//<![CDATA[
        function getwater() {
            var sId = document.getElementById("roof").value;
			var sId2 = document.getElementById("rain").value;
            var oOptions = {
                method: "get",
                parameters: "roof=" + sId + "&rain=" + sId2, 
				onSuccess: function (oXHR, oJson) {
                    displayCustomerInfo(oXHR.responseText);
                },
                onFailure: function (oXHR, oJson) {
                    displayCustomerInfo("An error occurred: " + 
                                                       oXHR.statusText);
                }
            };
            var oRequest = new Ajax.Request("watercalc.php", oOptions);
        }
        
        function displayCustomerInfo(sText) {
            var divCustomerInfo = document.getElementById("divCustomerInfo");
            divCustomerInfo.innerHTML = sText;
        }
        //]]>