How much slope is too much?

If you have drains that are giving you trouble, maybe they drain slowly or don’t clear out very well, you may have a problem with the slope of your pipes.

In plumbing, slope, or fall, refers to the angle at which pipes are installed. I know a lot of people think pipes need to be level, but they don’t. As we know, water flows downhill, so your pipes need to be angled to create the right amount of flow. This is a vital step in a plumbing system, and one a lot of people get wrong.

Now the standard you want in most jurisdictions is between 1/8 and 1/4 of an inch. Usually somewhere between there will keep things moving along nicely. It allows water to move fast enough to carry solids away.

If you have less slope than that, say 1/16 of an inch, that can lead to slow movement of water, which can cause solids to settle and eventually clog. The solids linger because the water isn’t moving fast enough to push them out.

Now why not then do more than 1/4 of an inch? Well then you’re going to have the opposite problem. The water is going to move too fast, leaving the solids behind. That can create blockages later on.

Now if you have access to the pipes under your house, this is an easy thing to measure. You want to get the right kind of level. A standard level isn’t going to give you precisely what you need. In my Amazon Affiliate Store, I have a plumbing level that has a pitch vial. It has measurements that can show you exactly what the slope of your pipes are. This can also come in handy if you’re trying to replace any pipes so you know you have it done correctly.

And if you’re not sure, or you can’t access your pipes directly, it’s always smart to call in a professional plumber.