When a water heater rumbles, pops, or ticks, most homeowners look at the softener first because it is the big piece of equipment on the same line. That instinct is understandable, but it often points the wrong way. A softener reduces the hardness minerals in the water it treats. It does not clean out a water heater that already holds a layer of sediment, and it does not remove every particle that might reach the tank. Before you call anyone about the softener, sort out where the noise and the symptoms are coming from.
What the noise usually means
In a storage water heater, a rumble or pop often comes from water boiling in pockets beneath a layer of sediment at the bottom of the tank. As the burner or element heats the tank, trapped water flashes to steam and cracks through the deposit. Over time that layer can also insulate the bottom of the tank, so the heater runs longer to reach the same temperature. A popping sound on its own does not prove a failure, but it is a reason to look at the tank and the water feeding it.
Pay attention to when the sound happens. If it appears only while the heater is running, the heater is the first suspect. If it seems to follow water use, such as during a long shower or right after a load of laundry, check whether the noise is coming from the pipes or the fixtures instead.
Check which line is affected
Run the cold tap at the kitchen sink for a minute, then run the hot tap. Look for grit, cloudiness, or a brownish tint in each. The pattern tells you a lot.
If only the hot line shows grit or the hot water is running weaker or swinging in temperature, the heater tank is the more likely source. If both the hot and cold lines carry the same grit, the problem is upstream of the heater, and the softener, the supply line, or the municipal main becomes a fair thing to investigate. If the grit shows up in the cold line only after the softener has gone through a regeneration cycle, that is a reason to call the softener service provider and describe exactly when the grit appears.
What you can check yourself
Read the heater's owner manual before you touch anything. Most manuals describe a periodic flush of the tank through a drain valve near the bottom. Flushing can help with sediment, but it is not safe to open a hot tank without following the manufacturer's steps, including turning off the power or gas supply and letting the water cool first.
Write down the date-free details you can observe: how often the noise happens, whether hot water runs out sooner than it used to, whether the temperature changes during a shower, and whether the noise matches the cycle of the heater. Those notes help a technician narrow the problem faster and keep you from paying for work that does not address the cause.
What to ask a technician
Ask whether the heater itself has been inspected for sediment buildup and whether the tank drain has been tested for flow. Ask how the technician separates a heater problem from a water quality problem, and what they would expect to see in the cold line if the softener were the cause. A clear answer to that question is more useful than a general statement that the water is hard.
A water heater that pops is worth taking seriously, but the first job is to find out which part of the system is making the sound. Sorting the heater from the softener at the start saves time, and it keeps the repair focused on the component that actually needs attention.