Replacing the Ball Float Valve of Your Water Tank

Two common causes of  water tank leakage are : 1) faulty ball float valve  and  2) crack.

The water tank is constructed with either Polyethylene, GI mild steel or Stainless steel. Whatever the material used, the condition of the tank will deteriorate and crack will appear due to exposure to sun and rain. Water tank kept in an enclosed area will not be subjected to the hazard of the weather and will last much longer.  But GI mild steel tank will leak  even if it is installed in an enclosed place due to rust. This usually occurs after a life span of about seven years

The most common cause of water tank leakage is due to faulty ball float valve. The valve can malfunction due to various reasons. One common problem is small pebbles trapped at the valve washer. This can be easily resolved by pressing the ball float down to let the water pressure flush out the pebbles. Then push the ball float up to check if it shuts the water inflow.  If not, the valve is faulty and need replacement. The other cause is worn out washer/stopper of the valve. This needs the replacement of the valve.

Another rare problem is the ball float cracked,  resulted in water seeping into the ball and lost the ability to float.

The ball float valve works on the simple physic of water level pushing the ball that is attached to a lever that shuts the valve. When the water level rise, the ball is pushed upwards and shuts the valve. When the water level dropped, the ball is lowered and release the valve, allowing water to flow into the tank (see the diagram).

Diagram downloaded from Google and Valmatic.com,

Replacing the ball float valve can be done DIY, provided the water tank is sited at a place that is within easy to reach and has a place for you to stand and work on. This only involve unlocking and locking three nuts. One needs two pairs of pliers, sealing tape and pair of cotton gloves to do the job. 


My water tank is located on the specially constructed roof top, where I can just walk up from a balcony. Not even a ladder is required.

Remember to turn off the incoming pipe before unlocking the nuts from the faulty valve.

This is a new valve 

The two hexagon nuts at the inlet joint of the valve is to secure the valve to the water tank. One nut inside the tank and the other outside. The end of the inlet joint is fastened to the incoming water pipe with a locking nut at it’s end. Before locking the nuts, ensure the sealing tape is wrap round the thread of the joint to prevent leakage.

The ball float valve in the water tank

The ball float valve is readily available at all hardware shops and DIY stores. Depending on your incoming pipe size, the size must be the same. They come in ½ inch, ¾ inch, 1inch and 1 ¼ inch diameter. These are the common sizes used by Malaysian home.

Old valve was dismantled from the water tank.
The float ball is re-used.

The cost of the 1 inch ball valve(minus the ball float) is RM38.00 (USD11.50).

The ball float can be purchased separately at RM2.00 (USD0.60) each.

A roll of sealing tape is only RM0.60 USD0.18)

Total cost to replace the ball float  valve (excluding tool cost) is RM38.60 (USD11.68). If one were to engage a plumber, the charges for materials and workmanship will be at least RM160.00 (USD48.50).  If one is unfortunate to enlist an unscrupulous plumber, one may get cheated to replace the valve unnecessarily.

Old valve for post mortem 

This whole valve replacement job took only two hours to complete.

This  little washer/stopper is the usual problem creator.

It pays to DIY your home maintenance.

These are the only tools and material required to replace the ball float valve. You can try DIY.