RO Solenoid Valve (SV): What It Does, Signs of Failure and How to Replace

The solenoid valve (SV) is a small electric valve, usually on the inlet side of your RO. It opens when the purifier is running and closes when the purifier stops. A faulty SV is one of the most common – and cheapest – RO problems to fix.

What does the solenoid valve do?

Most RO solenoid valves are 24V DC, normally closed. When the purifier switches on, the SV gets power and opens so water can flow to the pump and membrane. When the tank is full or the power goes off, the SV closes and stops water from flowing through – and draining away – while the purifier is idle.

5 signs of a faulty solenoid valve

1. Water keeps flowing to the drain even when the purifier is off or the tank is full – the SV is stuck open.
2. No water enters the purifier though the pump hums – the SV is stuck closed or its coil has burnt out.
3. Tank overflows in purifiers where the SV should shut off the supply.
4. Clicking or buzzing without any flow.
5. Visible leak from the SV body or its joints.

Simple checks

• Power: make sure the SV is getting 24V when the purifier is running (check the SMPS and connector).
• Dirt: sand from the inlet can block the tiny orifice. A choked sediment filter lets dirt through – replace it.
• Direction: the arrow on the SV body must point in the direction of water flow.
• Swap test: if you have a known-good SV, swapping it in is the quickest test.

How to replace the SV

1. Unplug the purifier and close the inlet valve.
2. Note which pipe goes in and which comes out (follow the arrow).
3. Pull the wire connector off the SV.
4. Release the pipes from the push-fit ends (press the collet ring and pull).
5. Fit the new SV with the arrow in the flow direction, push both pipes in fully and reconnect the wires.
6. Open the inlet, switch on and check for leaks. Then switch off and confirm no water goes to the drain.

Choosing the right SV

Match the voltage (almost all domestic ROs use 24V DC) and the connection type – 1/4 inch quick-fit push-in ends are most common in domestic purifiers, while some use threaded 1/2 inch ends. See all RO solenoid valves (from ₹180).

Frequently asked questions

Why is my RO wasting water when switched off?

The most common reason is a solenoid valve stuck open. Replacing the SV usually fixes it.

Can I run an RO without a solenoid valve?

It is not recommended. Without the SV, water keeps flowing through the membrane to the drain when the purifier is idle.

Is the RO solenoid valve AC or DC?

Domestic RO solenoid valves are almost always 24V DC, powered from the same SMPS as the pump.

Need help choosing the right part? Send a photo of your RO or its model name on WhatsApp (96252 23245) and we will tell you exactly what fits.