Tomatoes can be grown in pots-usually at least 18" wide. Water them in the morning if the leaves look limp or if the soil six inches down is dry. This is when a hand held meter comes in handy. Check the soil again at mid day. At mid day you can't be relying on the leaves and whether they look limp-they should becuase it is hot and sunny. It's tough to overwater a tomato plant that is growing in a pot.
Remember that since you are watering so much you are washing away fertilizer faster than normal and therefore should be feeding more frequently then recommend on the plant food box. If it ways to feed every six weeks, use a three week schedule instead.
