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phillyd2 10-16-2007 01:34 PM

Septic holding Tank Settled
New home where the soil is mostly clay. During a repair to the PVC tube from house to holding tank they found that the tank must have settled since the inlet water only dropped about 1.5". They said it should fall about 3-4". The recommended quick fix was to drill on new out hole (to pump tank) about 2-3" lower. Tank has been in for over one year and they think it may have settled all that it will but nobody knows for sure.

Thoughts on the fix?

The other option would be a brand new tank!


Mike Swearingen 10-16-2007 07:54 PM

WHAT??? This doesn't make sense to me.
The main drain pipe should slope about 1/4" per linear foot to the septic tank.
A septic tank is pumped out from a clean-out on top (usually has a small rectangular beveled concrete cap), not from a side hole.
If a tank has "dropped" or "settled", the pipe would be lower, not higher. I don't understand what they're telling you.
Get another opinion, preferably from a technician at your Health Department which is responsible for inspecting and permitting septic systems, and not selling you unnecessary work.
This sounds more like a rip-off to me.
Good Luck!

phillyd2 10-16-2007 08:05 PM

OK, sorry for not explaining it better.

The Health Dept passed all with flying colors but we had a indy inspect check it out, just to be sure. The main drain pipe was holding water when they looked through with a camera so clearly something was amiss. They dug up and found that the main drain pipe from the house was kinked so it was replaced and set with the 1.25" drop.

Now, after the fix he said that the water from the house through the new main drain pipe going into the tank only fell about 1.5" into the tank (before hitting exsisting water in the tank). This he called the inlet. From what I understand the outlet on the other side of the tank is suppose to be lower than the inlet hole by about 3-4" which would normally mean that the water from the main drain pipe should fall about 3-4" into the tank. Instead it only falls about 1.25" which means that the one side of the tank has settled.

Hope I now better explained it.

Mike Swearingen 10-16-2007 08:46 PM

O.K. Now it makes more sense to me.
There should be a vertical T on the discharge pipe to prevent sludge, grease, etc. from getting into the distribution box and clogging the drainfield lines, and yes the discharge should be a bit lower than the inlet line.
According to NC state sources, septic tanks need to be pumped out at least every five years. I have our 1977 tank pumped out in every year that ends in a 0 or a 5.
Good Luck!

NateHanson 10-17-2007 06:39 AM

It sounds like they've scoped this tank a couple times, even dug up the input line for repair, but have they never opened up the inspection covers on the tank to see what's going on inside? On my tank there are 3 inspection covers. One big one over the center, and smaller ones on each end, covering the inlet and outlet. I'd expect a visual inspection sometime in all of this. How do they know that the tank has settled on one end, and not that your leach field is clogging up, or that there's solids blocking the outlet partially, so that the water level in the tank is a couple inches higher than usual. This sounds like a strange inspection method to me. Tell them to get out a shovel and get their hands "dirty". :)

jogr 10-17-2007 10:26 AM

If they drop the outlet then you won't have the right slope to your leach field.

If the inlet side really settled 2-3" then wouldn't the slope of the main line from your house to the septic tank have been wrong when originally installed? If it only drops 1.25" from the house to the tank now and the tank was 2-3" higher then the line would have sloped up from the house to the tank.

Why in the world would you need a new tank if there is nothing wrong with it. If it settled then it might need to be reset but certainly not replaced.

It sounds like the whole works was installed incorrectly and you have a conflict between the height of the leach field and the height of your main line. This could be expensive to fix. Is you builder paying for the fix? Make sure you have a good independent inspector so you don't get a bandaid fix that you'll have to live with.

phillyd2 10-17-2007 10:35 AM

Not sure if this would clearify the situation by our system is as such:


The PVC Pipe from the House to the Holding Tank is what was replaced due to kinking. Since the soil is very wet & heavy clay they think it must have bent under the weight. The new PVC pipe is now covered with concert so it should hold.

The new issue is that the waste from the main PVC pipe goes into the Holding Tank. This is where they are saying the waste water only drops 1.5" before hitting the water that is in the tank, which they say should drop 3-4" before hitting the exsisting water in the tank. They want to lower the hole / pipe that goes from the Holding Tank to the Pump Tank so that the waste water INTO the holding tank drops the needed distance.

Again, the system has been in for about one year but its new constuction and we have not even moved in yet. Anything in the tank is just from workers using the system recently.

jogr 10-17-2007 11:33 AM

If you are paying for these repairs I hope that you hired someone else besides the original installers.

I don't care what kind of soil you have, the line shouldn't have kinked and the tank shouldn't have settled. Covering the line with concrete will only add weight on top and make future repairs a pain. The line kinked because it wasn't supported properly on the bottom. If the tank settled it was not installed on undisturbed soil or properly compacted fill.

Blaming clay is misdirection. It has absolutely nothing to do with the failures.

Will your local authorities allow modifying the tank and decreasing it's working volume? Will you have enough slope between the septic tank and the pump tank?

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