Omnia Mechanical Group

571 Timpson Place Bronx, NY 10455

Phone: 212-534-2500

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What Causes a Toilet To Run Intermittently?

Multi-family or multi-unit properties can experience their fair share of plumbing issues because of the number of bathrooms and consistent use of plumbing supply and waste lines. As a landlord, you have likely experienced several complaints or service requests about a toilet running intermittently. Most times, the culprit behind the intermittent running is a slow leak from the tank to the bowl. Unfortunately, that is not the only cause; some issues are more costly and severe than others. Still, have no fear because Sanitary Plumbing is here to save the day and explain.

7 Reasons for Your Toilet Running Intermittently

1. Faulty Flapper

The flapper is the rubber seal or device at the bottom of your tank that covers the flush valve opening. The flapper chain connects the flapper to the toilet handle, so when the handle gets pressed, the chain lifts the flapper from the valve, forcing water to empty from the tank to the bowl. After the flush, when the tank empties, the flapper settles back over the flush valve, creating a watertight seal and allowing the tank to refill.

If a toilet randomly runs, the likely issue is a faulty or warn flapper. Long-term use can wear down the rubber or cause warping. Also, mineral deposits can build up around the edge of the flapper, forcing it to sit askew over the flush valve. Any of these issues can allow a small gap around the seal, permitting the tank to empty slowly, resulting in a toilet running intermittently.

2. Incorrect Float Setting

The float is a device inside the toilet tank that senses the water level and connects to the fill valve or refill mechanism. Typically, the float is ball-shaped, but some toilets have cylindrical cup designs. As the water level in the tank drops, the float lowers, triggering the fill valve to replenish the tank.

High float settings may allow water to continue filling the tank past the top of the overflow tube, meaning the float valve never engages the shutoff for the fill valve. This is a silent leak because water goes directly down the drain, continuously triggering the refill cycle.

3. Misaligned or Tangled Flapper Chain

The flapper chain extends from the flush handle’s lever arm to the rubber flapper. Pressing the handle should pull the chain taunt, lifting the flapper and beginning the flushing cycle. In an ideal operation, when the tank empties, the lever arm, flapper chain, and flapper should return to their original positions.

That said, a flapper chain can be too short or too long. If it is too short, the chain may interfere with the flapper seal over the flush valve, allowing a slow leak into the bowl, resulting in a toilet running intermittently. If the chain is too long, it can bunch up, tangle, or get caught under the flapper, again, resulting in a slow leak.

4. Fill Valve Problems

The fill valve is the device or mechanism that controls how water refills the tank after a flush. The mechanism usually comprises a vertical assembly with a float, a connector from the water supply line, and a refill tube that directs water to the overflow tube.

There are several reasons a fill valve may cause intermittent running water. Hard water or sediment can cause clogs within the fill valve, impeding its ability to seal off the water supply and leading to overfilling. Worn seals or damage to moving parts can affect the water control mechanisms, leading to leaking and overfilling. Also, incorrect refill volume or float height adjustments can cause too much or too little water in the tank.

5. Worn or Damaged Flush Seal

The flush valve is the large opening at the base of the toilet tank that allows water to flow into the bowl when the flapper lifts, breaking the seal. The flush valve seal is a large rubber gasket around the opening. With the flapper, this seal creates a watertight seal when the toilet is at rest.

A toilet running intermittently could mean deterioration or damage to the flush seal. Damage can occur because of poor water quality, mineral deposits, or age. Typically, a seal should last five to seven years, depending on usage and water quality.

6. Cracks in the Tank or Bowl

Thankfully, cracks in toilet tanks and bowls are relatively uncommon. Porcelain toilets are solid and designed to handle excessive weight and pressure from regular use. Still, impact damage, manufacturer defects, extreme temperature shifts, and incorrect installation can lead to hairline cracks or fractures. Even hairline cracks can cause enough of a leak to cause intermittent running.

If you find a crack in a toilet on your property, it is best to replace it. While some repair options exist, the fixes are usually not permanent and offer no guarantees. Sanitary Plumbing can help you assess the damage and determine the best course of action.

7. Water Supply Line Issues

The supply line is the flexible hose that connects to the water shutoff valve from the wall to the underside of your toilet. There are several issues with the supply line that can cause intermittent running water. Leaks in the line can prevent the fill line from shutting off. Thankfully, most leaks are easy to spot because you may see puddles under the line or near the toilet’s base. The problem is that some leaks occur inside the wall, making access challenging.

Kinks and blockages can restrict water flow to the toilet. Twists, bends, or clogs can affect how quickly the tank fills or prohibit filling altogether.

A faulty shutoff valve can mimic water supply line issues. This problem is obvious when you close the valve, but the intermittent running continues.

How Sanitary Plumbing Can Help With a Toilet Running Intermittently

Licensed Plumbers Are Always Available

Does your building have a toilet running intermittently? Have you ruled out any likely culprits? Sanitary Plumbing is always available to help you solve your plumbing mysteries. Call us at 212-734-5000 to schedule an inspection or inquire about the benefits of regular maintenance.

Our Privacy Policy

Omnia Mechanical Group(the “Company”) strives to ensure the highest standards for property listings and customer information privacy. Please review the following statement to learn about our company practices and policies. Please be aware that our Privacy Policy is subject to change at any time.

1. Purpose.

This Privacy Policy (“the Policy”) provides information on how the Company uses your personal information. By agreeing to the Policy, you agree to our collection and use of your personal information as described in the Policy. This Privacy Policy is effective for all new users of

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You can browse some areas of (“the Website”) without being a registered user. However, certain activities do require registration. (You consent to the transfer and storage of your information by registering with

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Our primary purpose in collecting personal information is to provide you with a safe and user-friendly experience. For example, the Company may use your personal information to:

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We may occasionally ask you to complete optional surveys. These surveys are used to improve and customize your experience with

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The Company does not share any of your personal information with outside organizations, companies, individuals, etc. The only exception to this standard is if such a disclosure is reasonably necessary to respond to any and all legal processes.

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The Company provides you with the opportunity to opt-out of receiving promotional and other non-essential, marketing-related communications from Omnia Mechanical Group. If you would like to opt-out of these select communications, please see any of the Company’s email communications and follow the directions indicated.

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The Company does not guarantee the accuracy of information for any and all of its properties on the Website, and is not responsible for any errors or misrepresentations (made by Renters, the Client, or otherwise).

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We may amend this Privacy Policy at any time by posting the amended terms on the Website. All amended terms are immediately effective after they are initially posted on the Website.

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