul]

b. 2nd pit in the diagonal corner
Pros:
[ul]
[li]Easier to dig the pit[/li]
[li]Shorter discharging head loss (plan to pump straight up for maybe 8 ft and tap into the existing gutter drain pipe that is buried right outside the wall[/li]
[/ul]
Cons:
[ul]
[li]Need additional work or adjustment to divert the water into this pit (such as extending the grated channel etc). However this adjustment may helped my water damaged garage door posts problem, one stone two birds.[/li]
[li]Maybe more difficult to wire the power source (it's further away from my utility room)[/li]
[li]Additional cost if the original discharging pipes still need to be upsized.[/li]
[/ul]

I hope this summarize our discussion so far.

 

[hydtools]

Would a higher head capacity pump make sense to better push flow through existing plumbing?

Ted

 

[LittleInch]

You do also have a c which we haven't talked about much which is adding a second pump to the existing pit with a second pipe.

If you think this is an option then what I would do is swap out your existing pump for your smaller one using the same pipe.

Then suspend your bigger pump above the smaller one if you don't have room inside the pit for the two side by side but fit it to a new larger pipe. It should be pretty straight forward to core through that block wall and then out to the outside.

Then set the switch for the second pump higher than the first one by as much as you can, but at least 9 to 12".

You still might get some cycling when the flow gets too much for smaller pump, but overall the lower flow of the smaller pump should reduce cycling in more moderate rain conditions.

A bigger or second pit is better for sure but if it's just getting too hard / expensive then this is a viable alternative.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[ShinDiors]

@LittleInch, I'd think having to run another pipe out would be as expensive as swapping/rerun the existing pipe if not more (I think the new pipe would still be out from the similar height of old pipe and then connected to the same 4inch gutter drain that goes to storm drain right? or you were suggesting simply discharge out in the backyard). But worth asking when my General contractor comes. The stacking of two pumps scenario (but with Y into same upsized discharging) was the solution 1 with a quote ($3.6k). But your Option C here may re-purpose my 0.3hp zoeller (although it is a sump pump, not sure durability in getting this type of surface water) nicely, coz it has 1.5" discharge port matched the 1.5" pipes. But if the 2nd larger pump is triggered much higher, in the case of extreme incoming speed, the small one cannot cope with the speed, so water will rise up, covering the inlet and then the 2nd pump would kick in much later, by then wouldn't the water already fill the inlet pipe and causing backup at the grated channel? That has been my question all along, will the backup at channel happen if the pumps are triggered at level that's above the inlet pipe.

@miningman mentioned that the two pumps in series would not gain too much flowrate in the prior reply, but I guess that's when they discharge in the same pipe (not improving much even with a big 3" pipe?)

@hytools, swapping in an 1hp pump (the one I attached curve diagram) was originally my wishful thinking. As a matter of fact, it was a 1hp FQ sewage pump that was inside the pit when we had inspection (but not working). But it seems that this may cause worse short cycling if the sump pit only provides same 20ish gal to pump out.

 

[LittleInch]

"were you saying to have the 2nd pump with separate pipe （leave the existing discharge pipe as is) and discharge out on its own"

Yes.

Running different pumps in parallel into the same discharge pipe isn't a great idea.

Still easier than doing a load of digging.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[ShinDiors]

Sorry to repost, I was editing my reply while you were responding.

@LittleInch, I'd think having to run another pipe out would be as expensive as swapping/rerun the existing pipe if not more (I think the new pipe would still be out from the similar height of old pipe and then connected to the same 4inch gutter drain that goes to storm drain right? or you were suggesting simply discharge out in the backyard). But worth asking when my General contractor comes. The stacking of two pumps scenario (but with Y into same upsized discharging) was the solution 1 with a quote ($3.6k). But your Option C here may re-purpose my 0.3hp zoeller (although it is a sump pump, not sure durability in getting this type of surface water) nicely, coz it has 1.5" discharge port matched the 1.5" pipes. But if the 2nd larger pump is triggered much higher, in the case of extreme incoming speed, the small one cannot cope with the speed, so water will rise up, covering the inlet and then the 2nd pump would kick in much later, by then wouldn't the water already fill the inlet pipe and causing backup at the grated channel? That has been my question all along, will the backup at channel happen if the pumps are triggered at level that's above the inlet pipe.

@all, can anyone tell me
1. Is 10-15s on each cycle considered "short cycle"? What is the ideal on time and off time each cycle?
2. What is the normal float switch on water level? My gut feeling is it should not be far away from the inlet pipe level other wise water would backed up in the inlet pipe (basically the pipe itself become water-full)

 

[miningman]

Shindiors, I think you are focussed in the wrong areas. You are losing sight of the forest because of the trees. Almost everyone here recommends getting rid of the 1.5 inch pipe restriction..... only you can decide whether to go 3 or 4 inches. Forget about you spare 0.3 HP pump....... design a system you believe will work and procure the necessary hardware. You are an electrician.... the cost of getting power to another sump or pump must be trivial in the bigger picture. The cycling time of a pump can be designed/ accommodated when procurring the new pumps...probably a more expensive hi quality unit will give you what you need.

Given that previous owners have left you with a very poor design.. all rainwater flows back towards your garage door, I will reiterate that this may well become a $10-12,000 project, UNLESS....

I am not sure you have given adequate thought into intercepting rainfall before it hits the ground. Could you not install some kind of guttering low down on the retaining wall and divert the flow?? Have you considered re-locating the door to the house so the sill is about 8-12 inches higher than the garage floor.?? Is pouring an extra 3-4 inches of concrete on the garage floor worth thinking about?

And dont be too hard on your potential contractors. As the owner/client, it is up to you to determine what you want. They can advise, but do not reject their technical advice simply because it might cost more than your'd assumed

 

[Artisi]

ShinDiors:sorry missed the point on the roof drainage going to the kerb.

The comment from LI - if considering using 2 pumps for such a small sump - it is preferable to install 1 pump above the other.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[itsmoked]

A problem indeed.

Consider running a raised concrete lip down the driveway. There are countless high-tech concrete patching and machine-mounting high strength polymer based concretes that will stick like glue to clean existing concrete. Section off most of the driveway so only water that exceeds this new lip actually makes it into the current grate. Realizing that the water coming down the driveway is only a few millimeters deep the little curb doesn't need to be too high. Perhaps an inch?

Then where the little curb makes the deepest puddle due to your driveway grade, saw out the concrete for a LARGE sump, perhaps 36" or 48". This is out in the open so a conventional concrete saw can be used or even a skillsaw with a masonry blade if you're handy(desperate) and willing to trade hassle for labor costs.

In this design include where to get the power to run the new sump. The power can be a 3/4" pvc conduit cut in the concrete to the nearest garage wall where a transition onto the wall and regular conduit to the house supply happens, so include concrete sawing to encompass that.

Now you need to provide for the pumped out water. Saw the concrete for that exit. This time make it 3" pvc from the start. Sawing concrete outside, standing up, with sawing equipment, is nearly trivial as compared to the close corridors stuff being considered.

Leave the existing poorly done scheme to handle only what the added concrete gutter misses. Change nothing on it.

Grate/sump stuff is everywhere at any landscaping/sprinkler supply places. Concrete is cheap.

Don't waste your time trying to make the %#($& existing setup work right.

or get arty

Keith Cress
kcress -

http://www.flaminsystems.com

 

[LittleInch]

The issue over filling the inlet pipe isn't one which should bother you. If the inlet into the pit is covered there is no real impact to the flow capacity.

Only when the level in the pit equals the bottom of the inlet pipe in your grate will it start to back up. The only reason this isn't done is when the inlet is constantly submerged but stationary you can get some silting potential, but your max flows are such that they will sweep out anything. No need to be concerned.

So you can set the high trip / start point above the inlet level into the pit.

~So your questions
1 - 10-15 seconds for a 3-400 W motor may not be too bad, but motors like running, not starting and stopping. The start current is often 4-6 times what the running current is so frequent starts both heat up the motor and also stress it and the starter contacts which could reduce the life cycle. Difficult to be precise about this, but 10-15 seconds of operation every 30-60 seconds is just not a great design.

2) Up to you - normally set at a level which doesn't result in anything bad ( in your case the level reaching the bottom of the grate.

To test this just turn your pump off and slowly fill the pit from the gutter until you can just see water in the bottom of the grate / channel. then mark this level on the pit and adjust your float point accordingly to be just lower than this max level.

As to where you should or could run the new pipe - that is again in your hands - we can't really see where else you could go but you have a free hand to do whatever is cheapest and easiest. You don't have to follow the same route as the existing just so long as it goes somewhere and doesn't get much higher than ground level in the back yard.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[ShinDiors]

@all, thanks so much for all the great discussion. A lot to chew on for me. Will update once I have a clear pathway. Much appreciated it.

 

[LittleInch]

Yeh, been kind of fun.

TBH these forums are meant for larger industrial pumps and not "domestic" issues and we don't want too many, but it was sort of technical so you got away with it, plus lots of responses and pictures.

Hope to hear back about what you decided to do and if you have any more technical issues with your pumps or pump performance.

LI

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Artisi]

Think about a self-priming floor mounted pump located at a convenient spot to suit, this could be sized to suit the inflow - auto level controlled for on/off, although delivery pipe sizing could still be a problem.


It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[ShinDiors]

@LittleInch, just to update and a few more questions

We are going with the option C, so adding a separate 2inch discharging line and connect it to the Liberty LE51A, and repurpose the Zoeller M53 with the existing 1.5inch pipe (will remove some uncessary right angle turns).

I recently noticed that unlike what I estimated before, my current pump is trggered on about half way (definitely below the inlet pipe into the pit), so it only pumps out actually less than 20gal (maybe only 10gal) each cycle-on and it only runs for about 8-9s.

Now the 0.5hp liberty is raised about 5 inches from the bottom (sitting on two pieces of stones). whereas the 0.3 hp zoeller on bottom. How should I set up the float switch on the Liberty. The Zoeller is a vertical switch I think it would triggered on more and hopfully handle the moderate rain by itself. My question is if I should still set the liberty's float (even after it's raised up physically) at about the inlet pipe (with your filling water test) or I should leave it as is?

Thanks a lot.

 

[LittleInch]

Raise it as high as you can go ( the inlet pipe level sounds Ok to me)

Then as the rain flow increases and your smaller unit gradually operates continuously then you can still afford to leave the bigger unit as reserve.

As you note once it kicks in then it is likely to cycle quickly unless the flow really gets high, but you should maximise the running time.

I would also set the off switch at a higher (say 6") level than the smaller pump "off" level switch so that it keeps running all the time when the bigger unit kicks in.

As we've said many times this isn't a great system and really needs a bigger sump, but the longer the bigger pump can run for each time the better.

Hope it all works as we think it should!

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[1gibson]

Just throwing this out as a concept (skimmed the thread and didn't see it, maybe it was already mentioned) but you could get two flowrates with a single pump if you have a solenoid valve and two discharge pipes.

Single discharge for normal operation, would keep the pump left on the curve and flowrate down so you don't have really fast cycle times.

Add a "high high" level switch to the sump that opens a solenoid valve to a second discharge pipe for increased flow out, so the single pump would now discharge through two sets of pipes. Just tee it off as close to the pump discharge as possible and use the largest pipe that is feasible between pump discharge and the T (or Y, whatever fits.)

Do some quick match to see what friction loses you get with the existing pipe, maybe you want another discharge of the same size, or maybe it should be larger or smaller than what you currently have, depending on the pump curve.

Check "normal operation" (single discharge pipe) pump efficiency to see if it's acceptable, or if it will hurt your electrical bill.

This may or may not be easier than just adding another pump, but something to consider.

 

[ShinDiors]

@LittleInch. Actually went ahead dig out all the 1.5inch and now replaced it with 4inch pipe, so the two discharging pipes (1.5 and 2) now discharge into a 4 inch pipe underground.

Now the problem with the pit, since it is a trash can, my contractor did not find a good way to suspend the larger liberty too high up, so it was on two pieces of stepping stones (I'd say only raised about 3-4 inches from bottom), and because of the tighter space (now two pumps with two pipes), there is no way of extend the tethered float on the liberty pump without it bumping into other inlet pipes and stuff. We did a test with the max level of water (using the method you mentioned, fillng the pit until water backed up at the grated channel), the big pump alone ran about 10s until it stopped (where the small pump can still trigger on to continue pumping). However, I can't set the tethered float to that level without the risk of having it stuck/bumped into other stuff).

With the current trigger level, the big pump alone (we haven't tested two pumps together as we are figuring out the additional wiring with the 2nd pump) only ran 2s till it stops, which worries me, and it could be shorter had the two pumps were pumping at the same time. My guy could not come up with ways of raising the big pump higher, and the space is also a problem of having a long tether (so that the triggered on water level is higher).

We are hoping that we won't be seeing the two pumps on too frequently, but my back up plan is to bypass the liberty's tethered float and use those electroic hi-lo switch which does not run the risk of float being stuck. Before I go that route, any other ideas of setting up the bigger pump water level higher?

 

[LittleInch]

Shin diors

Ok, that's one way to do it.

Very difficult to add anything as these are all things you need to see with your own eyes, but have you looked at suspending the bigger pump on wires or cables from a couple of beams spanning the pit?

As to the float switch I can't see the issue so again can't offer much but I would do everything you can to increase the time the larger pump runs for so if it needs new floats or other activation switches then so be it and scrap the built in version.

1-2 seconds operation is no good at all.

Good luck.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[ShinDiors]

@all
Came back to do a final update and close it out.

To sum it up, we dug out all the 1.5 inch pipe in the backyard (about 15-18ft, just by me and my dad) and eventually located where it jointed with the 4inch pipe. We replaced all with 4 inch pipe. Inside, the existing 1.5 pipe was modified a little to reduce some right angle turns, and then the 0.3hp zoeller was repurposed as the main pump with the 1.5inch pipe, with the 0.5hp Liberty raised about 3-4 inches above as backup/2ndary pump with 2inch pipes separately. Two outlet pipes were connected to the new 4 inch pipe outside, in the backyard. Had to use Hi-Lo sensors for both pumps to optimize the run time, now the small pump run about 45-55s each time depending on incoming flowrate. I've only seen one time (about 3inch rain) when the small pump had to continuously run, but did not kick off the big pump (I was at home, so I manually turned on the big pump just to see how fast it can do the job). With the two pumps on, i'd say it's pretty beefy now at discharging water. So far with 2-3inch rain (max rate was about 0.5-1ch/hour), it seems that the small pump can handled it no problem. I'm not sure if this can handle the 4inch/hr rate we had last year, but should be alright for most of the scenes.

One thing regarding the hi-lo sensor, I recommend the hydrocheck sensor compared to the Chinese knock off brand Briidea. I made a mistake to use Briidea for the big pump since it had a higher current rating, however it did not take into the pump starting current pike into consideration, and would trigger the overcurrent mechanism which stopped my big pump when it's needed. The Hydrocheck one does not have this problem.

I want to thank you all for bearing with my "off-topic" thread here and giving me ideas/feedback. Much appreciated it.