I have city sewer that is connected to a septic tank that the house flows into. The vent in my basement goes outside and is just a standard dryer vent with the flaps that open under pressure. I've noticed if we don't run the furnace or AC for a few days the basement starts smelling bad. The septic pipe is just connected to that dryer vent with dryer vent hose. and they didn't seal it up very well my question is can I just run a PVC pipe out through that hole with an elbow turn down at the end.

 

Typically a vent for plumbing is run through the roof of a house. I do not understand how a dryer vent would work for plumbing. A vent needs to let air in to help water flow down the pipe.

Perhaps some pictures are in order. What you have doesn't sound right at all.

 

A lot of that is either incorrect or done very wrong. Some pictures would be a big help.

1. I have never seen a septic tank discharge into a municipal sewer. All cities I've had experience with require the septic tank to be disconnected when the house is connected to the sewer.

2. The dryer exhaust is totally different and separate from the house's plumbing vent system. Plumbing vent lines can sometimes contain water so they are never run with flexible dryer hose.

3. Your furnace and air conditioning should not be drawing air from your basement and should not have an affect on smells in the basement.

 

It's very small town and every house has a tank that has a pipe that runs to the road I'm assuming. But I know every house has a tank. In the flex pipe there is a couple feet of pvc

 

You've got a bit of a mess there. I have no idea what someone was thinking with the dryer hose and that's not where you would locate a plumbing vent. You've probably got sewer gas leaking into the home. And, by your comments it sounds like your furnace or AC is drawing air from the basement which also isn't good.

 

Oh, my, lord! That has to be one of the biggest hack jobs I have seen.
I am not even sure why they would have put a vent there in the first place. Normally a vent would be near the fixtures like sinks and toilets.

I also think the cleanout should be straight out of the wall with the drain coming in from above with a wye to start.

I hope a plumbing pro will stop by. They will have better suggestions than I have.

 

On the suction side of of the furnace there is a big vent to let air in. It's a partially finished basement with air vents plumbed so you have heat and AC down there

 

Get this fixed ASAP sewer gas is not something to play with.
It can be toxic and also explosive.

I am not sure if you need a vent there.
With luck someone with experience with septic tanks will chime in.
Do you have a roof stack in the house.
Since you did not mention any problem with your drains/toilets you probably do but I would check it.
You may be able to just cap this off.

Also I do not see any glue on the right hand side of the dryer vent fitting, so it may not even be glued in on that side.

 

I'll probably just a solid PVC pipe off the t that's there and out the hole and put a turn down on it

 

To meet code the outlet of a plumbing vent must be at least 3' above any opening (window, vent...) or 10' away laterally. I would run the line through the rim joist to get outside then turn vertical and run up as high as needed. You don't need to have two 90's on the end. Because it's a plumbing vent water that rains in is no problem and it's less likely to become clogged with a birds nest.