haeavy rain and septic question...

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New Member
Feb 2, 2010
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We live in western Washington in a house built in 1960 and has a sunken backyard and septic. Every year when the rain comes, my backyard gets not only our water run-off but our neighbors water too (long story). We have a sump pump way in the back, lowest part of our yard, that spits out the ground water 100' away, but the lawn over the drain field still stays soaked until about May when the weather changes. We have lived here for five years with no problems, but we had a slight problem two weeks ago when our groundwater pump got clogged and the backyard flooded, more or less, before we caught it. This has happened a few times before with power outages and whatnot and we trash-pump it out and everything is fine. This time, we noticed our basement toilet wasn't flushing right; high water level, making a gurgle sound as it drained. We also noticed a small puddle above where our septic tank is located that fluctuated with the toilet usage. We decided to have our tank pumped immediately.When the guy came out, he dug up the lawn about 14" down and said that the tank lid - an old concrete tank - was leaking groundwater into the system. He pumped the tank and said the outlet baffle was missing and that the sludge layer was gone as a result. He looked at the d-box and showed us how when he pumped out the d-box, there was sludge coming back from the leech pipes into the d-box. After some further inspection he suggested the following:
Risers on the inspection hole and main hole for the tank to keep groundwater from entering the system; replace the baffle; run a snake camera through the leech lines to check the health of the drainfield and lastly; vacuum out the leech lines to clear out the sludge.

The next day they sent out a "specialist" to re-inspect and do the work. When he got there he noticed the water table was above the lid of the tank, which is why he again suggested the risers. So he re-pumped the tank (it had poured rain all night); put on the baffle and the risers and he assured me this would seal the tank 100% from groundwater. He opened the d-box and fed the camera through the leech lines and said there was too much muck to see anything. So they vacuumed out the leech lines, which took about an hour, and re-checked with the camera. This "specialist" who was there doing the work told me he was an certified "O&M" inspector, which he said meant he was specialized/qualified to determine the health of septic systems by certain counties in our are that are sensitive to water quality for various reasons. Basically, he was a "super-inspector" was what he was saying. Anyhow,after the vacuuming and inspection, he said there were no puddles in the lines and the d-box "leveled-out" - whatever that means - and that our drain field was fine. He theorized that the annual deluge of water on our lawn probably helps keep our system clean and oxygenated.

Since the work was done, 2-1/2 weeks ago, we have no puddles and no funny toilet issues. I do notice, however, that when I peak in the inspection hole of the new risers, the liquid level is pretty much at the top of the tank, maybe an inch or so of air in there. I don't know if this is normal, but it seems like it might be from what I read here. Obviously there is no scum layer yet, because we had it pumped out two weeks ago and the scum layer was missing because of the baffle, So I assume the new scum layer will take some time to develop. I am paranoid about a drain field failure but I don't think it's the case because during the summer, the lawn dries up and the sump pump hole dries up too, so I assume the high water table goes down as well (I have never checked). I guess I am just looking for reassurance or advice. Is there anything I should keep an eye on or be worried about? We have never had a backup or slow drains or anything. I don't know much about septic, but I am educated in treating it right and have been since we bought the house. we are religious about the things we allow to go down the drain and we only do 1-2 loads of laundry a day. I also just switched out me toilet to a low-flow (thanks to this forum for help there too).

We were just annexed into a city that will provide sewers down the road (3-5 years), so I really want to keep this septic system running until then if possible.

Sorry for the long post...


Supporting Member
Jan 17, 2010
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Orlando, FL
Firstly, while I have messed with septic systems a LITTLE bit, I am far from qualified to comment with authority. So if someone disagrees with me who actually knows what they are talking about, ignore me.

I am assuming that your leach field is gravity fed from your septic tank. If it isn't, meaning that your leach field is higher than your septic tank, then you have to have a pump to lift the effluent up to the leach field. Assuming a gravity fed system, I would think that if groundwater were high enough to flood the system through the servicing and inspection ports of the septic tank, that the groundwater would also be high enough to effectively drown out the absorption abilities of the leach field. So it is my opinion that adding risers to the septic tank, while not a bad thing, probably won't magically fix your problem. Pumping out the leach field will probably help remove some solids that otherwise would clog if up and compromise it's effectiveness. Adding the outlet baffle is a really good thing, as it will help keep solids out of the leach field.

But your big problem is the really large runoff that you experience. Supersaturated soil does not want to absorb more liquid, so when your back yard floods, you run the risk of having septic system backups.

I also should add that as long as your sump system that clears the excess runoff is operating properly, I suspect that you should not have major problems for the forseeable future. Especially since the contractor that you had out did not try to sell you a new system, which would be a payday for them.
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Retired Pump guy.
Jan 6, 2010
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Murphy, NC.
I'm in the same boat as Phishfood, I'm not an expert. Raising the tank inlet can't really help in any way that I'm aware. Other than possibly keeping dirt out that may have been getting washed in through a non sealed tank lid. The fact that your yard is flooded and the drain fields are also full of water means that the tank and fields would be full all the time your yard is flooded.

Gravity is your friend in situations like these. Since the sinks, tubs and toilets are slightly higher than the drain field and top of your yard, the water is going to try to get out somehow. Maybe not as fast as desired, but nevertheless it will get out.

Septic tanks are always full of water right to the outlet elevation of the drain fields outlet. This is normal.