Getting Your Pipe Fittings Right

white pipe fittings

Getting your pipe fittings right as a homeowner can be challenging. Of course, initially, you may feel that if you just put a SharkBite on everything, you're good, right?

If only Sharkbite made a drain fitting.... but I digress.

I mean, how hard can this plumbing thing be, said no homeowner ever, after the project was done. Lol.

So, in this article we are not going to be talking SharkBites or PEX and copper. That’s the water side. We are, however, going to be talking drainage. Or more specifically, sewer and effluent pipe.

I have been a plumbing inspector for a bit now, and I have a lot of homeowners in my inspection area. The most consistent violations are on drainpipe code applications.

Believe it or not, not every pipe fitting can be used everywhere.

short pipe fittings

Fitting Pipes Correctly

Most homeowners I deal with tried the “plumbers near me” option on the internet only to find the plumbers in their area were booked out for weeks, if not months. That's if they could even get them to return a phone call.

At this point, many homeowners figure they will have to do the plumbing themselves if it's ever going to get done, and if they're going to get the concrete truck on time.

Ever have to push out a concrete appointment? Don't do it. If you, as a homeowner, don't swear now, you will.

So off they go.

There are typically three types of homeowners.

1. Clueless

This type is very intelligent but wants it done by any means. They're just in a hurry and figure they can learn as they go.

2. Overconfident

This owner feels monkeys could plumb, and based on their work, they may have had monkeys do it. They are also very intelligent, but find plumbing code a hindrance and, although polite, grumble when they have to fix or change something

3. Inquisitive

This owner is also very intelligent but calls constantly because they want to pass their inspection the first time.

Notice a trend? They are all intelligent but react differently to their plumbing needs.

There is nothing wrong with any of these owners. What we are doing here is helping you to understand which type you may be so you can expedite your plumbing and your inspections.

What Code Does Your State Go By?

In my state of Idaho, we use a modified Uniform Plumbing Code (UPC), many other states use International Plumbing Code (IPC), and yet others use what’s called Boca Code.

Get on your state's professional licensing website to find out your state's code, or just call a local plumber in your area and ask.

Now, as I said, we will be covering drainage (which can be both black and grey water piping) pipe since this is where I find the most problems and violations.

Not Every Pipe Fitting Is Created Equal

pipe fittings fit together

Now whether you're using PVC pipe fittings or ABS pipe fittings, the rules are the same but beware of mixing pipe.

ABS glue cannot be used on PVC pipe nor vise versa. There is a specific glue used to transition between ABS and PVC. Make sure you know what’s allowed by code for those transitions in your state. Most codes will always allow a Fernco or no-hub band for transition between types of pipe.

As a side note—PVC, for instance, you must use glue and primer by code. If you have one-step glue that says it will also glue PVC, an inspector may fail those joints and make you re-glue them.

Doesn't happen often, but it can happen, and remember, we are here for your success, not your impatience.

The most famous violation is the difference between a Sanitary Tee (Santee) and a Plumbing Wye (Wye).

The pic below is a Sanitary tee commonly referred to as a Santee.

white T-shaped pipe fitting

A lot of people don’t realize that this fitting is primarily a vent fitting. What does this mean?

It means you cannot put it on its back in a horizontal drain run.

A Santee installed on its back can give the impression of a slight 45-degree angle, but if you look closely it's really just a tee. This can cause splash back into the tee area and is just not very functional as a drain in this position. Let's just say I have changed many so don't do it.

“Well Mike” you say, “what does that mean in English?” It means that many people think that if you put the middle up to vent the fixture (like above) that it's venting and not draining.

The problem with that is the fixture's primary use, on its back, is draining, and most codes don’t allow it. Doesn’t matter if you think they should or if you think it's silly. Your inspector will not pass it until it's changed.

Now a Santee can be used on its back when venting in the attic space, and it can accept a horizontal drain when the Santee is in a vertical position when accepting a trap arm from a sink.

This pic is a plumbing fixture wye.

y-shaped plumbing fixture

The plumbing fixture wye (commonly called a wye) can be used in both venting and drainage, but its primary function is drainage.

It can be placed on its back, side, or vertically.

So, what is the difference outside of its sleek racecar design?

I can personally tell you that when snaking a drain, I have had the cable go the wrong way up an improperly installed Santee but never a Wye.

The Wye has just enough direction to guide the cable, whereas the Santee only looks like it does with what you could call a "soft bend."

The next violation I come across is improper venting.

This Is Where Code Really Counts

brass pipe fittings

The code for your state will determine the size, quantity, and location of venting for your fixtures.

Most states allow a two-inch vent off the toilet that can also allow a sink, thus making it a wet vent.

Other states, such as Idaho, want a three-inch vent off the toilet drain when in a basement or main floor level so that a full-size cleanout can be added when it comes through the floor.

At that point, it can be reduced to two inches and still be used as a wet vent if needed.

Now why would Idaho do that? What would the advantage be?

Let me tell you how many toilets I’ve had to pull over the years for the purpose of drain cleaning because there wasn’t an available cleanout.

Pull the toilet.

Bring in the machine.

Clear the drain.

Take the machine out.

reset the toilet and hope the flange is good......

Maybe you get the point.

Side Note: A lot of people think, "Well Mike, isn't that wat you get paid for?"

Good question. Let me just say part of the reason I inspect now is because plumbing is hard on a body.

Another note on vents. They need to be rolled.

This means that when you put the wye in to vent the fixture, you need to roll the vent above what’s called the “center drain line.”

Really a good rule of thumb here is to make sure you know where you need to have cleanouts.

The Next Issue I Run Across Is Too Big a Pipe

What does this mean?

It means under IPC you can run a two-inch drain for a sink because they base their code off a combination waste and vent system), but under UPC (which is more of a every fixture needs its own vent system), you can only run a one-and-a-half-inch drain for a sink because you're only allowed to upsize one pipe size. Since the tailpiece on a sink is one-and-a-quarter inch, that explains it.

Another common venting mistake I run across is floor drains.

Once upon a time, in a place far, far away, you didn’t have to put a vent on a floor drain because its Fixture Unit Load was 0.

For whatever reason, that is the one thing most homeowners seem to remember, but unfortunately, that rule changed years ago. Floor drains do, in fact, need their own vent now.

I'll bet you're scratching your head now trying to figure out when floor drain vent changed because you thought the same thing.

Now I don’t expect you to remember everything we've gone over here, but I wouldn’t be much of a teacher if I didn’t cover it.

Keep in mind both codes have very good reasoning for their individual rules. They simply have different applications in different areas, and they change a bit every year.

Why, you ask?

Doesn’t really matter why. What matters is you pass inspection.

So, are we done yet?


Understanding Fixture Units

Each fixture has a unit load assigned to it, and every code has a table where you can find the unit load for each fixture.

Such as a toilet (water closet) has an FU (Fixture Unit) of 3, whereas most sinks (or lavs) have an FU of 1.5. This matters when you're figuring pipe size for your drains and vents.

A lot of codes want you to go out the foundation in four-inch pipe to ensure you have adequately covered your Fixture Unit Load for the house.

A good rule of thumb when figuring FU’s is full baths are about 6-8 FU’s depending on whether there is just a tub or a tub and a separate shower, or even if there is a double sink instead of a single


Single Lav (Sink)- 1.5

Shower- 2

Tub- 1.5

This also matters when figuring vent sizing as FU’s are assigned differently to each pipe size. for example, inch and half pipe can take 8 FU's, but a two-inch pipe can take 24 FU's.

These are just little things to remember that can and will help you conquer in the end!

Couple of Last-Minute Notes

Wrap your pipe when doing underground plumbing.

Typically, it doesn’t matter if you use duct tape or sill seal (that foam they use to seal the sill of the house), but the pipe does need protection from the concrete.

Also, make sure you understand the difference between a vent 90 and a drain 90. The vent 90 (the first one) will grab debris as its too sharp for drainage. Where the other has obvious flow.

pipe fittings fit together

Another thing to remember on plumbing Wyes: there are two on the market—one kind with a long sweeping arm, and another with a 45-degree fitting that you can swing in whatever direction you like.

One will hinder how much angle you can get (the sweep arm), and the other gives you flexibility. My only caution is to make sure you get the one that will work for you, not the one that looks the most simple. Remember the old rule. “Measure twice, cut once.”

Make sure you cut your pipe as straight as possible (which is more challenging than you might think) to give you a good seal.

This rule also applies when grabbing fittings. Think twice before you grab parts you may not need and hope the inspector will pass it with that fitting anyway.

There You Go

You’re not a plumbing expert, and maybe you never will be, but this should give you the edge you need to pass on the first try without feeling the need to call plumbing services to save you.

Lastly find out who your inspector is, contact them, and don’t be afraid to ask questions. Most inspectors are happy to help.

Keep in mind as well that Inspectors are judging Code, not Quality. Your Inspector is not expecting to see professional plumber-grade work when you only just picked up your first piece of pipe a month ago.

Good luck, and may the plumbing odds be ever in your favor.