Dumb plumbing/vent question...

[Richard]

I understand that every plumbing drain is supposed to have a vent somewhere within 5 feet (or something like that)

Ok...find/dandy....

I'm just trying to better understand how the vent works (yes I've got a poor draining tub and the lack of a vent seems to be the logical reason why)

If you have a clothes washer and its pumping out water I can see how a vent would help because there might be no air coming into the system from the washer... meaning.... as the washer pumps water out, when it stops pumping it will otherwise create a vacume of sorts.... because no air can enter into the system... I think I've got that.

A tub is what is confusing me...

Seems to me that if you have a tub that is draining, not only can the water simply go down the drain but, there is nothing for the water to pull a vacume agains since the drain is exposed to the air in general.

Heck...the more I type, the poorer I think I'm asking my question....

If you have a hose connected to the house (washer analogy) and turn the spigot off, then the water will drain very poorly from the hose as the air has to come in from the END of the hose to allow the water to bypass it and work its way out. If you crack the hose open at the spigot and allow air to enter the hose then the water will drain out rather quickly.

I understand that logic.

Now...

If you attach the same hose on a "sink drain" that happens to be elevated 5 feet into the air (the sink is the bathtub) and remove any obstruction at the outlet side... the water will STILL quickly flow out of the sink, down the hose and out of it because there is nothing enclosing the sink to draw a vacume to fight the draining process.

Seems to me in the first picture you must have a vent but in the second picture you don't need a vent. By that logic, I ask...

Why would you EVER need a vent on a tub/shower drain??

I'm asking this in part because I know I do not have one, I've got a poorly draining tub and have been told I NEED a vent. You see my logic above and I don't really want to rip my walls & attic apart to install a vent to only not actually need one and still have a poorly draining tub.

How far off base am I?

 

[JB4310]

First off. I'm not a plumber, but this is what I think. You need tubs and sinks to be vented to allow for smoother drainage, without the vent it would be popping and gurgling as it tried to breath as it was draining out and it would drain slower. there is air in the house sewer but there's a gas trap in the tub/sink drain that doesn't let air through unless forced, that would create a vacuum.
Did yours always drain slow? How do you know you don't have a vent? I have slow draining tubs but it's due to hair, have to take them apart every few months, what a PITA,
John,

 

[tallyho8]

I am not a plumber and not skilled at plumbing but I will tell you a little I know about the situation from experience. One of my houses is not properly vented and the unvented drains gurgle much more than the vented drains. Also, when the unvented tub is draining it will pull a vacuum on my unvented sink drain and pull the water out of the trap allowing sewer gas to enter the home through the drain until you run more water into the sink.

Possibly, the vent helps the septic tank release pressure when the tub is drained into it.

A real plumber will probably answer your question more fully soon.

 

[Diesel-ME]

tallyho8 is right - an unvented drain can siphon the trap dry. You don't want that. Plus a poorly vented drain WILL collect more "crud".. you don't want that either.

~Paul (not a plumber either)

 

[B8FISH]

Can't answer the vent question (not a plumber either) but we keep a small piece of screen in the tub drain that is easy to pick up and pick off the hairs--much easier than taking the d**n thing apart every couple of weeks (can't believe my wife isn't bald with all the hair she loses!!). Oh, and it doesn't seem to impact draining speed (old shower/clawfoot tub combo) so gets used at least 2x day

 

[JB4310]

Can't answer the vent question (not a plumber either) but we keep a small piece of screen in the tub drain that is easy to pick up and pick off the hairs--much easier than taking the d**n thing apart every couple of weeks (can't believe my wife isn't bald with all the hair she loses!!). Oh, and it doesn't seem to impact draining speed (old shower/clawfoot tub combo) so gets used at least 2x day

Thank you, I'm going to do exactly that! was thinking about it, now I just need a nice little stainless steel screen.

 

[Richard]

Did yours always drain slow? How do you know you don't have a vent? I have slow draining tubs but it's due to hair, have to take them apart every few months, what a PITA,
John,

Wife says it did NOT drain slow when we first moved in. If it helps any facts to know this, then realize when we moved in, my septic tank was empty/dry as it was all new construction. (don't know if an empty septic tank would HELP a drain issue since it's got a big air pocket in it)

 

[ScottOkla]

So somewhere in this discussion is there an answer to why our kitchen area smells bad lately (like air from spetic system) when the heat pump in that area runs?

 

[tallyho8]

They may not have installed a trap on the drain line of the heat pump that runs into the sewer. If there is a trap, it may be getting sucked dry by a stoppage in the air vent or a vacuum caused by the blower especially if your air filter is dirty.

You may need to pour water into the drain line of the a/c because it does not drip water into it during the heat cycle and it also may have all evaporated since last time you used the cooling.

 

[tommu56]

Richard

I wish I had at least 1/8 the hair my wife cloggs the drain with on my head.

I found a thing at home depot
its called Zip it

Zip It Drain Cleaning Tool is Simply to Use & Unclogs Drains Fast

It works great only takes about 10 min to clean it with out disassembly.

tommu