Undated (AP) _ When it rains, it pours for businesses that sell sandbags, pumps and other flood-related merchandise to water-laden residents along the Mississippi River.

''If we had beautiful, 70-degree weather ... our business would be terrible,'' said Bob Votroubek, owner of Rock Island's Handy True Value hardware store in Illinois.

His water-pump sales have quadrupled so far this year as residents try to save inundated basements.

Other hot-selling items include poison for rats carried near homes by flood waters and bug spray for insects that thrive in rain and humidity, Votroubek said.

The worst flooding on the Upper Mississippi since 1965 has swamped low- lying homes and businesses, blocked vital roads and bridges and halted shipping and recreational boating on most of the river north of St. Louis.

For a sandbag seller in Moline, Ill., business had been booming - but so were the flood waters.

''We're 100 percent encased in water,'' said Mike Zeitler, a supervisor at Moline Consumers Co.

Zeitler had been selling thousands of sandbags until the water isolated his store and business was brought to a halt late last week.

Normally the store has about 10,000 to 20,000 sandbags on hand, at 50 cents each. Zeitler estimated he sold 75,000 within the past week or so, marked down to 38 cents each for large orders.

''We weren't in it to make a killing. It was more of a service,'' he said.

Lightning from the flood-producing thunderstorms has shorted many underground pumps, meaning a boom in business for John Liberg's Apple River Well & Pump Co. of Hanover, Ill., near flood-stricken Galena.

''June business is doubled what it normally is due to lightning,'' Liberg said.

''We've started as early as 4 o'clock and finished as late as 10 at night,'' he said. ''You do profit off their misery but still provide an excellent service.''