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Leak at Commode Tank

I have a commode in my home which the tank tops off about every 30 minutes or so. It doesn't run water very long, but is annoying. This commode has a vertical plunger which seals against a rubber seal at the bottom outlet of the tank. The plunger is activated by the flush handle on the exterior of the tank.I have cleaned the tank around the seal, replaced the rubber seal and plunger, but the problem stills exists. I would appreciate any suggestions. Thanks

Re: Leak at Commode Tank

Could be a leak in the overflow stand pipe.

Re: Leak at Commode Tank

Possibly another thing to check...

Depending on how the flush handle is attached to the plunger ( flapper ) ... does it use a rod or chain that might need an adjustment? It might be restricting the closure of the flapper if out of adjustment and allowing a slight amount of water leaking from the tank. After 30 minutes there may be just enough leakage to drop the water level to open the float shut off valve.

Re: Leak at Commode Tank

I would definitely check the points made by canuk & Jack first to see if this solves the problem.

If these don't clear up the problem, keep at it; working on toilets is frustrating, but try to isolate the source of the leak; there may be other causes (especially if the parts are quite old), so you have to check out each one.

Even a small leak will cost you big bucks with wasted water, which shows up on your quarterly water bill.

Take a strong light & examine the underparts of the tank & bowl to make sure there is no water present.

As canuk mentioned, the guide arm, lower lift wire & upper lift wire & chain must be adjusted properly so the tank ball seats solidly on the valve seat.

As Jack mentioned, there is an overflow tube that sometimes corrodes & develops a silent leak; take a flashlight & shine it down the tube to see if you see a leak; this may be so slight as to appear as a "vein" alongside the tube housing.

There is also a bowl refill tube that feeds into the overflow tube; some water could continue leaking out of this tube if the ballcock valve is defective.

There's an outside chance you have a "cross connection" in your water supply piping due to a defective ballcock valve.

When this exists, every time you open another faucet in the house, the house water pressure drops & toilet tank water is siphoned into the water system, dropping the water level slightly in the tank.

These possibilities can be checked by closing the shut off valve under the toilet after each toilet use & taking a magic marker & marking the tank water level inside the tank.

If the level remains the same with the
shut-off valve closed, the problem is not the discharge valve seat.

If you still have a leak, plumbing supply stores have an inflatable rubber hose you can insert into the valve seat & inflate with a tire pump to test for discharge tube leakage.

A box of mortite(Home Depot/Lowe's/hardware stores) can be made into a large ball (heat slightly in a VERY LOW oven if needed).

This can be firmly fitted over the valve seat to temporarily seal it to see if this stops the leak.

The mortite ball must be fitted around a string with a stopper tied to the bottom to prevent the mortite from accidently falling down the drain.

Refill the tank & see if this stops the leak; if it does, there is a distortion in the valve seat or tank ball, or a hairline crack in the valve seat.

The toiletology site below has a list of other troubleshooting tips for flush valves.

At the toiletology site, scroll down until you get to the red schoolhouse; click onto the red schoolhouse, then the Index, then "fixing flush valve"

The other sites are helpful to understand the toilet parts.

There is an epoxy glue-on kit that can be used to replace the tank ball with a flapper; flappers are usually more reliable.

If the ballcock valve is defective, they are usually replaced with a 400 series Fluidmaster anti-siphon floating cup ballcock ($5 at Home Depot/Lowe's).

Brass ballcocks cost a fortune these days, due to the big jump in copper prices; ballcocks can be repaired if the exact washer kit can be found.


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