Which of the septic tank rules are real and which are folklore? First house with a tank and I have been given contradictory lists.

Fifteen years on a tank, and the bacteria packet question deserves a direct answer rather than a diplomatic one: a functioning tank is not short of bacteria. It receives a fresh supply several times a day from the thing it is designed to receive.

The situation where additives get discussed seriously is after something has genuinely wiped the tank out, which is rare and is not a monthly maintenance scenario.

The person to ask is whoever pumps your tank, because they see what is actually in there, and their list is much shorter than the internet's.

Sorting yours:

Wipes, completely real, and the worst thing on your list. "Flushable" means it clears the toilet, which is a much lower bar than breaking down. They do not disintegrate, they knit together into mats, and they are the number one cause of blocked pumps and filters. Nothing but toilet paper. This one is not folklore in any degree.

Garbage disposal: real, and underrated. It adds a large volume of solids that break down slowly, so the sludge layer builds much faster. Systems with one need pumping considerably more often, and if you do not increase the frequency to match, solids carry over into the drainfield, which is the expensive failure.

Bleach and cleaners, mostly overstated. Normal household use, in normal amounts, diluted by everything else going down the drain, is not going to sterilise a tank. Where it becomes real is volume: pouring a lot of anything strong down at once, or a hobby that puts solvents or paint into the drain.

Softener discharge, genuinely debated, and there is more to it than a yes or no; someone will cover it below.

Additive packets: no. This is the one being sold. A working tank is populated continuously by what enters it. There is no shortage to correct.

I removed my disposal after a conversation with a septic contractor and I would do it again, but the honest version is that it is a maintenance-frequency question rather than a destruction question.

A disposal does not break your system. It changes the arithmetic: more solids in, sludge layer rises faster, and the interval between pump-outs shortens - the figures people quote vary, but the direction is not disputed. If you keep the disposal and pump on a schedule that accounts for it, you are fine. The damage happens when people keep the disposal and the pumping schedule they inherited, which is the common case.

What actually matters more than any single item on your list is pumping on time, and the reason is worth understanding. Solids that stay in the tank are harmless. Solids that carry over into the drainfield clog the soil, and a clogged drainfield is the failure that costs many thousands and cannot be undone by pumping. Everything on the folklore list is really a proxy for "do not overload the tank between pump-outs".

So: composting or binning food waste, a sensible pumping interval for your tank size and household, and knowing where your tank and drainfield actually are. That is most of it.

The one that is missing from every list: know where your tank and drain field actually are, and do not park or build on the field. That will cost you more than every item on this list combined and nobody mentions it because it is not a product.

Ask the pumper is genuinely the best advice in this thread.

On the softener, since it is the one on your list with a genuinely unresolved answer.

There are two separate concerns and people conflate them:

Salt harming the bacteria. The research on this has gone back and forth and the current weight of opinion is that at normal regeneration levels it is not the problem it was once thought to be. Not the reason to worry.

Hydraulic load. This is the real one. A regeneration cycle dumps a large volume of water into the tank in a short period. That surge can stir up the settled layers and push solids toward the outlet - the same mechanism as the drainfield problem above, arriving by a different route. It also adds meaningfully to the total volume the drainfield has to absorb.

What to do about it depends on rules where you are, in some places discharging a softener to a septic system is not permitted at all, so that is worth checking before anything else. If it is allowed, a demand-initiated softener that regenerates based on use rather than on a timer cuts the number of cycles a lot, and that is the cheap improvement.

General point for a first-time owner: the local rules are not uniform, and your area's requirements for tank size, inspection and pumping intervals are the actual answer to a lot of these questions. Worth finding out what they are before adopting anybody's list, including this one.