WE HAVE an early warning device," said Edward Tuck who sells Little Giant pumps in his pet shop. "When we notice a lot of the animals lining up at the front door in pairs, we know it's time to either get out the pumps or make an ark fast."

On Monday, after the worst of it appeared to have passed and the floodtides showed signs of subsiding, Tuck considered his prospects and proclaimed: "It's been a good day."

Tuck, as in Tuck Distributing Co., runs mostly a pet shop on 7th Street NW. Tuck was not a bit fazed by the three inches of rain that soaked the Washington area along with more than two feet of melting snow. In fact, he was ready for it.

Tuck had an ad running in the paper last weekend for his pumps -- the ones normally used in those cute little waterfalls and fountains and fish pools. "Tired of floodings?" the ad read. "Rentals and sales $25 up. Hundreds of LITTLE GIANTS in stock."

"We've probably done three months' sales in three days," Tuck said. He and a lot of other people. Many area rental and retail stores were all out of pumps on Monday. Montgomery Ward in Gaithersburg sent a man up to Baltimore to get more.

"We've talked to some people with five or six feet in the basement," said Buddy Johns at U-Rent Co. in Northeast Washington.

If there's any justice, we'll have seen the worst of it. But the question uppermost in many minds here is, "Can Washington handle a flooded basement without getting all wet about it?"

There are several ways of dealing with an inundated sus-terre . One of these, acceptable in some societies, is to file for immediate divorce and flee to the Tahitian islands. French painter Gauguin chose this route and look where it got him.

Another thing you can do is haul the stuff to a "dry" state, label it "branch water" and sell it for all you can gert. This will also qualify you to become a stock-car racing driver.

But by all means do it the easy way. This is to call a press conference, declare an emergency in your house and let them bring in the fire department. This is not a joke. Repeat. This is not a joke.

If in fact the flooding in your basement has reached epic proportions, i.e. you wake up in bed with your nose pressed against the ceiling, you have the option of calling the fire department. Fire officials say that if you can convince an officer it is an emergency, you will receive preferential treatment. Meaning, they will come over and pump out your basement for you.

But Washingtonians are a tough breed. Most will want to do it themselves.

If this is indeed the case, take heed. "If you've only got enough water to cover the floor or carpet, it's not much of a problem," says Leonard King, spokesman for fire and rescue services of the Montgomery County Fire Department. "But if there's enough to affect the hot-water heater, furnace or electrical utlets, you should not enter the water itself. The water entering. electrical equipment can cause damage. It can conceivably cause a fire and electrical shock.

"If you have that amount of water, where it is affecting the electrical system, then it's definitely time to call for assistance."

Many tool and equipment rental outlets rent different kinds of pumps. Many department and housewares stores sell them. They rent generally from $15- $25 a day. If you buy, expect to pay anywhere from $50- $150.

The thing to look for on a pump is the amount of water it wil remove in an hour at a specified "head." The "head" is the vertical distance from the pump to the end of a hose. You will find that a small pump that attaches to a garden hose might pump 120 gallons an hour at a one-foot "head." With a four-foot "head," it pumps 40 gallons an hour. These pumps are meant for cleaning out a stairwell or window well. Not for removing five feet from the rec room.

Montgomery Ward, for instance, has six pump models, with one-sixth to one-half horsepower, that sell for $55- $115. The most powerful of these will eject 3,480 gallons an hour with a fivefoot "head".

With any machine, the object is to run the hose into a drain that is low, so the pump can pump at its maximum.

Pumps also come with automatic or manual shut-off. When the water reaches a certain level -- about a half-inch or so -- most pumps will begin sucking in a lot of air. If the pump is a manual one, you must be around to shut it off at this point, lest it burn up. The better pumps shut-off automatically. Some will turn on automatically as well if the water level begins to rise.

"The main thing to look out for with a pump is one yuou drop in the water," a submersible pump, said Kenneth Winkelvoss, fire education officer with the Fairfax County Fire Department. He added, "Watch out for the wires." If you need an extension cord for the pump, make sure it is high and dry.

A common fault in pumping water from the basement is sticking the hose out the window so the water drians into the geranium bed next to the house. Water has a funny way of finding its way back in again if it is ot disposed of far enough away -- New York, for instance. Try to have enough hose to reach the street, or a drain such as the toliet or the laundry sink at least.

If water is coming in around windows or doors, King suggests channeling it away by digging trenches in the ground.

When the pump has sounded its last squffrrrt, you will still be left with a half-inch on the floor. You can mop it up, sure. Many places that sell or rent pumps, however, also have wet/dry vacuums that work like a regular vacuum cleaner. U-Rent rents these out at$12 a day. Naturally, you get to keep whatever you find in the bag.