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Aquarium air valves work well . I have used many of them . Just remove the barb ends and carefully solder them into your line .https://www.ebay.com/itm/116200367739?_skw=aquarium+valves&itmmeta=01JT45EWRE9N58NSRRZA26KV39&hash=item1b0e14e67b:g:F80AAOSwL~BmWOfz&itmprp=enc%3AAQAKAAAA8FkggFvd1GGDu0w3yXCmi1d0Be9yx9jIE8Gex22ZtyuOP0MFW%2F2Y3YBYd1AGyOAgLpHmZ%2F1rEXTb4A87OD%2F5nlaB8amIp%2FXh5bKCrhXvlNITUEIs7XzJjlsIGqlU3EE%2FdjqvDOpY20TsfM4rBepq67ZAJs%2Bs8HTo9ZdL1Xe5uAo0d71Os1STyrrHpYQDq3b6cRIpt7hMrC0abOvnCCSSnR7%2FbxxXqJz4aIUdNdpDZ5Kjo2Y9LgjfJkdSj6VkoeBDLmb0PQoeC%2Fx0kBQ55erXQPaRrx09dR2t9Wfa8bMI7Kkd7Q%2By5rUyyd4u30n6fj2dNA%3D%3D%7Ctkp%3ABk9SR6TNu4XRZQ