{"product_id":"castair-5-8x1-2-in-tank-check-valve-compression-tube-fitting-inlet-npt-outlet","title":"Castair 5\/8\"X1\/2\" In Tank Check Valve Compression Tube Fitting Inlet\/NPT Outlet","description":"\u003cp\u003eThe Castair CTD5812 is a 5\/8\" compression tube fitting inlet x 1\/2\" NPT male outlet in-tank check valve. It is the part that keeps compressed air in your tank when the pump unloads and prevents backflow when the system is at rest. If your compressor is bleeding down through the head or you need to replace a worn check valve on a Cast Iron pump, this is the OEM-sourced replacement rated for the pressures real shop equipment runs at.\u003c\/p\u003e\n\n\u003ch2\u003eWhat This Part Does\u003c\/h2\u003e\n\u003cp\u003eThe in-tank check valve is installed in the tank port where the pump discharge tube connects. It allows air to flow from the pump into the tank during compression, then seals shut when the pump stops or unloads — preventing reverse airflow back through the pump valves. A failed check valve shows up as the pump struggling to restart under load, excessive bleed-back from the unloader line, or the compressor failing to build pressure efficiently.\u003c\/p\u003e\n\n\u003ch3\u003eRated Specifications\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eRated Pressure:\u003c\/strong\u003e 500 PSIG maximum\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eRated Temperature:\u003c\/strong\u003e 400 degrees F maximum\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eInlet Connection:\u003c\/strong\u003e 5\/8\" compression tube fitting\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOutlet Connection:\u003c\/strong\u003e 1\/2\" NPT male (tank side)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSide Port:\u003c\/strong\u003e 1\/8\" for unloader tube connection\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eStyle:\u003c\/strong\u003e In-tank, compression fitting inlet\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePart Number:\u003c\/strong\u003e CTD5812\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eWhen You Need This Part\u003c\/h2\u003e\n\u003cp\u003eThe CTD5812 fits compressors where the pump discharge tube is 5\/8\" OD copper or steel tubing and the tank boss is tapped 1\/2\" NPT. This is a common configuration on medium-duty single-stage and two-stage shop compressors. Before ordering, verify your existing check valve's inlet tube OD and the tank port thread size — Castair makes this valve in a full range of inlet\/outlet combinations so the right match matters.\u003c\/p\u003e\n\n\u003ch3\u003eSigns the Check Valve Needs Replacement\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eBleed-back through unloader:\u003c\/strong\u003e Air exhausts from the unloader port during or after shutdown for an extended time, indicating the seat is not sealing\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePump loads immediately on restart:\u003c\/strong\u003e Tank pressure pushes back through a failed valve; the motor restarts against full pressure and trips thermal overload or blows fuses\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSlow pressure buildup:\u003c\/strong\u003e A leaking check valve allows partial backflow, reducing net CFM delivered to the tank\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAudible hissing at tank inlet:\u003c\/strong\u003e Air bypassing the valve seat during pump operation\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eThe Cast Air In-Tank Check Valve Lineup\u003c\/h2\u003e\n\u003cp\u003eCastair offers this valve in multiple inlet and outlet combinations to match different pump and tank configurations. Common sizes in the CTD series (compression fitting inlet, NPT outlet):\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eCTD3838\u003c\/strong\u003e — 3\/8\" compression x 3\/8\" NPT\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCTD3812\u003c\/strong\u003e — 3\/8\" compression x 1\/2\" NPT\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCTD1212\u003c\/strong\u003e — 1\/2\" compression x 1\/2\" NPT\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCTD5812\u003c\/strong\u003e — 5\/8\" compression x 1\/2\" NPT (this part)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCTD1234\u003c\/strong\u003e — 1\/2\" compression x 3\/4\" NPT\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCTD3434\u003c\/strong\u003e — 3\/4\" compression x 3\/4\" NPT\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCTD3410\u003c\/strong\u003e — 3\/4\" compression x 1\" NPT\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCTD1238\u003c\/strong\u003e — 1\/2\" compression x 3\/8\" NPT\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eNPT female inlet versions (CTB series) are also available if your pump uses a female threaded connection rather than a compression tube fitting.\u003c\/p\u003e\n\n\u003ch3\u003eInstallation Notes\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eThread sealant:\u003c\/strong\u003e Use pipe thread sealant on the NPT threads at the tank boss — do not use tape on the compression ferrule side\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTorque carefully:\u003c\/strong\u003e Compression fittings seal with ferrule deformation; overtightening cracks the fitting body\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUnloader port orientation:\u003c\/strong\u003e The 1\/8\" side port faces the unloader tube — verify clearance before fully seating the fitting in the tank boss\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePressure test:\u003c\/strong\u003e After installation, run the compressor to operating pressure and confirm no leak at the fitting joints or through the valve seat at rest\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eTechnical Specifications\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eManufacturer:\u003c\/strong\u003e Castair (Cast Air, Inc.) — Spicer, Minnesota\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePart Number:\u003c\/strong\u003e CTD5812\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eType:\u003c\/strong\u003e In-tank check valve, compression inlet \/ NPT outlet\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eInlet:\u003c\/strong\u003e 5\/8\" compression tube fitting\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOutlet:\u003c\/strong\u003e 1\/2\" NPT male\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUnloader Port:\u003c\/strong\u003e 1\/8\" side port\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMax Working Pressure:\u003c\/strong\u003e 500 PSIG\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMax Temperature:\u003c\/strong\u003e 400 degrees F\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eApplication:\u003c\/strong\u003e Piston-type oil-lubricated air compressors\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhy Buy From Air Compressor Factory Direct?\u003c\/h3\u003e\n\u003cp\u003eWe stock Castair replacement parts alongside their compressors because sourcing OEM components from a third party turns a 20-minute repair into a week-long parts hunt. We know which check valve goes with which pump configuration. If you are not sure whether the CTD5812 is the right fit for your machine, call us — we will verify based on your compressor model before you order. Free shipping on qualifying orders, free technical support, and the full manufacturer warranty on every part we sell.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCall 866-217-0063 for quick answers and help!\u003c\/strong\u003e\u003c\/p\u003e","brand":"Cast Air","offers":[{"title":"Default Title","offer_id":53342535811285,"sku":"CTD5812","price":55.38,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0622\/8466\/0949\/files\/InTankCheckValve_c6af6cb0-013f-4ba6-97ac-338db48ff502.jpg?v=1772652659","url":"https:\/\/aircompressorfactorydirect.com\/products\/castair-5-8x1-2-in-tank-check-valve-compression-tube-fitting-inlet-npt-outlet","provider":"Air Compressor Factory Direct","version":"1.0","type":"link"}