My crawl space access is only 19" in height. This severely limits the sump basins I can find. Every basin I see that say that they are 18" diameter are referring to only the inside diameter. The outside diameter is 20-21" which won't fit (I tried everything I could to wiggle it through the door).
I've found a few smaller basins that are specifically meant for crawl spaces with limited access. However, I'm concerned that the sump pump will short cycle. For instance, the basin I'm looking at is only 14" inside diameter and 15" tall. So a pretty small basin. Most pumps at minimum recommend 18" diameter. I'm concerned that the smaller basin will be filling up too quickly.
Because I will mostly likely have to go with a smaller basin, I'm thinking of things I can do to help prevent the short cycling. I'm a visual learner and like to explain things visually, so just bear with me through some MS Paint!
If I have a basin that is 14" inside diameter and using a Zoeller M53 pump (already own it) that kicks on when the float switch is at 7", I'd have approximately 5 US gallons of water in the basin.
Getting a basin that is taller would do nothing for me. The pump will still kick on at 7" water height.
So a taller basin really won't help me much.
A wider basin is really what I'm after.
Going from a 14" diameter to 24" diameter will almost triple the amount of water. But unfortunately, I can't fit that in my crawl space.
Regardless of how I do it, I would backfill a few inches around the basin with gravel. However, I was thinking, what if I used large aggregate such as heart/fist size stone. I could put down normal gravel at bottom for the basin to sit on level. Then on the sides I could put the larger aggregate. I'd also have a permeable non-woven geotextile fabric to separate the aggregate from the soil. Lastly, there will be a vapor barrier that goes over all of this and tucks into the basin and is sealed with a good cover. The advantage with this is that I could hold more water with a wider hole and using larger stones.
Is this a practical solution? My Zoeller M53 pump seems too powerful for the 14"x16" basin with only 5 gallons before it kicks on. Therefore, I'm trying to solution a way to increase the amount of water it holds. Should I instead buy a smaller less powerful pump? I was hoping to be able to save money and reuse my current pump. It needs to be able to go about ~5 feet and over ~5 feet before it exits the crawl space and into a freeze guard. From there, it travels ~110 feet.
Best Answer
Your "basin" need not be sold as a "basin" - the good old fashioned, fits very easily through limited access, pile of bricks or blocks that you use to line a hole that you dig (of whatever size you like, since you assemble the wall in place) will solve your diameter problem.
The other obvious solution would be a different pump with an adjustable float, or a secondary float switch for the pump you have that would prevent it from turning on at 7" when set in a deeper basin.
If you are dedicated to pre-manufactured sump basins, install several of them in close proximity connected by 3" or 4" pipes. The large aggregate you propose will fill much of the void space you propose to add - if you are digging that much hole, line it with bricks to get most of the storage capacity from the large hole (or use multiple connected basins.)