Commode won't drain

[sparkync]

I have a problem that only occurs periodically with one of the commodes in my house. I have a half bath with only a toilet and sink at the front of my house. I have another full bath approximately 35 ft. toward the back of the house. The bath at the back of the house is where it goes underground to the septic tank. This toilet nearest the septic tank flushes fine, but the one at the front of the house periodically stops up. Sometimes when the toilet nearest the septic tank is flushed, it causes the toilet in the front of the house to "burp" with back pressure (for lack of the correct expression ) It don't do this all the time. I replaced the toilet in the back bath a while back but have not replaced the one st the front yet. I'm wanting to make sure that is the problem before doing that. I thought maybe the problem was the vent stopped up in the "1/2 bath at the front of the house, so I went to the roof and stuck a pipe down the vent to make sure there was no bird's nest or anything in it. My pipe "bottomed out" at the bottom so I'm guessing it's alright. In your opinion, does it look like I need to replace the toilet itself?
Thanks for any help you can give me. Hope my explanation is clear enough. I'm an electrician and not a plumber

 

[Plumbs]

It sounds like you probably have some kind of obstruction in the drain. I just did a job with a very similar issue except they were on city sewer.
Ended up finding a 15 foot long belly in the line. The master bath toilet would flush fine but the one farther from the belly would bubble.

 

[Sponsor]

 

[sparkync]

Sorry to be so "ignorant", but what is a "15ft. long belly"? Remember, I'm only an electrician Sounds just like my toilet is doing though.
Thanks

 

[WorthFlorida]

It's the burp and why it happens with a good vent (presumably) is the issue? Is there a basement or crawl space below? If so is there a clean out? Check for slope and any dips in the main waste line. If there is no access below, you can remove the toilet and check the drainage. I would our buckets of water down the pipe and have someone flush the other toilet and check if you feel any air coming back or water?

The roof vent check may not have been all the way to the main horizontal waste line. The vent might be tee'd 42" above the floor to vent both toilet and sink. Place a garden hose down the vent pipe and let it run. When the problem occurs does the sink drain or does it drain slow?

 

[WorthFlorida]

With a dip (belly) in the horizontal waste line, it creates a trap because water lays in the pipe. No only cause drainage issues but will hold solids causing the occasional blockage.

 

[sparkync]

Just have a crawl space. I have old "cast iron" drain line going from one toilet to the other, then down in the ground. And yes the vent is going to the sink first, and if I remember correctly, when this happens, water running in the sink makes it "burp" also. ???

 

[Reach4]

How long since you had your septic tank pumped?

Much better early than late.