diff --git a/web/ons-demo/js/iperf.js b/web/ons-demo/js/iperf.js
index 8b1db26..b74175c 100644
--- a/web/ons-demo/js/iperf.js
+++ b/web/ons-demo/js/iperf.js
@@ -77,6 +77,7 @@
 	if (flow.flowId) {
 		iperfLog('starting iperf', flow);
 		startIPerf(flow, duration, updateRate/interval);
+
 		flow.iperfDisplayInterval = setInterval(function () {
 			if (flow.iperfData) {
 				var iperfPath = d3.select(document.getElementById(makeSelectedFlowKey(flow))).select('path');
@@ -182,7 +183,8 @@
 //				iperfLog(data, flow);
 			});
 		}
-		fetchData();
 
+		// wait a buffer to make sure the old iperf session gets cleared out
+		setTimeout(fetchData, updateRate);
 	}
 }
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