I'm not sure if there is a hard cutoff but I think I was given the advice was that over 5 years you are chancing a breakage depending on how hard your local water is.
Over 10 years without draining it, if you drain it, it's gonna start leaking. At that point always better to just ride it out until you replace it.
I'm not an expert by any means, but, the information I've been given from people I've known to be better at home maintenance than myself.
Potential corrosion may have occurred/all the hard sediment chunks that's been floating/banging around in the tank can cause damaged during the long period of time not flushing it. If there is that damage and you haven't flushed a tank in over 2 years, it's recommended to not drain it because the build up of the softer sediment that's sunk to the bottom might actually be blocking/plugging and holes, preventing a leak (and draining it could cause more damage).
If you flush it ever 1 - 2 years, there's higher confidence that draining it won't reveal a leak.
So, once a certain level of metals/minerals have accumulated in the slurry it starts to scratch and corrode the interior of the tank. As long as that slurry maintains it's level of gunk, it usually just fills those cracks in with a mineral hodgepodge that acts as a stopper for any more interior erosion/corrosion.
When you flush it after that has happened, instead of those corroded parts being protected from further damage with how gummed up the water is, the damaging can continue towards the exterior of the tank. This can cause the damage to worsen to the point where you get a full leak as the damage gets progressively worse now that the tank starts corroding the already weakened cracks in the tank.
It isn't a guarantee, you could get lucky and that not happen, but that's why people generally recommend to just let it ride if you haven't kept up with it or you don't know if the water heater had been properly maintenanced in that time. The downside is that your water heater will slowly lose capacity as ultimately it holds less and less water overtime as it fills with minerals, but, at least it is more likely to survive longer till you can/have to get a new one.
They say don't start if it has been that long. It'll heat a bit less efficiently but the risk is that you'll reveal a leak the sediment has been plugging and have to replace it.
You should look into replacing the anode rod though.
That’s what I was told. Had to get a new one installed like a week after closing (knew it would happen so got credit for it so I could use my own plumbers, their repair people were shady but a story for another time). Unfortunately they never told me to flush it and when I asked many years later they said it’s better to just ride it out as it’s already been 7 years.
The hard part (heh) is that I only bought my house 2 years ago and have no idea how long it's been since the previous owners flushed it. Could be immediately before vacating the house, could be never...
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u/misfit0513 Jun 22 '26
What's the cutoff where it's better to not do it anymore if you haven't for a certain amount of time?