The #1 DWV Plumbing Mistake (and how to prevent it).

Free Fitting Guide:

Learn how to prevent the most common DWV Plumbing Mistake.


Random Tube says:

I live in an apartment. For some reason the neighbors sewage backs up in our bathtub. Could this be the cause? Or what could it be?

Pete says:

Finally someone that knows WTF he is talking about

steve b says:

Bang a left when you get to the wall.

Jason Hamelin says:

That 90 fitting is wrong. You need two 45.

The Whole Truth and Nothing But says:

As a master plumber in Colorado and Washington I stand by this video. Thank you for giving folks this info.

Dan Swan says:

Kind of a no brainer.


As a union A card plumber I say let the journeyman run pipe and let the carpenter frame wood no one is gonna be a plumber by watching u tube . Just saying.

Cicliste C says:

Is this also true for vent lines? You can pretty much use anything to tee vent lines together, if I’m not mistaken

William Dean says:

oh my, santee on it’s side, noooo.

Cameron Brown says:

recently corrected plenty of these mistakes in a house a bought and currently doing a full house remodel. as well as added more venting. Before they decided that the waist pipe going from upstairs to down stairs needed more venting so they just drilled 3/4 inch holes on top of the pipe… you cant make that shit up. they tried to make the upstairs sink and shower drain uphill into the main which of course doesnt work. They used Ts instead of wyes or combos, used short radius 90s instead of long radius, ran to small diameter piping in places and went from 1 1/5 down to 1 1/4 from a banch to the main. found several joints incorrectly mated. decided glue was all it needed. lacked true supporting of piping which had sagged over time. a lot of which wasnt noticed until you removed the 3 foot of insulation off of it, or pulled the drywall to see it. Or well lack of drywall and more paneling. Even the domestic water was a mess, PVC main, switch to cpvc to copper back to cpvc, back to copper. ripped it all out except the main, added a true main shut off inside the house back at the point it comes out of the ground. I know some will boo and hiss, but i went with pex as a replacement. In union commercial construction anyway. Most of the guys were telling me why not copper, pex isnt real plumbing. I said The price. Im doing it out of pocket, copper is nice and i dont mind it when im not paying for it. but I couldnt justify using copper in my house do to the price. so I went with pex and used the copper crimp rings vs the stainless pinch ring. No shark bites, ive seen those fail to offend. I have used the caps for temporary while testing or getting some plumbing working to at least have running water. I was going to use a pex manifold but for this house i couldnt justify the cost of one. but none the less i did install isolation between upstairs and down stairs as well as a shut off before and after the water softener and water heater. Might be over kill but if something happens i want to have control quickly.

KelevraSXT says:

Not a plumber.. never will be.. don’t even know why I watched this.. but even I knew this. you’re telling me licensed plumbers fuck this up?

Frank James says:

This is especially the case in apartment buildings where clogs and buildups are far more inaccessible in many cases and a snake trying from horizontal drain trying to go down a T , is really frustrating ,even with a floating head on the snake why oh wye didn’t they figure this stuff out long ago

Jason Smith says:

Thanks for sharing this. Great information. As a plumber for 35 years, I tell inspectors all the time to call me if this line backs up so I can watch a maintenance man pull a ceiling cleanout plug for a stoppage on floor above. He responds and said “It’s the code” and I say “don’t forget to call me!” Lol

didier banegas says:

Without knowing I did the right thing in my house, thanks for the video.

Brad Wooten says:

Not suppose to use a sanitary tee on its side like that. It should only be used vertical

Alexaexander Ruiz says:

I don’t think a professional would do this mistake

Glasgow Prince says:

As a Master Plumber & Gas Furnace Installer in Scotland, I 100% approve of this video. It’s the same over here.

Armando Avila says:

No medium sweeps?

IlliniFanAtEIU1953 says:

I clicked on your link,, to try and get your free cheat sheet and when I entered my e-mail address as requested nothing happened. Were you forced to remove your cheat sheet?

Spurious Effect says:

I’m so glad that I live in an area that doesn’t have any building codes. No added expense, and no problems.

Xsiner says:

Cool never knew this.

bounchofbeaners says:

Ok but where is the p trap for sewer gas???
Lol nvm thats a toilet flange if thats a floor drain it needs a trap.

Kenton Squires says:

This is why I always call a pro for larger projects

Ruben Torres says:

Señor!! you the best!!

Dennis Smith says:
eric heine says:

A vertical line becomes a horizontal line when it is less than 45 degrees. A horizontal line becomes a vertical line when it exceeds 45 degrees.
Iron American Dream on YouTube.

Steven Morris says:

Both fittings shown in initial drawing are illegal in their respected positions according to UPC

Chad Simmons says:

any plumber caught cheating the public should be tied to a post..and given 50 lashes with a bull-whip!!!

Junk Yard says:

I’ve seen licensed plumbers that can’t even get lines roughed into the right places.

Averageskill says:

there are 2 wrong fittings in the picture

Stalk Stalkers INC says:

If you don’t know you can’t lay a tee flat and need a combination you are in trouble.

avelino chavarria says:

ty very much!

Johnny Casteel says:

People wonder when they need to get their main snaked every 6 months hahaha

deplorable infidel says:

good info on this issue, thanks

William Dean says:

Oh damn, I said that 7 months ago… lol

Possabilities United says:

Are these pipes safe to drink out of?

ArcolaBridge says:

When it gets the area where my septic main drain is in my basement smells like septic. Is mine main rooftop event freezing up? I live in Minnesota

Dewaltpro picture says:

Everything you’ve said is 100% correct. Absolutely No PVC nor Pex is Allowed in New York City. No Hub & Copper only for us

brandon phillips says:

You really know your shit….

StirCrazy says:

This is basic plumbing, waste doesn’t flow like water. Do it right and put in a clean out while you’re at it!

Moon Pie says:

I spotted the problem and ALL pros should have too and use the right fitting.
I only know because I’ve looked into doing by own basement bath. No reason anyone else should really know this though.

Matthew D'Andrea says:

The National Standard Plumbing Code used in New Jersey allows short pattern fittings to be used in horizontal to horizontal changes in direction. But only for individual fixtures.

onjoFilms says:

I didn’t put indoor plumbing in my house. I just shit in my neighbors yard at night. Problem solved.

Jonah Thoman says:

Amen Hammerpedia! I’ve been cleaning drains & sewers for over 30 years. You are dead on. Nothing more frustrating than a tee when there should be a combo or wye.
I recently cleared a bathtub line where the homeowner did his own plumbing. He said he couldn’t get the trap to line up with the tub drain, so he built a “360 degree loop” followed by a p-trap. My stomach sank. This was in the basement with a concrete floor.
Getting a 1/4″ cable through it was hell, but with lots of persistence I got the cable through and into the main sewer. The water drained great. There was just one problem………I opened the back flow prevention device (it was about 5 feet away) and I saw the cable in there. Problem was, there was no water coming through. Hmmm. That means the pipe broke under the concrete.
Sorry mister homeowner, but if you don’t know how to plumb, this can be the result.
Last I knew, he was jack hammering his basement floor.
Thanks for the video.

Roberto says:

I’ve got a vent 90 connecting horizontal to vertical and your outline says “NO”. Is that why i’m not getting a smooth flush and some scent occasionally backs up? Do you think I should first change to a long sweep before checking anything else since my outdoor vent seems good enough?

glenn graetz says:

Hello Dylan, My question is, Is it allowable to drain a toilet toward the front and have venting coming from behind?

SKMC69 says:

I can attest to this. I have a washing machine drain that spits almost every time into the floor. Some doofus installed a straight TEE in a crawl space….that is under a garage addition, so we can’t get to it until the whole thing is replaced and floor ripped up.

Pro Plumber says:

I am a plumber and I approve this video is correct. #plumber #plumbersydney

Fuentes says:

Spitz truth

President Evil says:

what is this modeling software called?

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