# Water Tank Overflowing? Float Valve Problems | KL1 Plumber > Water pouring from the overflow pipe? Ball float valve failure, the overflow pipe URL: https://kl1plumber.com/guide/water-tank-overflowing-float-valve/ Last-Modified: 2026-10-07 Tags: water tank overflowing, float valve problem, ball valve tank, overflow pipe running Guides # Water Tank Overflowing? Float Valve Problems Explained Water pouring from the overflow pipe? Ball float valve failure, the overflow pipe's role, water wastage, and repair vs replacement. Updated 7 October 2026 4 min read Reviewed by KL1 Plumber's licensed team ![Water running from a roof tank overflow pipe](https://placehold.co/1200x630/0B132B/FFFFFF?text=Water+running+from+a+roof+tank+overflow+pipe+on+the+side+of+a+terrace+house) ## Why Is My Water Tank Overflowing? If you see water dripping or pouring from a small pipe sticking out under the eaves, your roof tank is filling past its normal level. The most common reason for a water tank overflowing is a faulty float valve. Our team at KL1 Plumber, operating under Hong Seng Plumbing, handles these calls constantly across Kuala Lumpur. A quick repair here is one of the most worthwhile fixes in our water tank services [/water-tank-services/ →](/water-tank-services/) , because it stops immediate waste. We will walk through exactly what fails, how much it is costing you, and the fastest way to get it sorted out. ## How the Float Valve Works ![Brass ball float valve inside a water tank](https://placehold.co/800x500/1C2541/FFFFFF?text=Brass+ball+float+valve+with+arm+and+float+inside+a+water+tank) The ball float valve sits directly on the inlet pipe inside the tank to control the incoming water supply. It uses a floating ball on a lever arm to shut off incoming water once a specific level is reached. We often see standard half-inch brass valves installed in most Malaysian homes. When the tank is full, the arm pushes a washer against the valve seat to shut off the main flow. Our technicians always check the mechanical arm alignment during a routine inspection. As you use water in your bathrooms, the level drops, causing the float to fall and reopen the valve for a refill. A standard valve setup includes three main parts: - **The Valve Body:** The main brass or heavy-duty plastic housing connected to your incoming pipe. - **The Lever Arm:** A sturdy metal or plastic rod that transfers movement. - **The Float Ball:** A hollow sphere that sits directly on top of the water surface. ## What the Overflow Pipe Does The overflow pipe is a vital safety outlet set just above the normal water level inside the tank. If the float valve fails, excess water escapes through this overflow pipe instead of spilling into your ceiling space. Our building standards in Kuala Lumpur typically dictate using a 15mm or 20mm white PVC pipe for this outlet. An overflowing pipe is technically doing its job to protect your property from structural water damage. We always remind customers that a dripping pipe is a clear alarm bell indicating the internal valve has a problem. ### Where Does the Water Go? You will usually see this drainage pipe protruding from the side of your house or directly under the roof eaves. Sometimes builders route it directly down into a roof gutter, making a slow leak much harder to spot right away. ## Common Float Valve Faults A float valve problem usually comes down to degraded internal washers, debris blocking the seal, or physical damage to the float ball. These moving parts sit completely submerged and simply wear out after several years of constant use. We frequently find small stones or sediment trapped in the valve seat after Air Selangor conducts main pipe repairs in a local neighborhood. The table below outlines the most frequent issues. | Fault | What happens | | --- | --- | | Worn or hardened rubber washer | Valve cannot seal properly; water trickles in constantly | | Scale or grit on the brass valve seat | Washer cannot close fully against the metal | | Cracked or waterlogged float ball | Float sinks under the water line and never shuts the valve | | Bent or stiff lever arm | Float rises normally but the mechanical arm does not close the valve | | Water level set too high | Tank fills to just above the overflow pipe threshold | | High municipal mains pressure | Pressure violently forces water past an otherwise decent valve | ## How Much Water Does It Waste? Overflow water goes straight to the drain or splashes onto your property, wasting hundreds of liters a day. A stuck ball valve tank can waste anywhere from 300 to over 1,000 liters of water every single day. Our experience shows a stuck valve can easily push a household into the highest water tariff bracket. All of this wasted water passes through your meter first, meaning you pay for every single drop. We recommend checking this immediately if your monthly utility bill has suddenly spiked. The current Air Selangor domestic tariff jumps to RM2.00 per cubic meter once your household exceeds 35 cubic meters. Our comprehensive guide to a high Air Selangor bill [/guide/high-water-bill-hidden-leak/ →](/guide/high-water-bill-hidden-leak/) lists several other common culprits to investigate. > **Quick check from outside** > > Look at the overflow pipe in the early morning, when nobody has used water for hours. If it is dripping or running then, the float valve is not shutting off. ## Repair or Replace the Valve? ![Plumber replacing a worn float valve washer](https://placehold.co/800x500/F8FAFC/0B132B?text=Plumber+replacing+a+worn+float+valve+washer+on+a+tank+inlet+in+a+roof+space) Deciding whether to repair or replace depends entirely on the physical condition of the main valve body. You can repair a unit when the brass or plastic body is sound by replacing the washer, cleaning the seat, or adjusting the arm. We usually replace the entire assembly when the valve is heavily corroded or keeps failing repeatedly. A new brass or heavy-duty plastic float valve is an inexpensive part, typically costing between RM15 and RM45 locally. Our customers find that replacing it outright often costs little more in labor than attempting to repair an old, brittle one. ### Our Standard Tank Inspection While we are up at the roof tank, we perform a few extra checks to ensure long-term reliability. A complete service visit includes: - **Clearing the overflow pipe:** Ensuring wasp nests or debris do not block the safety exit. - **Checking for sediment:** Removing grit from the tank floor that could quickly damage the new valve. - **Inspecting fittings:** Looking for slow leaks at the main inlet and outlet connections. ## Is It Safe to Wait? An overflow pipe running is not an immediate emergency if the water is draining safely outside your home. You can technically wait a day or two, but it wastes valuable treated water and money every single hour. We tell homeowners to treat the situation as urgent if the overflow pipe appears blocked or damaged. Water spilling directly into the ceiling space will quickly ruin plasterboard ceilings and electrical wiring. Our best advice in that critical scenario is to immediately close the main inlet valve supplying the roof tank. ## Book a Fix You can schedule a professional plumber to resolve your water tank overflowing issues quickly and permanently. Fixing a ball valve tank is a straightforward job that restores peace of mind and normal utility bills. Our standard troubleshooting visit is RM30 and is completely waived when you approve the final quote. Float valve repairs and total replacements are quoted fairly on site before any work begins. We can even flush and clean the entire tank [/guide/how-often-clean-water-tank/ →](/guide/how-often-clean-water-tank/) during the same visit if the water quality looks poor. Contact us today to get your home plumbing back to normal. ## Learn more about Water Tank Services See how KL1 Plumber handles this in Kuala Lumpur and the Klang Valley, what it costs to check, and what happens next. View service [/water-tank-services/ →](/water-tank-services/) FAQ ## Quick Answers Common questions about water tank overflowing. ### Why is water coming from my overflow pipe? The float valve is not shutting off the inlet when the tank is full, so water keeps flowing in and escapes through the overflow pipe. ### Can I adjust the float myself? Sometimes, if the tank is safe to reach and the valve has an adjustment screw. A worn washer, cracked float or bent arm needs repair or replacement. ### Does overflow raise my bill? Yes. Overflowing water runs into the drain continuously and is metered, so a constantly running overflow adds to your water bill. ### Still have a question? Send us a photo of the problem on WhatsApp and we will tell you what it likely is and what it costs to check. WhatsApp a Photo [https://wa.me/60105260000?text=Hi%20KL1%20Plumber%2C%20I%20need%20a%20quote →](https://wa.me/60105260000?text=Hi%20KL1%20Plumber%2C%20I%20need%20a%20quote) +6010-526 0000 [tel:+60105260000 →](tel:+60105260000)