# any plumbers out there? septic help



## dvellone (Mar 17, 2012)

I've got perplexing issue that I can't figure out.

I'm on a septic system -1k tank and evaporation field of 2) 60' runs. The system is 7 years old. Tank was pumped out last Spring and at the time of pumping was in very good shape -no over accumulation of sludge layer.

My vents are all installed as per plumbing codes and the system has worked perfectly until this latest issue.

What's happening is, when I flush the toilet everything flushes down just fine but just after the bowl clears I get a blow back, a small reverse pressure blast. Also, when the clothes washer is draining (which is in the bathroom and before the toilet) I get the same reverse pressure which, since the bowl is full of water now is a bubbling or gurgling in the bowl. No back ups and everything drains well otherwise.

I pulled my septic tank cover and my inlet is clear of any obstructions. My vents are all working fine and I have blockages in my sewer line.

I do have back-pressure valves on my vents to prevent septic gasses, but I've had them in place since the beginning and everything has been fine till now.

I can stop the problem by taking the cover off of my outside cleanout. When I remove it while the washer is draining or toilet flushing I get a blast of air releasing.


----------



## basod (Mar 17, 2012)

sounds like the vent line from this drain run is blocked. The air the drain has to have somewhere to go when toilet is flushed, and when the water leaves the vaccumm void is then filled via the vent.
If you can access it in the attic, make sure there isn't anything common running into it like a bathroom vent fan, and any bow(horizontal leg) in the vent can create a water loop that will cause the same issues your seeing.


----------



## smoke show (Mar 17, 2012)

I have had similar concerns and it was indeed a plugged vent.

I could not see any visible obstructions looking into it with a flashlight.

Went up on the roof with the garden hose and flushed it out.

Edit- I'm not sure what basod means by checking in the attic. My plumbing vent penetrates the roof.


----------



## greg13 (Mar 17, 2012)

It's a vent issue somewhere. It may even be outside at the tank.


----------



## dvellone (Mar 17, 2012)

This is what's perplexing... the vents are all free and clear and are functioning well. I'm not losing trap water seals, and my drains have no negative pressure - they flow out well. Instead there is positive pressure. I do have vent valves on both my stacks and they prevent any positive pressure from escaping, but I've had these in place for about 5 years with no issue at all. I can remove one of the valves and the problem is instantly solved and I guess that's what I'll do, but why was I able to get away with the valves for so long with no positive pressure issues till now? Wondering if anything else may be at play. Thanks.


----------



## nate379 (Mar 17, 2012)

If your vents only allow air to come in where is the air going that needs to be displaced when water goes in the septic tank?... sounds like that is part of the problem.


----------



## smoke show (Mar 17, 2012)

nate379 said:


> If your vents only allow air to come in where is the air going that needs to be displaced when water goes in the septic tank?... sounds like that is part of the problem.


 out the tank vent.


----------



## greg13 (Mar 17, 2012)

Those type of check / vents are very common in Mobile homes, they do go bad with the same symptoms.


----------



## nate379 (Mar 18, 2012)

The actual tank has a vent? I haven't seen that before. The only vent that normal septics have in this area is the one or two coming out of the roof. Maybe cause a vent like that would cause the tank to freeze solid? Even the vents on the roof can freeze up when it's cold.

I would imagine you always have a sewer smells coming off that... at ground level?


----------



## smoke show (Mar 18, 2012)

My bad. Its not a vent, its capped must be inspection only.

My system has the vent penetrating the roof and one at the end of the leach bed.


----------



## Ehouse (Mar 18, 2012)

It sounds like you have AAV's (air admittance valves) instead of an actual vent out the roof or side wall.  In jurisdictions where these are allowed you must have at least one properly sized vent to daylight to prevent just the problems you are experiencing.  You either have a blockage or insufficient venting to daylight.  If things function properly when you remove one of the AAV's, try a new one in it's place.  You may have too many fixtures with AAV's even if your main stack is vented to daylight.  If you have a main vent, what size pipe is it?  You could also have improperly installed venting.  There are spacing requirements for different size pipe and number and type of fixtures.

Ehouse


----------



## basod (Mar 18, 2012)

smoke show said:


> Edit- I'm not sure what basod means by checking in the attic. My plumbing vent penetrates the roof.


 
Not saying they don't vent to the roof.  They may not in this case if these are AAV's as Ehouse noted above
If there are any common lines, like bathroom vent fans that attach to the same vent, they can collect condensate in a cool attic. Causes a loop seal and creates this exact same condition.


----------



## greg13 (Mar 18, 2012)

I have seen many ground vents at the tank here, it may be a regional thing.


----------



## dvellone (Mar 18, 2012)

Ehouse said:


> It sounds like you have AAV's (air admittance valves) instead of an actual vent out the roof or side wall. In jurisdictions where these are allowed you must have at least one properly sized vent to daylight to prevent just the problems you are experiencing. You either have a blockage or insufficient venting to daylight. If things function properly when you remove one of the AAV's, try a new one in it's place. You may have too many fixtures with AAV's even if your main stack is vented to daylight. If you have a main vent, what size pipe is it? You could also have improperly installed venting. There are spacing requirements for different size pipe and number and type of fixtures.
> 
> Ehouse


 
That's right, I just have AVV's. My system is tiny and vents are all sized and located as per plumbing codes, but I put an AAV on my main stack about 5 years ago in the Winter when I got tired of of the sewer odor on the very cold evenings when falling air brought them to ground level.

My drains continued to function perfectly so I just left the valve on. Now, 5 years later I'm finally seeing the positive pressure that I'd think should have occurred shortly after installing the AVV's.

I've taken the valve off the main stack and eliminated the positive pressure problem, and though I may be risking sounding like a moron, I'm stumped over why this problem didn't occur for 5 years? Where was the pressure going, and could it's presence now after not happening for so long indicate something else going on with my system? I meticulously plumbed my home, and installed my septic system and try to stay ahead of any problems to avoid what would be a disastrous shutdown for my wife and girls.


----------



## basod (Mar 18, 2012)

Having an AAV in the main stack vent would bottle the system, and I'm curious how it would have allowed the waste water to enter the system so freely in the past.
In the past the water entered the system and probably had free room to "level" out and provide an air gap, you could have sludge building in the drain that doesn't provide enough room for the water to break the air gap, might possibly be roots in the drain joints.  Either way I don't think you can put an AAV on the main stack vent, it'll effectively eliminate anywhere for the sewer gas to go and pressurize your entire drain system.


----------



## basod (Mar 18, 2012)

And one more thing to consider - you said daughters and wife.
They have gotten older in the past five years - hair/leg shaving creams, and feminine hygienge products wreak havoc on septic tanks/drain lines


----------



## JustWood (Mar 18, 2012)

Is the inlet pipe underwater in the tank?


----------



## Morgan (Mar 18, 2012)

You should have one continuous 3" vent from your septic tank to out through your roof with no restriction allow your septic tank and plumbing system to breath (vent).  If you have any normally closed back water valves installed preventing this venting from happening then that is your problem.  Normally closed back water valves are to protect basement fixtures from upstairs fixtures in case of line blockages.  If you must protect your house from the septic field from backing up then you should use a normally open back water valve.

You mention in your original post you have back water valves installed to protect your vents..  ...are you talking air admittance valves?  Do you have a 3" or 4" stack penetrating your roof?  If so try to following this line down through your basement and out to your tank, if there is any normally closed backwater valves installed on this line, open them up and remove the flapper.  If you feel you need back flow protection on the run, install a normally open backwater valve.


----------



## dvellone (Mar 18, 2012)

LEES WOOD-CO said:


> Is the inlet pipe underwater in the tank?


 
It is, but the pitched sewer line terminates at a tee the bottom of which continues down to the lower part of the tank. The tee is free from any obstructions as is the entirety of the sewer line so I'm assuming that the pressure build up is not caused by an obstruction but just the closed system. Even with the pressure the drains worked fine, except for the "burping" toilet which I've stopped by removing the AVV from the main stack. Everything is whistle-clean and the tank which I had pumped out last Spring was in very good shape at the time of pumping and is fine now as well.


----------

