SPA & HOT TUB FLUSH 500ml .Spa & Hot Tub Flush should be used before the water is de-commissioned / drained down (typically no longer than 12 weeks for domestic spas and hot tubs) although heavy use will require more frequent drain downs. This product is formulated to internally clean all the pipework and fittings and will also loosen biofilms which can provide an ideal environment for harmful viruses and bacteria to live.