Straight answers.

Start at the house. The main sewer line leaves the building on the side where the plumbing is stacked. Walk that line across the yard — the tank is somewhere along it. Metal detectors don't help; there isn't enough metal in a tank to find.

Ask them things only someone who's done the work can answer.

Ask what pump is on the truck. The brand — and if you want to go deeper, the model. Ask about the gauges, because any pump truck driver knows the gauges. Ask about the trucks themselves; there are styles and there are types, and a man who's driven them knows the difference.

Then ask the real one: you pull up to a job and the customer has no idea where the tank is. What do you do?

A man who's done this work has an answer before he's picked up a shovel. A man who hasn't will tell you he'll have a look around.

Not the sinks. Sinks sit too high in the plumbing to tell you anything about your septic system. The first sign shows up at the lowest point running out to the tank, which in most homes is the bathtub. If the tub is slow, take it seriously.

No. A 1,000-, 1,250-, and 1,500-gallon tank are often the same physical tank. What changes is the height of the inlet and outlet baffles, which sets the retention time for the fixture count of the house. Every tank also has mandatory free space above the normal operating level. And the leach field holds water too. That's why a pump can pull more gallons than the tank's rated size.

No. They can create a better environment for the bacteria that break down the sludge and scum layers. They will never empty your tank. Anyone claiming you'll never have to pump again is not telling you the truth.

No — even the ones labeled "septic safe." They don't break down in the time a septic system is built for. We have pumped tanks that were completely full of wipes.

Listen to whether they ask you questions. Where is your tank? When was it last serviced? Does it have a riser? Why are you calling — maintenance, or are you backing up? A company that asks nothing is a company that will show up and explore your yard on your dime. Prescription without diagnosis is malpractice.

Because a septic tank is a living system. Too many people in the house and you overload it. Too few and you don't generate enough waste to keep the bacteria alive — the good bacteria die off and bad bacteria take over. Pumping every year restarts a healthy system either way.

Grease. Paint and solvents. Drano and heavy chlorine products. Non-biodegradable items: wipes, tampons, intimacy products, and diapers — adult and child. Hazardous chemicals can take years of pumping to clear enough for bacteria to recover.

Because what's left behind is startup bacteria, and the system needs it.

If you pressure-washed a tank down and took everything out of it, you'd have what amounts to a brand-new tank — and a new tank has problems. When the concrete is still green, the pH is out of balance, and bacteria can't live in it until that settles.

It works the same way at scale. When a new wastewater treatment facility comes online, you don't wait for it to grow its own bacteria. You go to another treatment plant, pump the sludge out of their digesters, haul it over, and dump it into the new one. That bacteria is already generated and already working.

A septic tank is no different. Leaving some behind keeps the pH balanced and the bacteria alive.

Because it's supposed to be.

A septic tank has to sit at a certain level to work at all. People watch a truck pull a thousand gallons out, come back two weeks later, see the tank full again, and assume something's wrong. Nothing is wrong. That's the tank doing its job.

The water in the tank is what gives solids time to separate and bacteria somewhere to live. An empty tank isn't a healthy tank — it's a tank that isn't working yet.

It starts the separation.

When liquid enters the tank, the baffles create a circular motion. That motion is what causes solids to sink to the bottom and lighter material — grease, oils — to float to the top, where it forms the scum layer.

Most people picture a septic tank as a box that water passes through. It isn't. It's a settling chamber, and the baffles are what make the settling happen.

Because it's designed to.

All newer systems have filters, and the filter is built to slow and then stop the flow to the leach area if it isn't serviced. That's not a malfunction. That's what protects the leach field.

Wait too long and one of two things happens: solids overflow into the drain field, or the filter backs the system up into the house. A leach field is expensive. The backup is the cheaper warning.

Filter cleaning and pumping belong on a regular schedule. Newer homes especially — that filter is going to plug up.

Most residential tanks in Arizona fall between 1,000 and 2,000 gallons.

A three-bedroom home typically ranges from 1,000 to 1,250 gallons

A four-bedroom generally runs 1,250 to 1,500 gallons

A five-bedroom is usually 1,500 to 2,000 gallons, sometimes more

Bedrooms aren't really the number that matters, though. Tanks are sized on fixture count, because what you're buying is retention time. Ten faucets in a four-bedroom house move more water through the system than three faucets in a three-bedroom, and that water needs time to sit before it moves on.

Once liquid leaves the tank, it goes out to perforated pipes buried in gravel. From there it filters slowly down through the soil.

That's the whole system: the tank separates, the drain field disposes. Which is why anything that ruins the separation — grease, non-biodegradables, a plugged filter — eventually ruins the drain field too. The tank is what stands between your solids and the most expensive part of your system.

Eight things:

The pull from the house to the tank — whether waste is moving out of the home the way it should

The inlet baffle

The outlet baffle

The scum layer — what floats

The sludge layer — what sinks

Roots — intrusion into the tank or lines

Backflow at the tailpipe — waste coming back from the leach field

The water level — high or low, and both mean something

Each one gets a grade. Together they tell you whether the system is healthy, worth watching, or already failing.

More than most people expect.

Anytime a building's plumbing ends up too deep to connect to the city sewer line by gravity, it needs a lift station to pump the waste up. Build a Costco and by the time the plumbing is in, it's usually too deep to tie into the city line — so Costco runs its own private lift station.

The same is true of manufacturing facilities, government buildings, and shopping centers. Entire subdivisions run on them. So do individual homes that sit below the city line — Arcadia is full of them, because so many of those houses are built off the side of the mountain.

If you own or manage a property with one, it belongs on a regular pumping and cleaning schedule like anything else.