Water Tank Overflowing? How to Fix or Replace a Float Valve (Ball Valve) 2026

Oct 18, 2026

Buy More Mall Kenya

A tank that overflows wastes water, raises the bill and can soak walls and ceilings. In most cases the cause is a float (ball) valve that no longer shuts off. It is a cheap part and usually a 30-minute fix.

Quick answer: A float valve closes the inlet when the float rises with the water. If the tank overflows, adjust the float arm down so it shuts off lower, clean or replace the washer if water still passes, or replace the whole valve if the float is cracked or the body is worn. Match the size to the inlet pipe: 1/2" (KSh 650) or 3/4" (KSh 900) on Buy More Mall. Always keep the overflow pipe clear.

How a Float Valve Works

The float sits on the water surface on an arm. As the tank fills, the float lifts the arm, which pushes a washer against the inlet and stops the flow. When water is used, the float drops and the valve opens again.

Float Valves on Buy More Mall

Ball Valve-Tank 1/2 – price in Kenya — Ball Valve-Tank 1/2
**KSh 650**

Ball Valve-Tank 3/4 – price in Kenya — Ball Valve-Tank 3/4
**KSh 900**

Ball Valve-Cistern – price in Kenya — Ball Valve-Cistern
**KSh 350**

Ball Valve-Toilet – price in Kenya — Ball Valve-Toilet
**KSh 350**

Ball Valve Low Pressure – price in Kenya — Ball Valve Low Pressure
**KSh 250**

Thread Tapes Big – price in Kenya — Thread Tapes Big
**KSh 150**

Some photos are reference images of the product type, used under open licences. Image credits are on each product page.

Valve	Use	Price
Ball Valve-Tank 1/2	Tank inlet 1/2"	KSh 650
Ball Valve-Tank 3/4	Tank inlet 3/4"	KSh 900
Ball Valve Low Pressure	Low-pressure supply	KSh 250
Ball Valve-Cistern	Toilet cistern	KSh 350
Ball Valve-Toilet	Toilet	KSh 350
Thread Tapes Big	Thread tape for the connection	KSh 150

Why Is My Tank Overflowing?

Cause	Fix
Float set too high	Bend or adjust the arm so it closes about 5 cm below the overflow
Worn or dirty washer	Turn off the supply, open the valve, clean or replace the washer
Cracked float full of water	Replace the float or the whole valve
High mains pressure	Fit a valve rated for the pressure
Pump not switching off	Check the float switch or controller (see pump controllers)

How to Replace a Tank Float Valve

Turn off the supply to the tank (mains stop valve or pump).
Undo the inlet pipe connection at the valve.
Unscrew the back nut and remove the old valve from the tank wall.
Fit the new valve with washers on both sides of the tank wall; hand-tighten then a quarter turn.
Wrap thread tape on threaded connections and reconnect the pipe.
Turn the water on and set the float so it shuts about 5 cm below the overflow.
Watch one full fill and check for drips.

Do Not Forget the Overflow

Every tank needs an overflow pipe that discharges where you can see it. A dripping overflow is an early warning that the float valve needs attention. For cleaning and installation tips see how to clean a water tank and how to install a water tank.

Worked Example: A Roof Tank Overflowing at Night

A family notices water running off the roof every night when mains pressure is high. The float valve washer is worn. They shut the supply, replace the 1/2" float valve, set the float lower and the overflow stops.

Common Mistakes to Avoid

Tying the float arm up with wire as a "fix".
Wrong size valve for the inlet pipe.
Blocked or missing overflow pipe.
Over-tightening plastic tank fittings.

Not sure which one fits? Send us your details on WhatsApp or through the product page and we will help you choose.

Frequently Asked Questions

Why is my water tank overflowing?

Usually the float valve is set too high or its washer is worn.

How does a float valve work?

A float lifts an arm that closes the inlet as the water rises.

How much is a float valve in Kenya?

From KSh 650 for a 1/2" tank float valve on Buy More Mall.

Can a float valve be repaired?

Often yes, by adjusting the arm or replacing the washer; a cracked float needs replacement.

What size float valve do I need?

The same size as the inlet pipe, usually 1/2" or 3/4".

Prices shown are regular prices on Buy More Mall. Many products are currently on offer, so open the product page to see today's price.

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