Septic tank

txdon · Dec 12, 2014

I had my septic system pumped out today after 5 years - no problems.

The system is 750 gallons, two round cement tanks connected by a 4" PVC then draining to a field line in a field of deep sugar sand.
He did notice more sludge in the second (250 gallon) tank.

The pump guy also noticed that I did not have a sanitary T on the 4" pipe coming into 500 gallon septic tank. It was just a straight 4" PVC pipe.

The out going pipe did have an elbow and an extension piece that went down 16" into this 500 gallon tank.

The out going pipe out of the 500 gallon tank goes into a 250 gallon tank and again it was just a straight 4".

The out going pipe out of the 250 gallon tank did have an elbow that had a 4" PVC going down 9" into the tank.

Do I need to add sanitary Ts to the two 4" PVC pipes coming into each tank?

If so, how far should I extend the pipe going down on the Ts?

Or should I leave everything alone because it's working?

(Now is the time to make any adjustment while the level is low.)

JBourquin · Dec 12, 2014

The new tank I just bought had a "T" on the inlet side. I'm still not 100% sold on it. If anything going into the tank floats, wouldn't that cause a blockage there? I guess it depends on how high your inlet pipe is above the top of the scum line. If there's a possibility of scum backing up into the pipe you should have a "T" on there.

MAN IN BLACK · Dec 12, 2014

The exact purpose of the T's, is to prevent blockage from sewage or solids inside the tank blocking the inlet.
I would put some on...better be safe than sorry...picture yourself trying to free a blockage in the inlet...nasty, dirty , smelly and very unpleasant job.

HeLa · Dec 12, 2014

while you have dry access, i would put a sani-tee on the inlet of both tanks. they help attenuate the flow and increase the settling of solids. additionally, if you don't have an effluent filter on the outlet side of the second tank i would add that as well. this helps keep solids from entering the field. note that you'll probably want to have riser access to this filter for servicing it without digging.

oosik · Dec 12, 2014

Properly designed - a septic tank will have an inlet baffle - a baffle between the first & second compartment and a baffle on the outlet from the tank. These baffles can be cast-in-place or 4" plastic "T's". The exact design of the baffles is dictated by local sanitary codes/laws.

Western · Dec 12, 2014

oosik said:
Properly designed - a septic tank will have an inlet baffle - a baffle between the first & second compartment and a baffle on the outlet from the tank. These baffles can be cast-in-place or 4" plastic "T's". The exact design of the baffles is dictated by local sanitary codes/laws.

Mine has those backflo thingys, but I wish I had had them install an access at the exit point of the last tank for adding root killer that foams..

txdon · Dec 12, 2014

This septic system is grandfathered in and it is what is - acutally working pretty good - the lines have never clogged up. It's on top of a sand hill.

The inlet to the 500 gallon tank is about a 1/2" above the scum line. There are no baffles only the two connecting tanks (500 and 250 gallon).

So, if anything going in floats, will it be will be stuck in the T and cause a backup until it sinks or comes out the top of the T? Could this back things up?

I'm going back and forth on this - to T or not to T the inlets, that is the question.

The decision has to be made soon the level is rising.

PILOON · Dec 12, 2014

Recently a client's system was backing up and I was called to consult.
System was pumped last year as it is every 2 yrs in compliance with bylaws.
This is a chalet that is not heavily used.
I discovered that the solids had accumulated and hardened in that they exited the input and literally stopped by the baffle.
A simple poking with a stick collapsed the foot long 'plug' and everything returned to normal.
I instructed them to flush a lot of water in the future.

At first it simply looked like someone had inserted too much pipe and it was only when I poked with a stick to show them what I meant that the 'plug' dropped away. (dirty pipe and the 'plug' all looked the same color and was perfectly round as well)

All this to say baffles may not always be a good thing and I think unnecessary with dual compartment tanks or dual tanks.
I'd personally leave well enough alone.

Raspy · Dec 12, 2014

One of my septic tanks has a tee on the inlet pipe of the first section. It doesn't make a lot of sense to me and my neighbor recently had a clog there on his system after coming home from vacation. The septic guy told me the tee was to allow gasses to flow back up the pipe and get to the vent. Maybe, but an open pipe would do the same thing. I'm careful to send plenty of water down the pipe before leaving for any period.

The downturned pipe that leads to the second section prevents solids that either float or sink from getting through to the second section.