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BradH · Dec 12, 2006, 07:49 AM

I have a home with a walkout basement and a septic system. All the drains in the basement are gravity fed. The basement was plumbed for a bathroom with two 2" drains and a 4" drain. What information do you need from me to explain how to vent this setup? I believe that the drain that is setup for a shower is going to be used by two sinks and the drain setup for the sink isn't going to get used at all... it's only going to be a half bath. Now supposedly according to what I've read here the shower drain should have a P trap underneath the concrete but when I pour water into either of the 2" drains, the water all just drains away and I never see any standing water in the pipe. So I guess I have two questions here, How do I vent this bath and whats up with the shower drain not having a P trap?
The basement toilet flows out to the septic tank and I believe the rest of my houses two main 4" drains coming from each side of the house tie into this one.

Thanks,
Brad

cyberslider · Dec 12, 2006, 10:40 AM

A trap is just a drain pipe that is in a s shape so the water get stuck in the bottom of the S blocking any sewer gases from coming into the house. It could be anywhere on the sewer line before the septic systems. Some houses have just a main trap that does the whole house and all its drains and some houses have no main trap but one on each drain sink tub toilet shower etc. local building code tell how it should be done. So you may have a main trap system and you will not see water in the pipe. If you have no trap at all you certainly are going to smell sewer gas.

speedball1 · Dec 12, 2006, 11:15 AM

NOT SO cyberslider, BAD ADVICE!

"A trap is just a drain pipe that is in a s shape so the water get stuck in the bottom of the S blocking any sewer gases from coming into the house."

"S" traps are outlawed in the entire US and all of Canada. "P" traps are the traps that are mostly used in homes today.

All codes mandate a trap on eack fixture and that each frixture that's trapped MUST be vented.
You say, "Some houses have just a main trap that does the whole house."
This would under the heading of a running trap on the main that services the entire house. Again, OUTLAWED by all local, state and Universal Plumbing Codes. To have a house plumbed in that way would leave every fixture in the house with a direct connection to the house sewer with all the fixtures having sewer gas belching out of the drains every time something's drained or flushed.
NOT THE BEST ADVICE I'VE EVER SEEN ON THIS PAGE.
Sorry Cyber, I can't let a post such as yours go unanswered.

Brad, If you could post a picture it would help a lot. Hint: A stub-up for a lavatory wouldn't hold water but a stub-up for a shower MUST hold water or it's not trapped. Regards, Tom

BradH · Dec 12, 2006, 11:57 AM

I have attached a picture/drawing. I'll try to use the correct terminolgy here to describe everything else. I have two 4" stacks coming down on each side of the basement, one for the kitchen and the other for the bathrooms on the first level. I have two dry vents protruding from the roof (one on each side of the house). This basement bath was roughed in right in the center of the basement. Do I need to add a vent or tie into an existing vent or is there a way to do this without leaving the basement (AAV).

I'm not really concerned about the trap that "may" exist under the floor where I drained my sinks (lavatories - is that the correct term) unless this causes a problem. Right now the sinks are not vented, just capped off at the top.

The reason I ask this now is because I noticed lately that the water level in my toilet goes down to almost allowing an air gap but not quite. I filled up the bathtubs upstairs and then let them drain, I ran down stairs to see what was happening in the toilet but I couldn't see a noticeable drop in the water level. I did notice the water was "rocking" back and forth a bit in the toilet though.

I hope this helps.
Brad

speedball1 · Dec 13, 2006, 05:19 AM

Hi Brad,

For the two sinks you will raise 17 1/2" off the floor to the center of a 2" DWV cross and stub out either side to pick up the sinks. Off the top of the cross you will run a vent out the roof or revented back to a dry vent. If local codes allow you may install a AAV in place of the vent. You could have a blocked vent in the upstairs bathroom that's pulling the water out of your basement toilet but it's more likely that the drop in water's causing a vacume in the bowl. Good luck, Tom

BradH · Dec 13, 2006, 07:32 AM

Originally Posted by speedball1

but it's more likely that the drop in water's causing a vacume in the bowl.

Not sure if I'm reading this right. I'm assuming what you're saying here is that the water coming from the upstairs toilets is causing a vacume in the downstairs toilet... is that correct? If this is true, will adding the vent to the sinks in the basement bath relieve this problem? As it stands right now, this basement bathroom group is not vented and I want to correct it ASAP.

I talked to my wife's cousin last night (he's a local plumber) and he told me to add a Studor vent to each sink. I used a stacked configuration of sanitary tee's for the two sinks and capped off the stub out above that. I'm hoping that I can simply replace that cap with a Studor vent and that will fix this whole situation. Any input on this.

BTW. I read your public profile and greatly appreciate what you do here. After googling for answers about this plumbing situation and the first few results always bringing me back to this site I decided to register and ask my question. I'm new here and there seems to be a wealth of information on this site pertaining to just about everything. Anyway, keep up the good work.

Thanks,
Brad

speedball1 · Dec 13, 2006, 03:50 PM

"I'm assuming what you're saying here is that the water coming from the upstairs toilets is causing a vacume in the downstairs toilet...is that correct? If this is true, will adding the vent to the sinks in the basement bath relieve this problem?'
This will depend on where the lavatory drain ties into the toilets drain line.
Have you marked the bowl level at night and next morning checked to see if there isn't a crack in the bowl. Of course you can't discharge anything all night until you check the bowl level.

"I'm hoping that I can simply replace that cap with a Studor vent and that will fix this whole situation. Any input on this."
If local codes permit this will work.

"BTW. I read your public profile and greatly appreciate what you do here. After googling for answers about this plumbing situation and the first few results always bringing me back to this site I decided to register and ask my question. I'm new here and there seems to be a wealth of information on this site pertaining to just about everything. Anyway, keep up the good work."

Brad, we thank you for the nice words. We strive to give helpful advice to our members and hope to be rated the number one Q & A site.
Regards, Tom

BradH · Dec 14, 2006, 01:22 PM

I'm lost. I marked the water level after flushing the toilet right before I went to bed. My daughter woke up at 4:45am with the flu so I went down to check the level of the toilet... looks fine. Over the next few hours she was in and out of the upstairs bathtrooms quite a few times. Its now mid-day the following day after marking the water level. This means the toilets upstairs have been flushed a considerable amount of times, plus the showers ran twice now. The water level is about 1/8" - 1/4" lower than last night. But normally it would have been all the way down again... it's like a random problem. Toilet in basement hasn't been touched all night or day. I hate these types of problems because I obsess over them and they control my life until they're fixed... AARRGGHH! Got to get that AAV. I'll call the plumbing inspector to be sure they are approved. I'll keep you posted.

speedball1 · Dec 14, 2006, 04:45 PM

Well Brad,

At least we have eliminated a crack in the bowl or the vacume caused by flushing the upstairs john. Problems such as yours are solved by the process of elimination. Keep eyeballing the bowl level. Something, sometime will lower the level and when it does you've found your culprit. Regards, Tom

BradH · Dec 17, 2006, 08:25 PM

Well, hopefully I solved my problem today. I cut off the cap that I had on the stub up of the drain pipe and put an Oatey AAV on there. Had someone flush the upstairs toilet while I shined a flashlight in the AAV and watched the valve. The valve in there started jumping around so I'm hoping it will aleviate the problem. Only time will tell.

Brad

BradH · Dec 19, 2006, 09:10 AM

Well, that didn't work. I actually think it made it worse. I checked the toilet yesterday and the water was so far down there was an air gap and it happened in a short period (mid day - evening). It seems to happen after giving the kids a bath upstairs and then letting the water out of the tub. Any more ideas?

I can put another AAV on the unused drain and see what happens. I don't know how all these drain lines connect under the basement floor so I guess it may be a possible solution. Any comments on this?

Thanks for the help.
Brad

speedball1 · Dec 19, 2006, 06:32 PM

If draining the tub pulls water out of the basement toilet then the tub's not vented. Does it gurgle a bit when it drains? Cheers, Tom

BradH · Dec 19, 2006, 07:50 PM

I've never heard any gurgling coming from anywhere. I'll check out the vents up on the roof when I get time. Where would it be gurgling at?

speedball1 · Dec 20, 2006, 07:40 AM

It would gurgle in the lavatory trap if the vent were blocked. Have you considered adding a AAV just upstream from the toilet? This would dissipate any vacume caused by a discharge rushing past the toilet. There's no doubt in my mind the problem's caused by poor plumbing design. No reason for this, but it's my gut feeling. Perhaps venting the toilet's your best shot. Regards, Tom

BradH · Dec 20, 2006, 09:31 AM

Not what I wanted to hear. The problem is that it's impossible to vent the toilet. The toilet backs up to a cynder block wall and I'm not tearing apart my basement floor just to solve this. This house was built in 1999 why wouldn't the inspection have caught this? For now I capped off the sinks again and moved the AAV to the other drain. I haven't cemented any of the connections yet. I'll wait a couple more days and see what happens. Thanks for all the help. I'll report back in a few days.

Brad

BradH · Dec 20, 2006, 11:35 AM

Ok, I did a little more reading on similar issues here and it seems that basement showers and toilets are designed to wet vent through the lavatory vent. If this is the case, then moving the AAV to what I see as being the "planned" lavatory drain should fix this. As the way I see it, I hooked up two back-to-back sinks on what looks like the shower drain since it was plumbed out away from all the walls. The lavatory drain is right against the basement wall so that it would be hidden inside a finished wall. The way I designed my basement bath does not require use of this drain though. I have a hard time believing the plumbing in my basement is that screwy since it was built in 99'. I just wish I knew how all these pipes were connecting under the basement floor.