Older houses present maintenance and repair challenges that can seem overwhelming to the first-time homebuyers.

I’ve always believed that among the gifts a real estate agent gives to the buyer at closing should be a book on how to deal with problems that might have been hidden from even the most thorough home inspector or come up without warning.

Most home books don’t focus on the little things, or they tend to make things so complicated that the only words that should appear on each page are “call the plumber” or “hire an electrician.”

Those are the two trades I hire most often, but it would be nice to know something about the problems these professionals handle for you.

In addition, if the toilet is clogged, you may not need to call a plumber, but can clear the obstruction simply by having a go with a plunger.

So periodically in this space, I’m going to present some basics on home repair and maintenance that I’ve come across over the years, and that have come in handy in my houses.

Today we’ll tackle basic plumbing.

Water is supplied to your house from mains in the street or from a well. Once inside, the water travels by ½-inch or ¾ inch – depending on code – pipes to fixtures such as toilets, shower, the dishwasher and the washing machine. The used water is carried to the sewer or septic tank by a drain. Vents – usually on the roof but at least higher than the drain – provide air to, in effect, push the wastewater down and out.

So when you have plumbing problems, it can involve one or more of these things.

For example, wastewater in the kitchen sink goes down the drain. If you look under the sink, you’ll notice that drainpipe looks like an “S.” It is s-shaped (or sometimes “P” shaped) to prevent sewer gas from coming back into the house.

Because of its shape, this pipe or “trap” tends to become blocked -- especially if you throw stuff down the sink that really belongs in the garbage pail. If you’re going to stuff like that, you should have a licensed plumber (or you can do it if you are handy) install a disposal that will grind up food matter (no bones, please) so that it will pass easily through the pipe and down to the soil pipe.

Once the wastewater gets past the trap, it heads to vertical cast-iron or PVC plastic pipe (again, that is a building code issue for your area) called a soil stack. All the drain lines in the house flow by gravity into that stack.

That stack, which connects to the main sewer line, runs from the basement to the roof. At the top of the stack is a vent that lets the air in so that the wastewater can travel freely. The vent also balances the air pressure in all the drain lines throughout the house to keep things flowing.

Sometimes, that vent can become blocked with leaves or squirrel and birds’ nests, so it needs to be checked periodically. That’s the system. Now, we’ll look at one way to keep the various parts of the system working properly, and talk about others in subsequent columns.

Let’s try to unclog a toilet.

How do we know a toilet is clogged? Water flowing unimpeded all over the bathroom floor is pretty obvious, but you have to develop that sixth sense that such a problem is getting ready to occur.

Take off the cover on the toilet tank. When you flush a toilet that drains freely through the S-shaped pipe, the water in the tank and bowl disappears quickly and almost immediately, both begin to fill up again.

The tank begins filling and, at the same time, supplies water to the bowl. Once the water in the tank reaches the proper level, both tank and bowl stop filling.

If the water drains slowly and doesn’t vigorously clean the bowl, you know there’s a problem. Don’t flush, because the next time, the new water coming in from the tank will combine with the water that failed to drain, and you have a flood.

There should be a valve on the water supply line to the toilet. Shut it off.

Then you can begin plunging vigorously until the water and waste matter drain from the bowl. If you are confident the clog has been removed, turn the water back on and then flush, but be prepared to shut off the valve again and keep the mop handy.

How do you keep the toilet drain clear? Don’t flush diapers, sanitary napkins or paper towels down the toilet, because unlike toilet paper, these don’t degrade quickly and they can accumulate in the S-trap as well as in the soil stack.

If the problem persists, call a plumber.

Published: May 1, 2003

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Al Heavens writes about real estate and home repair and improvement. He is the author of What No One Ever Tells You About Renovating Your Home: Real-Life Advice For Hassle-free, Cost-Effective Remodeling.