Septic / drain leachfield system question

Hi Everyone.
I'm in need of an unbiased advice about my septic system.

When heavy rain or fast thaw hit, water backs up from our septic tank into our pipes, so that it flows back, even when we don't use any water inside the house. The house is located in front of a mountain with tank and field below a steep hill (see photos). The house was built in 1970s, mostly used as a vacation home, now we live here full time. It is a gravity fed system (that's what inspector told me), tank is baffle concrete tank, 1500 gallons. Previous owner passed away a few years ago, so I don't have any paperwork or plans of the set up. There are no visible problems, unless it rains really heavy, so basically 99% of the time, there are no wet spots or such on the field. Where would I start fixing this?

As I understand, there are 2 major things that can be going wrong:
1. water flows can be coming down the mountain, saturating field and overflowing tank or
2. tank has a crack, and when there's a lot of water it comes in and overflows it back into the house. Just my guesses. As far as solutions, I understand that if tank has a crack, the whole tank is usually replaced. If it is the field that gets over saturated when it rains heavily, can that be fixed by not touching the actual field, but rather digging something like a french drain at the edge of mountain and field? If this is the case, how should this drain be constructed, the depth etc?

I called a professional and they'll come up in a few days, but I'd like to have
some ideas before hand.
Thanks in advance for your input, it's VERY MUCH appreciated.

Do u live in that little tree house. Just kidding. You might need a check valve installed. I do know if the tank is comprimised you will have to replace

Thank you for the advice. I thought about putting a backwater valve where the tank meets the drainfield. Got to do more research on that. Overall it will not solve the problem, just as an emergency measure ok.
P.S. If the problem gets worse, I might end up of living in that "little tree house"

Anybody else, please?

A french drain is what you need. You have to get the groundwater away from the system. There are regulations that say how far from the system it must be and also how deep. Talk to your building dept.

John,
Thank you for the input! I am having excavating contractor to look at things later today.
I do not believe field is failing, because even the field was built 40 years ago, it was only used about 2-3 month a year by a very cautious couple who did not pour oil or had a washing machine, so to do a French drain seems like a valid idea, it should by theory attract less water from the mountain.


My main concern is that water flows into the septic tank when it rains very heavily and I do not know how to determine weather it is from field or there is a possible crack in the tank. Tank was pumped out twice in 3 years I lived here. Visually it is sound, but there might be a very thin crack that is not apparent. I wish somebody could give me a hint list/steps of what I should look for to determine problem.
I took one step last year and had a professional install a septic tank riser, thinking that water could of entered from the surface, that did not help.

Any other advice / suggestions would be greatly appreciated.
Thank you.

Any french drain would be deeper then the bottom of the tank removing the ground water that can enter the tank. It sounds like what is happening is the ground water is flooding the fields to the point that it enters the tank from the outlet side of the tank.

Just had a visit from excavating contractor. He gave me a price to do a french drain, but other than that very little help. What got me concerned is that he did not know about pre-manufactured french drain pipe similar to the one made by infiltrator, being in business for over 25 years, my guess he should have known about it.

But putting that aside, I am still like Alice in wonderland... What if it is
the tank that has a crack or such? doing a French drain would be useless then if
considering field is functioning properly.

It seems to me that the only solution would be to wait for a very heavy rain and beg one of the pump contractors have my tank pumped at the time of rain and just see if water is coming from the field or somewhere else. Am I right on this??

Thank you.

Well, I decided to take step #1 and try to divert water away from septic tank by doing a French drain. I think I will go with the pre-fabricated Infiltrator or NDS drain pipe(the one with poly rock and mesh sock) the only question is weather I should use a plastic liner. It seems like a good idea, since it would prevent any water seeping down and would also help to channel the water better. Did anyone have had any experience with liner?
Hope to hear back. Thank you!

The french drain should help in the long run to help prevent field saturation, so even if the tank was compromised, it would still be a good idea to do for the leach field.

I am hoping that your tank is not compromised.

I don't know about any of the liners so I can't help you with that. Sorry.

I do wish you luck on this. Please let us know how things turn out.