We live in Mexico.

We have a 'septic system' which has chambers. I'm not sure what you would call the first - perhaps collection. Then there are fermentation and oxidation chambers (based on the schematics we received with the house). Hopefully this sort of design is universal for septic systems. I think we have a septic 'farm'.

So every year when it starts to rain (and we are talking heavy rains) the main bathroom starts to smell. So anticipating that we started digging up the septic system today. After eight hours work we have uncovered what would appear to be the oxidation chamber. It is about 12 feet deep - and bone dry.

Would you EVER expect to see any 'water' in that chamber ?

Tomorrow we will follow the PVC and try to uncover the other chambers. At this point I'm a little worried that our 40 foot tall avocado tree has some roots which have gotten into the plumbing...

 

Typ there is a single tank that is divided into 2 sections.

The first section collects and contains the solid material for breakdown and the second section allows water to flow out to the field.

So when you state you have located a tank that is dry something's not right, possibly an abandoned tank?

 

ihp-

I just have an old standard anaerobic septic tank but as Marq1 mentioned most have just 2 chambers.

But I believe an aerobic septic system has an aeration chamber – or oxidation chamber – into which air is pumped and mixes with the wastewater. I believe you should have a pump somewhere which pumps air into the aeration chamber if that is the type of system you have and you should see piping that somehow would allow the pumped air to enter the chamber. I do not think you should see a bone dry tank if that is in fact an oxidation chamber.

Maybe you uncovered an abandoned tank as Marq1 suggests.

But I’m no expert – to say the least.

 

We continue to dig up our backyard. At this point it looks a little like an archaeological site. So far we have only found one large tank which is 12 feet deep and perfectly dry. We have found two pipes leading to that tank (one for black water (upstairs) the other for clear water (downstairs)). There should be a couple more pipes yet. The large tank we uncovered does have a ventilation tube at the top.

I have come to feel that the schematics we were given when we bought the house 4 years ago are total BS. I'm coming to think that we don't have chambers in our 'septic' system - just the one we found. Supposedly we are supposed to have a series of 'registers' which is what you would typically clean out as part of maintenance. We haven't found those yet either. Gosh I wish I had access to a Bobcat...

We have been in this house for going on four years. True there are only two of us but we do use the bathroom with toilet paper etc. All that stuff has to be going somewhere. If our weather were like today (dry) year round this wouldn't even be an issue - but we are about to enter rainy season and that brings really bad odors to the master bath.

 

Can you find someone with a camera snake? It may be worth some money to get them to camera out the lines and see what you're dealing with - at least to the first tank. Many camera snakes can also locate. Will definitely save some digging.

It may be too late, but I figured I'd suggest it. Can't help too much with the septic side though.

 

Still digging... (I quit today after 4 hours - I'm 62 - but we have a 22 year old continuing the digging). We have isolated the 'black' water line out of the MB toilet. That is really the principal area of concern. I actually heard the water flowing down the 4" PVC tube. The PVC seems like very poor quality and in fact is no longer round. In one place we found, near a coupling, that the top of PVC tube was even broken. At some point I suspect it will tie into the black line from the second story. We are almost to the point where such a junction would occur.

As I write this I am thinking that the 12 foot deep cavern we uncovered might be an old well of sorts. It is just that there is an aeration tube leading away from it.

The realtor who sold us this house (four years ago) has a brother who is an engineer and he has agreed to stop by tomorrow morning to offer his 2 cents.

 

Maybe this separate tank was a dry well for handling your relatively clean "gray water" from a wash machine or from the showers and bath tubs as opposed to effluent from the toilets or the kitchen sink which may contain decomposing garbage ?

 

Still digging - but making some progress. While following the path of the 'black' water pipe we just passed underneath the 'clear' water pipe (which actually jives with the schematic dated 2007). At some point we should hit a 'register' - which if memory serves there was something similar even in our house in Florida where rotter router or such would clear out the clogged line.

 

I'm repeating myself saying: I’m no expert. But I didn’t think anyone would put a septic tank(s) 12 feet below grade. I thought you normally have a ¼ inch drop per foot in the piping so that everything drains downhill properly – but no way would the tank(s) need to be 12 feet down.

But I certainly can be wrong about that!

 

Can't edit the last post, I just see garbage but -

you said the chamber was 12 feet deep, not down 12 feet. sorry - my bad!!!

 

Still digging - but making progress - we have found a plastic tank which I'm guessing is our septic tank. It is perhaps 4 feet deep with sludge (doesn't smell as bad as I would have thought). Whatever outlets (inlets for that matter) seem to be below sludge level. So for whatever reason the tank does not appear to be draining. (Is the outlet near the top of such a tank or the bottom). We are trying to contact a service which would pump out the tank so we can get a better idea of where the plumbing comes from/goes to.

 

Top . . . . with some kind of baffle to keep floating debris from exiting.

 

Thanks - so then if this were a 'normal' system would it end at the plastic tank or would you expect to find an 'oxidation' chamber further along ? (Our engineer canceled on us today).

 

A normal system (in my book) is along the lines of what Zoesdad described on the 10th as his own.

A normal system would allow the effluent to partially decompose within the tank and as it is liquified, it is allowed to exit to either a distribution box or directly to a leach field . . . . so "NO"; it would not end at the plastic tank.

Here's a decent write-up on the most common types of septic systems in the US; and I think these also prevail in Mexico:

Septic Solutions - Installation

Here's a visual of what happens in a "normal" septic tank; but we really don't know what the design of your system is yet:



Some kind of enhanced oxidation or aerobic septic system sounds like it would be more expensive than a conventional system . . . . and you'd have to expect that this additional cost was incurred for a reason having to do with the lot size or your local environmental conditions.

Even south of the Border, people don't normally deviate from the conventional for no reason ?

 

Well we had the suction truck come by a little while ago. Cost 3000 pesos (about 160 USD). took them an hour but they did a very good job and the septic tank was spotless when they were done. We also exposed most all of the 4" PVC from the house to the septic tank - about 10 meters (33 feet). There is a short section we have not yet uncovered and I'm afraid we may have to lose a very productive lime tree to get to it. While they were pumping out the septic I forced the master bath toilet to free flow. When I went outside none of the water was making it to the septic tank but just leaked out the holes in the cheapo PVC.

So first task Monday is to replace the 33 feet of PVC and see if water is kind of entering the septic tank like you would expect. Then uncover the last bit of PVC into the septic tank and maybe start to look at what happens to the waste after the septic.

Even after clearing out the septic and forcing water out the exhaust - no water was entering the mystery 12 ft deep chamber. But perhaps the PVC between the two is crushed as well.

 

Maybe that "very productive lime tree" has sent its roots into the leach field piping ?

 

It could be the lime tree, or the guava, or the grapefruit, or the plum, or the orange etc.

But after seeing the other PVC leading to the septic tank I'd bet the cheapo PVC is flat as a pancake.

This experience kind of reminds me of when we were living in the States and had to open the wall behind the washing machine (in the garage). There was a lot of 'ugly' stuff inside that wall.

 

Ok so KEEP the tree and route the new 4" pipe around it (maintain 1/8" per foot pitch). An additional 10-20' of pipe costs almost nothing - it's well worth keeping the tree!

 

Cheap or expensive, Leach Fields are not supposed to be driven over by anything heavier than a lawnmower . . . . but that general rule is hard to impose if you don't know where the Leach Field is.

It sounds like someone may have been tempted to plant an entire fruit orchard right over the lucrative and nutrient rich absorption area without considering how invasive the roots of those trees might be ?

How large is the parcel of land that your residence sits on ?

 

And since you might be installing a new drain line it's a good time to install a clean out or two. I like to put one where the line exits the house. They make special cleanout T fittings but they can be hard to find but putting two sanitary T back to back with two vertical risers works. That way you can rod, snake or auger into the house and out to the septic tank in case you have any clogs in the future.

 

I really don't know how big the lot is - off the top of my head maybe something like 200 X 100 - but it has a swimming pool in one corner and a lot of trees on one side - maybe as maybe as 20 trees (they are close together). It would be very difficult to get anything other than a lawn mower to the area of the septic tank.

The schematic has at least four traps (they call them registers here) but we still have not found a single one. The house is about 20 years old. Plastic septic tanks were not used back the, only in the last 8-10 years. So a previous owner had a problem at one point. When we opened the septic yesterday there was no toilet paper - so the thought is maybe the paper is getting caught up in a trap somewhere. One trap is supposed to be where two 'black' water lines come together (the master bath and another line which comes around the other side of the house) - right next to the septic tank. The septic tank is not on the schematic.

Actually - the 30+ long line coming out of the master bath runs past the septic tank and may run under the lime tree I mentioned. The schematic says there is a trap there. About a year ago we had a particularly windy night and the lime tree was uprooted. Since then I had it tied into a nearby wall so maybe I could just push it over to get underneath it.

If there is a bright spot in this story at least labor is relatively cheap ...

 

One bright spot is that you apparently have no municipal or regulatory agency in Mexico looking over your shoulder to observe every move . . . . on less than ½ an Acre you'd have sever obstacles to overcome with Regulations here in the States.

Is your lot serviced by a municipal water system, or do you have an on-site water source in addition to on-site waste water disposal ?

 

We have a community well - which is good and bad. They only have water available at the street about half the time - to give the pump etc a rest :-) The water is MUCH cheaper than we were paying in the States - which with the garbage pickup and waster water were like over a hundred dollars a month.

We have not seen any sign of permitting etc - but they have some strict rules sometimes. You are not supposed to cut down a tree without getting permission (steep files apply if you do). But we are kind of out in the boonies and a neighbor would have to report us (which did happen to one neighbor of ours). The other thing they are really tough about is making sure that the run-off water makes its way back into the aquifer. When it rains here it pours and we used to have a lake in the street in front of our house. So the community offered to run an 18" pipe on the outside wall of our property. They really had to come up with an elaborate solution to get approval.

 

These weekends - even in 'retirement' - are too short. I hate visiting Home Depot here because they really charge a premium (guess it is a dollar/peso thing). But we did today - to pick up joints,glue etc. We will buy the PVC tubes closer to home tomorrow.

In terms of traps - I picked up a 4" tee and a 4" cap. Given that perhaps I can fashion something that will work (Neither of us have all that many years left to worry about it). I won't glue the cap but maybe I'll put a screw through it to make sure it stays in place.

You guys in the US really have a shopper's paradise. In many ways.

 

Still digging - but making a lot of progress...

We found a register - kind of like a trap in the US - but it is perhaps 2 feet square concrete. It was directly underneath the lime tree. Fortunately our gardener (and his two people team) came by late today and we managed to move the lime tree to a new location. Fingers crossed on that. We also had to move a (much smaller) plum tree.

Earlier we pulled the toilet in the MB and tried to snake it out to the garden. That didn't work so well but the plumber sent a piece of looped wire down the toilet line and from the garden side was able to hook it. So we are assuming there is no trap there - which is good because it would have been behind a newly build exterior wall.

So we put in the new tee trap near the house and ran the new 4" tube out to the lime tree register.

The newly cleaned out septic tank had some new contents today but I'm not sure that was due to 'usage' or rain and the porous PVC tubes.

BUT - the most interesting discovery today was that we have ANOTHER (1100 liter) plastic septic tank ! At this point it would seem that they are kind of daisy chained. So perhaps the person who dreamed this up saw the first plastic tank as fermentation and the second tank as oxidation. Don't know yet.

 

We are getting there. We isolated the real problem in our system. The register (trap) was almost empty. The first 1100 liter tank (I'll call that sludge tank) had a three foot length of 4" PVC leading to the second 1100 liter tank (I'll call that the fermentation tank). BUT - that PVC tube no longer joined the two tanks. When we started this project both of those tanks were filled because the waste wasn't flowing any longer. I have no idea how long that was the case (a little scary). The third tank (the oxidation cavern) hadn't seen any new content in a long time - and was bone dry.

Here's a question. It is just my wife and myself. Today the sludge tank is virtually empty and it will take a long time for us to fill it (1100 liters) to the point that anything will flow to the fermentation tank. Are we better off leaving that first tank empty or should I use the garden hose to fill it so the system is 'primed' ?

 

I've been wondering why you've had so little response from this Forum in discussing your plight (I've never heard of a waste disposal system quite like what you've been describing) and I've concluded that your initial post should have been placed in Wells, Sump Pumps and Septic Sewage Systems . . . . and I'm asking the Moderators to move this Thread to that location so that you'll get more input.

 

Moved as requested...............

 

When you finally found the septic tank first chamber it was quite full of sludge and also the waste water from the house was not all getting there due to holes in the pipe along the way from the house.

The first chamber should be about 85% full all of the time, which usually means the liquid is about a foot below the top. The tank should be pumped every few years so sludge does not get more than about 2 feet fromt he bottom.

A leak in the bottom of the first chamber renders it defective and the result could be little or no liquid going on to the second chamber.

The second chamber could be an oxidation chamber but would need an air pump for that purpose. Otherwise it is just a settling chamber so that for any sludge that escaped from the first chamber, most would settle here rather than proceed to the leach field. If there were no second chamber then sludge from the first chamber would degrade the leach field in short order.

Now that you just had the first chamber pumped, nothing will exit to the second chamber until the liquid level gets back to the 85% or so point (and also the inlet pipe is replaced or repaired to eliminate leaks).

 

Thanks - so would you fill the first chamber to 85% full today with the garden house. I worry that it might take it two years or so to reach 85% from just the two of us using the toilet.

 

Do not waste time or money or water filling the septic tank to 85% unless you have an urgent need to conduct tests of the normally and fully operating system.

No new malfunctions will occur letting the septic tank fill up in the normal fashion no matter how slowly.

No additional odors will be experienced in the house while the septic tank after pump out refills compared with the septic system in full swing at 85% full sending liquid the usual gallon at a time to the leach field as each gallon of new waste water comes from the house.

To test the leach field, continue digging until you find the distribution box and pour water in there using the garden hose.

Some systems use a seepage pit instead of a leach field. This is the last tank in a septic system and is porous and is built like a dry well. It may be second or third or fourth depending on the complexity of the system. (A seepage pit that is the first and only tank is called a cesspool and a system containing that is not called a septic system.)

 

I know that you had the 1st tank pumped (last week); and I know that the 3rd tank is "bone dry"; but what's the condition of the 2nd tank ?

And at this point, you don't know yet whether the 3rd tank was the terminal point (drywell) or if the effluent continued on from there to a leach field ?

I think you'll be surprised how quickly two adults will re-fill an 1100 liter tank . . . . that's only 290 US Gallons, so all three of your 1100 Liter Tanks combined are less than one 1000 Gallon Conventional Tank here in the States.

 

Well all the 4" PVC that we are going to replace has been replaced. There were places where it just wasn't worth the effort - like where the PVC ran in parallel to a 6" thick concrete pipe ('clear' water).

The first thing I did this morning was (using a sump pump) drain the second tank - since I'm sure that 'water' has been sitting there for years. Then, using the new 'trap' near the house and a garden hose I filled the first tank to the point that it flowed over to fill the second tank and finally made sure that the second tank would properly overflow into the 'seepage pit'. Then I used the sump pump to once again drain the second tank. They are now cleaning out the bottom of the seepage pit - something which I know has never been done in the 20 years this house has been here. We had to cut a hole in the concrete top to gain entry. There is no fan on top of the pit but there is a 3" PVC tube which runs about 30' to a wall and then up perhaps another 20 feet. A 'ventilation' tube.

The plumber announced this morning that today is the last day he and his crew have to work on this system and I will need to finish the job (fill the holes and replace the sod myself). We had the same thing happen once when we lived in Florida and a woman under-quoted a job to re-sod our lot. At the end of the day she said she would require an additional day to finish the job (at twice the cost). My wife and I put on our gloves and we all worked until early night to get the job done.