// show/hide the cistern

function showCistern() {

if (document.getElementById){
	
	if (document.getElementById('hs6').style.visibility == "visible" && document.getElementById('hs10').style.visibility == "visible") {
	
		document.getElementById('cistern1').style.visibility = "hidden";
		document.getElementById('cistern2').style.visibility = "visible";
	}
	else {
		document.getElementById('cistern1').style.visibility = "visible";
		document.getElementById('cistern2').style.visibility = "hidden";
		if (document.getElementById('hs2').style.visibility == 'visible') {
			document.getElementById('hs2').style.visibility = 'hidden';
			document.getElementById('hs1').style.visibility = 'visible';
			document.getElementById('hhl6').style.visibility = 'hidden';

		}
	}
	
	}
	else {
		if (document.layers){
			if ((document.layers['hs6'].visibility == "visible" || document.layers['hs6'].visibility == "show") && (document.layers['hs10'].visibility == "visible" || document.layers['hs10'].visibility == "show")) {
				document.layers['cistern1'].visibility = "hidden";
				document.layers['cistern2'].visibility = "visible";
			}
			else {
				document.layers['cistern2'].visibility = "hidden";
				document.layers['cistern1'].visibility = "visible";
			}
		}
	else{
		if (document.all('hs6').style.visibility == "visible" && document.all('hs10').style.visibility == "visible" ) {
			document.all('cistern1').style.visibility = "hidden";
			document.all('cistern2').style.visibility = "visible";
		}
		else {
			document.all('cistern2').style.visibility = "hidden";
			document.all('cistern1').style.visibility = "visible";
		}
	}
	}




	
	
}