Plumbing – Sump pump horizontal distance – Why do 90 deg angles put more load on the pump after a vertical drop

crawlspacedrainageplumbingwater

I'm installing a new sump pump basin in a new location in my crawl space. I currently have a Zoeller M53 1/3 HP. The discharge pipe will come out the back of my house, but I want to bring the discharge to daylight near a ditch at the front of my house. So basically, the pipe will need to do a 180 from the back of the house to the front. I can use 45s to lessen the load. Unfortunately, I can't have the discharge pipe come out of the foundation in the front of the house or the side given the basin location. I also want to hide the discharge coming out of the foundation in the back of my house and behind a bush.

The picture here shows how the discharge pipe comes out of my crawl space.

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From here, I'll need to use a 90 (or 2 45s) so the discharge goes from the back of my house to the side of my house. Then do the same so it goes out front. This will basically equate to 8 45 degree elbows and 1 90 degree elbow. There will be roughly 150' of horizontal pipe. Overall, this seems like quite a bit of load on the pump.

This picture explains what I mean. In the picture I'm just using 90s for visualization, but could use 45s if that would lessen the load on the pump.

enter image description here

My question is, why does the number of turns and horizontal distance after the downward 90 degree elbow (where the freeze guard is) matter? After the pipe enters the ground, the pipe will be sloped and gravity will help push the water to the end. It seems like after the pipe leaves the foundation of my house and goes downward, there shouldn't be any extra load on the pump.

Best Answer

As Jimmy Fix-it says, it's a question of whether the pump sees those elbows, and the associated pipe friction, or "dynamic head," or not.

If you have (say) a 2" discharge from the pump, but you put 3 or 4" pipe in the ground, then it's likely that the pump will never "see" the rest of the pipe, if it's properly sloped and does not freeze or clog.

If it's 2 inch pipe all the way, then it will fill up when the pump is running, and the pump will be pumping against that pipe friction. Whether or not that's a problem would depend on the pump specifications. Gravity flow with low head is quite slow compared to typical pumping rates.

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