✅ This item is normally regularly stocked. Shipping times may vary depending on availability. Please contact us to confirm stock and shipping times. You will receive tracking details once the item has shipped.
Description
LMI AutoPrime Valve For Sale To Stop Sodium Hypochlorite Vapor Lock And Loss Of Prime
The LMI AutoPrime valve is a retrofit accessory that solves the most common LMI pump failure in sodium hypochlorite service, the loss of prime caused by vapor lock. The valve continuously bleeds vapor and a small portion of liquid (10 to 20 percent of pump output) back to the supply tank, keeping the pump primed automatically. It also functions as an air gap anti-siphon device. Field retrofittable to any LMI LiquiPro liquid end on Series A, AA, B, C, J, or P pumps that don't already have an AutoPrime liquid end installed.
What Is Vapor Lock and Why It Kills LMI Pumps
Sodium hypochlorite (the 12.5 percent solution most water treatment facilities use for chlorination) and hydrogen peroxide are unstable. When exposed to heat, light, or normal operating conditions, they decompose and release gas. The gas forms small bubbles inside the pump's suction line and pump head.
LMI diaphragm pumps are positive displacement designs that depend on a continuous liquid column to function. When gas bubbles enter the pump head, the diaphragm compresses the gas instead of pushing liquid, and the pump effectively stops dosing. This is vapor lock. Operators see the symptoms first: dosing inconsistency, the pump running with no chemical flow, and eventually the pump losing prime entirely. Manual venting fixes it temporarily, but vapor returns within hours.
The LMI AutoPrime valve solves vapor lock by adding three working check valves and a return line. Each pump stroke automatically pushes vapor (plus 10 to 20 percent of the liquid) back to the supply tank through a vent. The pump stays primed continuously without operator intervention. For municipalities, this eliminates the labor cost of manual venting (industry case studies cite this cost at thousands of dollars per pump per year). For contractors, it eliminates the after-hours service call.
Key Features of the LMI AutoPrime Valve
- Four working check valves in one assembly. The LMI AutoPrime valve contains a vent check valve, a discharge check valve, an anti-siphon check valve, and a return line. The vent check valve continuously bleeds gas. The discharge check valve regulates pump output. The anti-siphon check valve prevents suction from the supply tank. The return line routes recirculated material back to supply.
- Field retrofittable to any LMI LiquiPro liquid end. Installs by threading clockwise into the existing pump head. No special tools required. No pipe wrench. The AutoPrime valve fits LMI Series A, AA, B, C, J, or P pumps that don't already have an AutoPrime liquid end factory-installed.
- Built for chlorine and peroxide service. Acrylic body, ceramic balls, Viton and Polyprel seats, Hastelloy C spring, and 316 stainless steel fasteners. Every wetted material is selected for sodium hypochlorite and hydrogen peroxide compatibility per LMI's published documentation.
- 300 PSI maximum operating pressure. Handles the full pressure range of all LMI Series A through P pumps without derating. Flow capacity up to 8 GPH (30 L/h) at 5 to 100 strokes per minute, with 30 to 100 percent stroke length adjustment.
- Eliminates the need for a back pressure device. The valve design vents discharge to the atmosphere during each stroke, regulating pump output naturally. This means you save the cost of a separate back pressure valve on most retrofit installations.
- Vertical discharge design. Mounts in the standard vertical orientation that matches LMI's published install diagrams. The return line routes back to the supply tank. The tubing end MUST stay above the highest fluid level in the reservoir (the anti-siphon feature depends on this air gap).
Specifications
| Specification | Detail |
|---|---|
| Product | LMI AutoPrime Valve Assembly |
| SKU (1/4" Acrylic LiquiPro variant) | 38721 |
| Body Material | Acrylic (PVC option available by special order via LMI catalog) |
| Balls and Seat Materials | Ceramic, Viton, PVC, and Polyprel |
| Spring | Hastelloy C |
| Fasteners | 316 stainless steel |
| Flow Range | 0.08 to 5.05 mL per stroke (up to 8 GPH / 30 L/h max pump output) |
| Stroke Rate Compatibility | 5 to 100 strokes per minute |
| Stroke Length Compatibility | 30 to 100 percent |
| Maximum Operating Pressure | 300 PSI |
| Recirculation Rate | Approximately 10 to 20 percent of pump output back to supply |
| Compatible Pump Series | LMI Series A, AA, B, C, J, P (LiquiPro liquid ends only, retrofit) |
| NOT Compatible With | Flooded suction installations. Pumps that already have an AutoPrime liquid end factory-installed. |
| Discharge Connection | No fitting on the discharge side. Designed for use with LMI Multifunction Valve (sold separately). |
| Trademark | AutoPrime is a trademark of Milton Roy Company |
| Manufacturer | LMI (Milton Roy), Ivyland, PA, USA |
Will This Fit My Pump?
Match your LMI pump's series and liquid end type to confirm the LMI AutoPrime valve will retrofit your existing setup:
| Your Pump | Your Liquid End | AutoPrime Valve Fit | Capacity Notes |
|---|---|---|---|
| LMI Roytronic Series A | PVC or Acrylic LiquiPro | Compatible (retrofit) | 0.001 to 1.7 GPH range |
| LMI Series AA | PVC or Acrylic LiquiPro | Compatible (retrofit) | 0 to 1.85 GPH range |
| LMI Series B | PVC or Acrylic LiquiPro | Compatible (retrofit) | 0 to 3.5 GPH range |
| LMI Series C | PVC or Acrylic LiquiPro | Compatible (retrofit) | 0 to 2.5 GPH range |
| LMI Series J | LiquiPro variants | Compatible (retrofit) | Confirm pump model with our team |
| LMI Roytronic Series P | PVC or Acrylic LiquiPro | Compatible (retrofit) | 0.003 to 1.85 GPH range |
| Any LMI pump with AutoPrime liquid end already installed | AutoPrime factory-installed | NOT compatible (already has it) | No retrofit needed |
| Any LMI pump in flooded suction installation | Any liquid end | NOT compatible (flooded suction) | Use standard liquid end instead |
Not sure which liquid end your pump has? Contact our team with your LMI pump's complete model number and we'll confirm compatibility before you order. LiquiPro liquid ends carry the prefix "LP" on the pump label.
Installation Quick Reference
Full installation procedure is in the LMI AutoPrime Valve Information Sheet (Form 1962.G 7/04) linked on this page. Quick reference for installers planning the retrofit:
- Verify the O-ring seal at the bottom of the AutoPrime valve is in place before installing.
- Thread clockwise into the pump head until it bottoms firmly. DO NOT use a pipe wrench or tools (per LMI's published instructions, tool tightening will damage the O-ring seal).
- Connect the return line tubing to the AutoPrime valve. Route the tubing back to the solution reservoir. The tubing end MUST stay above the highest fluid level. This air gap is what makes the anti-siphon feature function.
- Vent the return line to the atmosphere. Do NOT submerge the return tubing end. The valve will not function if the return line is sealed or submerged.
- Connect remaining suction and discharge tubing before startup. The discharge side has no fitting on the AutoPrime valve itself, this is by design (use the LMI Multifunction Valve on the discharge side, sold separately).
- Start the pump at 100 percent stroke and 100 percent speed. The pump is primed when the solution begins to exit the return line. Once primed, reduce pump settings to your dosing target.
What's In the Box
- LMI AutoPrime Valve assembly (1/4 inch tubing, Acrylic body, LiquiPro family, SKU 38721)
- Factory-installed O-ring seal at the valve base
- LMI Form 1962.G AutoPrime Valve Information Sheet (installation and operation instructions)
NOT included (sold separately): Return line tubing (operator-supplied, typical 1/4 inch OD polyethylene), LMI Multifunction Valve for the discharge side (designed to pair with the AutoPrime, sold by Cleanflow), and any LiquiPro liquid end retrofit kit if your pump doesn't already have a LiquiPro head.
Why Buy the LMI AutoPrime Valve From Cleanflow
Cleanflow Utility Supply Company is an authorized LMI distributor based in Winnipeg, Manitoba. The LMI AutoPrime valve ships from our Canadian warehouse with free shipping on orders over $199 CAD, no cross-border customs delays, no currency exchange surprises. Canadian utilities, contractors, and treatment facilities get the genuine LMI factory product backed by the LMI manufacturer warranty plus Cleanflow's 30-day return window. When you need to retrofit multiple pumps in one project, the LMI AutoPrime valve volume discount pays for itself.
Buy LMI AutoPrime Valve Online from Cleanflow
Stop fighting vapor lock manually. Add the LMI AutoPrime valve to your cart and your order ships free across Canada on totals over $199 CAD. In stock now from Cleanflow's Winnipeg warehouse. Browse the LMI Multifunction Valve (designed to pair with AutoPrime on the discharge side) or the full LMI Pump Repair Parts catalog to complete your retrofit.
Frequently Asked Questions
Will the LMI AutoPrime valve fit my pump?
The LMI AutoPrime valve retrofits any LMI Series A, AA, B, C, J, or P pump that uses a LiquiPro liquid end and that does NOT already have an AutoPrime liquid end factory-installed. If you're not sure which liquid end your pump has, check for the prefix "LP" on the pump label, or contact our team with your full pump model number and we'll confirm compatibility before you order.
How do I know if my pump has vapor lock?
Common symptoms include: the pump runs but no chemical flows, dosing rate is inconsistent or drops to zero, you hear the diaphragm cycling but see bubbles in the suction line, or the pump primes initially then loses prime within hours. Vapor lock happens fastest in warm weather, in pumps mounted above the chemical supply, and in long suction lines. If you're manually venting your pump more than once a week, the LMI AutoPrime valve will eliminate that maintenance step.
Why doesn't the LMI AutoPrime valve work in flooded suction installations?
The AutoPrime valve relies on the suction side being below the supply tank's chemical level (suction lift configuration), so the vent check valve can release vapor upward through the return line. In a flooded suction installation (where the supply tank is above the pump), gravity already keeps the pump primed and the AutoPrime's vent mechanism doesn't work correctly. For flooded suction installations, use the standard LMI liquid end without an AutoPrime valve.
What's the difference between the AutoPrime valve and an AutoPrime liquid end?
The AutoPrime valve is a retrofit accessory that threads into the existing pump head. It adds AutoPrime functionality to a pump that doesn't already have it. An AutoPrime liquid end is the complete pump head that ships factory-installed with AutoPrime built in (for example, the LMI C HI Series pump). If you're buying a new pump for sodium hypochlorite service, get a pump with the AutoPrime liquid end factory-installed. If you have an existing pump losing prime, retrofit it with the AutoPrime valve.
Does the LMI AutoPrime valve come with the multifunction valve?
No. The AutoPrime valve has no fitting on the discharge side because it is designed to pair with the LMI Multifunction Valve sold separately. The Multifunction Valve provides anti-syphon, pressure relief, line drain, and priming aid functions on the discharge side, completing the retrofit. Cleanflow stocks the LMI Multifunction Valve. Most operators order both together.
Is the LMI AutoPrime valve NSF certified for drinking water service?
LMI's 2004 product information sheet listed the AutoPrime valve as "NSF Approval Pending." For the current NSF certification status, contact our team and we will check directly with LMI on the latest certification documentation. The wetted materials (Acrylic, Ceramic, Viton, PVC, Polyprel, Hastelloy C, 316 stainless steel) are all standard materials used across LMI's potable water product line, but formal NSF documentation should be confirmed before specification for municipal procurement.
Can I install the LMI AutoPrime valve myself?
Yes, with basic plumbing experience. Thread the valve clockwise into your existing pump head until it bottoms firmly (hand-tight only, do NOT use a pipe wrench). Connect the return line tubing and route it back to the supply tank with the tubing end above the highest chemical level. Start the pump at 100 percent stroke and speed until the solution exits the return line, then dial back to your dosing target. Total install time is typically under 20 minutes.
How much chemical does the AutoPrime valve waste through recirculation?
The LMI AutoPrime valve recirculates approximately 10 to 20 percent of the pump's output back to the supply tank. This is not waste, the recirculated chemical goes back to your supply and gets pumped on the next cycle. The net effect is your pump's effective dosing capacity is 80 to 90 percent of its nameplate rating. When sizing a retrofit, account for this by setting the pump 10 to 20 percent above your target dose rate.
What is Cleanflow's return policy and warranty on the LMI AutoPrime valve?
Cleanflow offers a 30-day return policy on the LMI AutoPrime valve. Submit returns or exchanges through our portal at returns.cleanflow.net. The product also carries the LMI manufacturer warranty against defects in materials and workmanship. Keep the original packaging and your order confirmation for any warranty claim. For questions about warranty coverage or to start a return, contact our team at [email protected] or 1-866-335-1078.
✅ This item is normally regularly stocked. Shipping times may vary depending on availability. Please contact us to confirm stock and shipping times. You will receive tracking details once the item has shipped.
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