Slow drains can be caused by several different things. If it's bathroom tub / sink - usually the first suspect is hair / soap / toothpaste / shaving cream that can glom together in the trap, or other areas near the trap.

If it's several places, it can be a main drain issue. They will run the main drain to clear that out.

If they have reason to suspect tree roots or damaged main drain, they will run a camera down the sewer. Usually if you are talking roots, it's in an older house that has clay tile sewer lines.

In my area, it's common for drain cleaning folks to sell the owner on installing an outside cleanout. This allows them to run the sewer from outside instead of inside the house. Sometimes it's questionable if that's really needed.

If they run the main sewer and tell you there is damage, you should get the photos of the damage and get at least a second quote.

Every homeowner needs to own a drain auger. Self sufficiency is non negotiable. Snake the drains, and snake the vents both. That is just normal seasonal maintenance. Same as caulking the air gaps around trim, etc.

Only after you've tackled standard cleaning, and there is still an issue, do you bring in the $500 plumbing visit to look at that.

Thanks Minardi….this is helpful, when you say seasonal do you mean once a year or every season (4 times a year) - we live in Miami Florida if climate makes a difference.

Start with a bottle or two of Drano.

Bouncing off Minardi's self-sufficiency comment: Always try the cheapest option first. You can buy a drain auger for less than the cost of a plumber's visit -- so that's a smart choice, especially as you will then have the auger for future issues.

Less happy: A few months ago we had to replace ALL the plumbing pipes in our 1970 house. Over 10K -- ouch, but we've had plumbing problems galore since we've been in this house. I'm hoping we're DONE now.

There will be a clean-out plug someplace in the floor right before the main line that leaves the house and is required by code. But as Jake stated your problem is more than likely before the main line and at the traps or at a tee or elbow in the branch going to the main line. A easy to use $25 drain auger from a hardware store is usually all that is needed to unplug these minor blockages.

If flushing your toilet was slow to drain or overflowed and the trap built into the toilet was eliminated as the problem then this would be a sign the main line had a blockage or damage. A plumber telling you the main line needs cleaned with a cutting auger when there isn't problems flushing the toilets would be a lie. On the other hand telling you running a cutting auger through the main sewer line to remove debris and grease buildup as be preventive maintenance would not be a lie and would indicate his honesty (and desire to make more money). Few people ever do preventive cleaning on sewage lines so consider this and make your choice.

If the plumber states your main line needs replaced do not hesitate getting a second opinion!! There is a slim chance a main needs replace in a 1970's house but fraud like this still happens and will cost $25,000 or more to replace the main to the street and big profits for the plumber.

In no way is rodding your (branch) plumbing a yearly/seasonal maintenance item. And you would need to rod your vent stacks every . . . never. Having an auger on hand is only fitting if you do lots of other kinds of DIY, as those little 1/4" hand or drill augers are just for sinks and can't handle true blockages down the line. You'd have to take apart the Ptrap and that in itself is beyond most homeowner's desire.

But, since you said multiple bathrooms, when Draino doesn't work, you can remove the vanity pop-up stopper and pull out hair with needlenose/tweezers. Gurgling sounds in adjacent fixtures might mean they share a wet vent.

It could be a larger issue with the type of plumbing too, as many DIYers use galvanized piping (which corrodes and the inside size gets smaller) or flexible plastic pipes under the sink. Or depending on where the bathrooms are, it could be a main sanitary line issue, but you would have more issues than just say a slow draining vanity sink.

My friend taught me this one: for a slow sink drain, try plunging. Plug the sink overflow holes first, then just use an ordinary plunger to see if that clears the drain.

No one is suggesting a $700 power drain augur for a homeowner to clean out their drains. But only bald people can get away with not doing an annual drain cleanout with a $30 one as a preventative measure. Long hair households may need to do it more than annually.

Whatever you do, find a local plumber by asking neighbors and friends or asking on a local facebook or Next Door page. Don't call a big company that advertises a lot. Where we live, there are several of the big companies, and I have never heard a good story about the companies, overpriced and upselling. A local person will be more likely to want to have customers come back in the future and depend on your recommendation to your friends.

There are different kinds of plumbers who usually choose to focus on a specific task. Some plumbers only install complete plumbing systems in new construction. Some plumbers only do rodding of pipes. It is perfectly fine to use a national "rodding" brand, who are franchised local people who may very well live down the street from you. They are not evil, they just wanted the marketing and administration support the national brand provides.

Again, there is a big difference between having blockages in your main sanitary line (which hair can exacerbate that started from a different cause), and hair/buildup wrapped around the stopper of a vanity sink or tub drain which causes a slow draining.