QUESTION: Why are water towers round and elevated so high off the ground, and how do they work?

ANSWER: Most modern water tanks are circular horizontally and rounded on the bottom half, but the tops may be round or flattened. Designers rounded the bottom halves for strength, to hold up to 3 million gallons in the largest ones and to withstand the pressure from so much water. A half-sphere is a more stable container on stilts than is a squared-off box. Welding the parts together provides more strength than riveting.

Taking the water supply from a treatment plant, a high-pressure pump sends the water up into the tank through a pipe. The tank generally holds enough water to meet an area's demands for a day. At night, the tank is refilled while demand is low.

Towers are high and placed on high land to supply pressure that sends water down the tower pipes and into the feeder pipes to homes and businesses. Delivering water with pressure instead of with pumps is more cost effective.

After figuring out how much water is needed at peak times and what pressure is needed to supply that amount, tower designers can determine the necessary height, volume and shape of a tank, as well as required pipe diameters. In larger tanks, the top is flattened to provide more consistent pressure. A tall, narrow tank would have too much pressure when full and not enough when low.

Modern tanks close in the pedestal, hiding the pipes and ladders. The downside is you can't climb them any more to besmirch your football opponents.

Q: A couple of weeks ago, Longview ISD paid for a survey about the bond election and said it would be in the newspaper. What happened to that?

A: LISD spokesman Brian Bowman said John Green and Associates recently completed a phone canvass, but the results have not been released. A privately funded bond committee, not the public school district, paid for the survey. The committee is not required to release the results.

Q: What is John McCain's address?

A: John McCain 2008, P.O. Box 16118, Arlington, VA 22215.

Q: Where does potting soil come from? Is there a big hole somewhere?

A: No, it doesn't come from potting soil mines, and it isn't really soil or dirt, either.

Container plants need a lighter mixture than garden soil provides. Roots must be able to penetrate easily, and the mixture must drain fast but still hold moisture. Cheap mixtures dry up quickly and are not easily saturated. Potting soil was originally developed for nurseries, which needed sterile mixtures (no bugs or disease) and something that would allow roots to grow quickly.

Today, you get what you pay for. Baggers do not have to list the ingredients, so beware those that do not. You may get a bag of dirt. The best mixtures contain peat moss, composted forest products, shredded or ground bark, perlite or vermiculite and perhaps sand or charcoal. Sometimes lime is added to balance the pH. Watch out for "compost," as an ingredient, because there are no standards. It may be yard waste, sewage sludge or anything slightly resembling compost.

Ingredients and amounts vary depending on what you are potting. Mixtures often target a specific plant; for example, African violet mix, pansy mix or cactus mix.

Q: Which home shopping cable program started first — HSN or QVC?

A: HSN has been hawking its products longer than QVC. In 1977, a Florida radio station owner accepted 112 can openers from an advertiser who could not pay his bill and sold them on the radio. The quick sellout led to a regular program selling products, and in 1982, the show went on local cable. In 1985, HSN, as Home Shopping Club, went nationwide 24 hours on cable and local TV, becoming a publicly traded company in 1986. HSN's method was a high-pressure sales spiel and sudden price slashes.

Meanwhile, Joseph M. Segel happened to catch HSC while flipping through the channels. Segel, an entrepreneur, figured he could do the same thing, only better. He created QVC in 1986, changing the format from HSN's hard sell to a low-pressure experience. Salespeople studied products and gave viewers information about a product's sales history and benefits, in contrast to HSN's frenzied pace.

Dip call: A reader wonders if anyone has the recipe for the dip/sauce served with steak finger baskets at the old Dairy Kreme on South High Street. Call or write Answer Line, and we'll print it.

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