Solenoid Dosing Pump Installation: Foot Valve, Injection Valve and Vent Line

Solenoid dosing pump installation is not heavy work. The pump is small and light and fixes to a wall or bracket with a few screws. What decides whether it doses reliably are three small parts supplied with it: the foot valve at the end of the suction line, the injection valve at the dosing point, and the vent line from the pump head. The foot valve filters and stops the suction line draining. The injection valve stops siphoning and backflow from the process. The vent line takes gas from the head back to the tank. Fit all three correctly and most "no dosing" and "wrong dose" complaints never happen.

This guide is written for operators and installers who carry out solenoid dosing pump installation on water treatment, cooling water and small chemical duties.

Before solenoid dosing pump installation

Check a few things first:

• Pump flow and pressure suit the duty; see solenoid metering pump selection.
• Positions of tank, pump and injection point, with the shortest practical suction line.
• Supply voltage and earth, and where control and level switch cables will connect.
• Tubing compatible with the chemical. Supplied tubing is usually matched, so do not swap it casually.

Mount the pump beside the tank with its inlet at or below tank level where possible. A flooded suction is the most reliable arrangement. Follow the manual for any height limits.

Foot valve in solenoid dosing pump installation: pointing down

A foot valve is a check valve with a strainer, fitted to the end of the suction tubing and sitting in the tank. It keeps debris out of the pump and stops the suction line draining back when the pump stops.

Installation points:

1. Hang the foot valve vertically, pointing down, a short distance above the tank floor so it does not draw sediment.
2. Weight or clamp it so it cannot float or tip.
3. Clean the strainer regularly; PAC and sodium hypochlorite crystallise on it.

Laying the foot valve flat on the tank floor is a common shortcut. The strainer soon blocks with sediment and the pump gradually loses prime. The check valve inside has a direction like those in the pump head; see check valve function and installation direction.

Injection valve: the last barrier in solenoid dosing pump installation

The injection valve sits at the end of the discharge tubing and enters the process pipe or tank. Inside is a spring-loaded check valve that:

• Lets chemical flow only from pump to process, so process water cannot run back up the dosing line.
• Adds an opening pressure that acts a little like a back pressure valve and reduces siphoning.

Direction and position

Enter the process pipe from the bottom or side, pointing up or horizontal. Avoid entering from the top, where gas collects at the valve. Insert far enough that chemical enters the main flow.

The spring pressure in an injection valve is limited. When dosing into an open tank, or when the pump outlet is below the tank liquid level, it may not stop siphoning on its own. Add a separate back pressure valve; see why metering pumps need a back pressure valve.

The valve tip is in contact with process water and scales up first. On hard water and hypochlorite duties, remove and clean it on a schedule, or discharge pressure will creep up.

Vent line: the most overlooked part of solenoid dosing pump installation

Most solenoid pump heads have a bleed or vent valve with a small tube attached. During priming and in operation, gas and a little chemical leave through it.

1. In solenoid dosing pump installation, route the vent line back to the tank, ending above the liquid surface, never below it.
2. Avoid upward loops that hold liquid.
3. Do not leave it on the floor or run it to a drain, where drips damage equipment.

With gassing chemicals such as hypochlorite and hydrogen peroxide, the vent works hard, so its routing matters even more.

Solenoid dosing pump installation: mounting, wiring and testing

Mounting. In any solenoid dosing pump installation, fix the pump level on a wall or bracket with the head facing the service side. Avoid direct sun and places where chemical can drip onto it.

Wiring. Isolate power first. Connect power, external control and level switch to their own plugs and make sure the earth is sound.

Test sequence:

1. Run on clean water first.
2. Start at low stroke and frequency, open the vent valve until liquid runs without bubbles, then close it.
3. Check foot valve, pump inlet, pump outlet and injection valve joints for leaks.
4. Bring settings up to target and calibrate actual output.

Safety: once chemical is in the system, stop the pump and relieve pressure before opening any joint, and wear gloves and eye protection. Always isolate power before wiring.

A well-made pump comes with matched accessories, so the foot valve, injection valve, vent tubing and hoses suit the head material and chemical. Browse more models under solenoid diaphragm metering pumps.

Conclusion

Good solenoid dosing pump installation depends on three small parts. Hang the foot valve pointing down, clear of the floor, and clean it often. Enter the process from below or the side with the injection valve, and add a back pressure valve for open tanks. Return the vent line to the tank above the liquid. Mount the pump firmly, wire it with power isolated, test on water, prime first and then set the flow. Tell us about your dosing point and chemical, and contact our engineers to confirm the right accessories.

FAQ

Can solenoid dosing pump installation skip the foot valve?

It is not recommended. Without it, the suction line can drain after each stop and the pump must prime again, and tank debris goes straight into the head.

Can the injection valve replace a back pressure valve?

Sometimes. It has a modest opening pressure, but for open tanks or a large height difference it may not stop siphoning, so fit a separate back pressure valve.

Why must the vent line end above the liquid?

Below the surface it creates back pressure, venting slows, and chemical can siphon back into the head.

What makes a good accessory kit for solenoid dosing pump installation?

Parts made from the same material as the head, strainers, springs and seals that resist the chemical, and tubing sized to the fittings so nothing needs adapting on site.

Can solenoid dosing pump installation put the pump above the tank?

Yes, within its suction lift, as long as the foot valve seals well and the pump is fully primed at start-up. A flooded suction is still more stable.