Measuring relative heights of two points that are far away from each other is hard

March 15, 2009 12:52 PM

How can I figure out the difference in height between where my sump pump outlet sits at my house to where I want it to drain so I can assure gravity is helping it drain?

We just got a new sump system. This inside part works great, but the outside part not so much.

It currently dumps into the middle of the backyard, making about a 4' diameter swamp that the dog loves to play in. It also is leaking something fierce right outside the house. I've got the people who did the work coming in tomorrow to fix the house-side leak that is causing a huge puddle of water just outside the house, which just ends up draining back in and keeps the sump running. They are fixing this under warranty.

I don't expect them to kindly move the stupid outlet pipe to not be in the middle of the backyard under warranty. So I'm thinking about how to change this myself.

The sump pump does not pump the water down the outlet pipe. Instead, it just uses gravity. It comes up from the basement, out of the house and just drops straight down into the outlet (with little holes at the top so that if the outlet freezes, the pump can still pump up and out and onto the foundation directly). The only reason the outlet drains is because the house end is higher than the end that is in the middle of the yard (but not by much).

I'm thinking I can either just run it straight back to out behind the back fence (field behind the house) or I can take it out the side (we live on a corner) and down towards the sidewalk. Looking at it, it sure looks like the side is a lot more inclined than out the backyard.

But how can I find out for sure? If I take the time to dig up and move this stupid pipe, I want to be sure it works and drains, especially at the longer distance.

posted by cmm to home & garden (8 comments total)

Get a laser level with a bubble on it and get a big stick and stand at the two places. Raise the laser level until it hits the stick when it is placed at both locations and this will tell you which is higher or lower.

Basically, just like the surveyors do.
posted by Brockles at 1:03 PM on March 15

Well, if you have a long piece of clear tubing, you can fill it with water and the ends will find the same level no matter how far apart they are.

This would work with a garden hose as well, but you can't see inside so it can get tricky. If you attach some shorter lengths of clear tubing to either end of a garden hose you should be able to get what you want.

Measure down from the level of the water at both ends to determine how much of a slope you have.
posted by davey_darling at 1:07 PM on March 15 [1 favorite]

2nding davey_darling's use of a water level. Here's an illustrated, step-by-step method.
posted by webhund at 1:15 PM on March 15 [1 favorite]

The rather modest GPS unit I have indicates elevation down to the foot. I have no idea how accurate it is, but I have definitely seen it change as I go up and down a fairly modest slope.
posted by adipocere at 1:20 PM on March 15

Buy gutter material, like on the roof, and build a simple wood contraption that holds it and makes it slope downward, from the starting point, which is the exhaust tube of the pump, to the ending point, wherever that may be. by running the water above-ground, you can easily overcome obstacles such as dips and small hills in the elevation, by simply changing the height of the gutter at the starting point. kind of like the Roman aqueducts, but much simpler, using plywood and gutters. that's what i do anyway.
posted by metastability at 2:16 PM on March 15

Speaking of the roof, where does that water go? Does the pump develop enough lift to get the basement water to the same place, or up onto the roof?

If that just goes back to the pump suction in the basement, well, that won't work very well. Although it might make a nice water feature on one side of the house.
posted by ctmf at 2:28 PM on March 15

A water level will work but is actually over kill for what you are doing because you don't care what the difference is just which end is lower.

Get a garden hose long enough to span the distance. Fill it up with water by submerging it in a bucket and running water through it until there are no more bubbles. Using the assistance of another person each of you holds a thumb over one end of the hose. One of you holds their end at the outlet and the other at the desired destination of the water. You both release your thumbs at the same time and where ever the water runs out of the hose is the lowest point.
posted by Mitheral at 4:01 PM on March 15

I'll recommend this (only because I'm cheap and they're easy to use).

Stakes (1X2 furring strip made pointy at one end. One, say, two feet long the other, longer).
Big ball of twine (enough to go from where the swamp in the middle of your yard is to where you want the water to end up).
The above line-level.

Take one stake and stick it one foot into the ground where the outlet (in the middle of your yard) of your sump is. Tie one end of the twine to this stick, say three inches down. Extend the twine to one of the potential out-falls and clip the line-level to it. Mark how high 'level' is on the second stake. Go to the other location and repeat. Pick the outlet that is lowest (for which 'level' will be highest up the stake).

You could also talk to the guys doing the sump work, they might fix the other problem for minimal cost, recognizing that it isn't what you want and a happy customer is the best kind. Good Luck!
posted by From Bklyn at 2:46 AM on March 16