Open 24/7 · San Marcos, TX

Water Heater Repair in San Marcos, TX

Water heater repair in San Marcos is mostly a hard-water story. City water tests in the hard range, so sediment and scale are behind many noisy, slow or failing tanks. Many households here rent, which adds a second question about who authorizes the fix. Call any hour.

Emergency? Call now, 24/7(737) 717-0737

Check the tankLeak, noise, or no heat?
Cut power or gas if wetClose the cold supply on a leak.
Call with the labelBrand, age and fuel help the first answer.

What we help with

Pages related to water heater repair in San Marcos

A heater call often leads to one of these. They cover the next decision.

Water heater replacement

When the tank has failed.

Water heater replacement details →

Tankless water heater

A different build with a different scale problem.

Tankless water heater details →

Water filtration in San Marcos

Taste, grit and what a filter cannot do.

Water filtration in San Marcos details →

Emergency plumber in San Marcos

For a tank that is flooding the closet.

Emergency plumber in San Marcos details →

Start here

Signs your San Marcos water heater needs repair

Match what you see to the card. Each one leads to a section below.

Popping or rumbling when the heater runsHard water leaves sediment under the heating zone, and steam bubbles push through it.Popping Hot water runs out quicklyA lower dip tube, a failed element or a thick sediment layer shrinks usable hot water.Short supply Water at the base of the tankA leak from the tank body means replacement. A leak from a fitting may be repairable.Base leak The relief valve line is drippingScale on the valve seat or high pressure. Never cap the line.Valve drip No hot water at all in an electric unitA tripped breaker, a failed upper element or a bad thermostat.Cold water Pilot light keeps going out on a gas unitA weak thermocouple or a draft. If you smell gas, leave.Pilot out Rust-colored hot water onlyThe tank lining or anode rod is wearing out.Rusty hot water Hot water smells like sulfur or eggsBacteria reacting with a depleted anode rod. Often fixable.Odor

Why call us

Why call for water heater repair in San Marcos

A heater problem is rarely just a heater problem. Water, gas and electricity all meet in one corner.

A person answers any hourSomeone is on the phone at every hour of the week.
Same-day service is availableA leaking tank is handled the same day.
No formsDescribe the sound or leak and talk it through.
Water, gas and power in one visitHeaters touch three systems, and one call covers them.
Honest repair or replace adviceYou hear when a repair is not worth it.

We vs others

What the call offers compared with waiting for a property manager

A work order is fine for a pilot light. A tank at the base needs speed.

	UsOnion Creek Plumbing	vsMany other plumbing companies
Hours	Open 24/7Cold showers at 6 a.m. are covered.	Business hours
Reaching someone	A person answersTalk through symptoms.	A ticket and a wait
How soon	Same-day service is availableLeaks go first.	Next available vendor
Jobs handled	Electric, gas, tank and tanklessOne call for any heater.	Only certain brands
Local knowledge	San Marcos water is hardSo scale is checked first.	Generic fault trees
Price clarity	Ask about pricing when you callRental cost responsibility follows the lease.	Estimate on arrival

Based on what is typical. Individual companies vary.

How it works

How water heater repair in San Marcos goes

The visit follows a simple order from safety to cause to fix.

Safety first
Leaks, gas smell, scalding water and wet wiring get attention before anything else.
Find the cause
The plumber checks power or gas, thermostat, elements, relief valve and tank condition.
Repair or advise
A fitting or element can be swapped. A failed tank gets a replacement plan.
Aftercare
You are told when to flush the tank and what to watch.

Pricing

What changes the price of water heater repair in San Marcos

Heaters are not all alike, and these things move the cost.

Electric or gas

Elements and thermostats differ from burners and gas valves. Ask about pricing when you call.

Which part failed

A thermostat is a small repair. A tank is not repairable.

Where the heater sits

Closets, attics and garages vary in access.

Scale on the parts

Heavy crust slows every step, from the drain valve to the elements.

Age and condition

An old tank may not be worth a repair.

Have this ready for the call

Fuel type: gas or electric
The label: brand, size, age if shown
What you hear, see or smell
Whether you rent and the owner’s contact

Ask about pricing when you call.

Call now, 24/7(737) 717-0737

Hard water at work

What hard water does inside a water heater in San Marcos

Minerals settle where it is hottest

A utility-reported figure for the City of San Marcos system was about 11.5 grains per gallon in 2025, with values up to roughly 15 reported. Heating makes dissolved calcium and magnesium drop out of the water. The solids sink to the bottom of a tank, or coat an electric element. The layer insulates the water from the heat, so the heater works harder and runs longer.

The signs are predictable: popping, a short supply, a drain valve that clogs, and early element failure. Flushing the tank slows the process, and softening the water slows it further. Systems on other suppliers, such as Crystal Clear SUD, may see less scale, so check your bill. The water heater noise guide explains each sound.

Inside a tank heater

Scale gathers at the bottom and around the elements; the drain valve and anode rod sit where it matters.

Fault finding

Symptoms, causes and fixes for water heater repair in San Marcos

A quick guide. The plumber confirms on site.
Symptom	Gas unit	Electric unit	Repair or replace
No hot water	Pilot out, bad thermocouple, gas valve	Tripped breaker, upper element, thermostat	Usually repair
Lukewarm	Dirty burner, low gas setting	Lower element failed	Usually repair
Popping noise	Sediment layer	Sediment on elements	Flush, then watch
Rotten egg smell	Anode rod reaction	Anode rod reaction	Usually repair
Water at tank base	Tank wall failure	Tank wall failure	Replace
Relief valve drip	Scale on seat or high pressure	Scale on seat or high pressure	Repair

Rotten egg smell in hot water only, not cold, usually points to the heater. A smell from both taps points elsewhere. For help deciding, read water heater repair vs replacement, and the core water heater repair page covers the general process.

Where is the water from

A leaking heater: tank wall, fitting or relief line

Three leaks, three answers

A tank wall leak is permanent. Water finds the weak point in the lining, and no patch fixes it. A fitting leak at the supply connections or the drain valve is a small repair. A drip at the relief line is a different issue: the valve is doing its job or its seat is dirty with scale.

Look closely before you decide. Wipe the tank dry and watch where it first shows wet. If the wetness starts at the top, it is probably a fitting. If it creeps from the bottom, expect to replace the tank. See water heater replacement for what that involves. Do not cap the relief line; that valve prevents overpressure.

Tracing a leak

Dry the surface
Wipe the tank and pipes with a rag.
Watch where water returns
The first wet spot shows the source.
Close the cold supply
Above the heater, to stop the refill.
Call and describe it
Top, side or bottom; the answer shapes the plan.

A few minutes of looking saves guesses.

In a rental

Reporting a heater problem when you rent in San Marcos

It is usually the owner’s equipment

Most San Marcos households, about 69 percent, do not own their home. The heater is normally part of the property, so repairs are usually the owner’s job under the lease. Practical steps help the repair go faster. Photograph the problem, send the owner or manager a written message that day, and note the date. A cold shower is an inconvenience, but a leak or a gas smell is an emergency and should be reported by phone too.

If the owner asks a plumber to call, the plumber needs access and a contact for approval. Being clear about that on the phone saves a second trip. The emergency plumber in San Marcos page covers urgent cases.

Who does what

The lease sets responsibilities.
Situation	Tenant move	Owner move
No hot water	Report in writing	Arrange repair
Slow leak	Close supply if safe, report	Arrange repair
Flooding closet	Shut supply, call plumber line	Arrange drying and repair
Gas smell	Leave, call from outside	Arrange safety check
Noisy tank	Report, keep a log	Plan a flush

Tenant and owner

Between repairs

A simple care routine for heaters in hard water

Small tasks that stretch a tank’s life

Flushing is the main job. Attach a hose to the drain valve, run it outside, open the valve and let water run until it clears. Do it with the power off or gas control set to pilot and the cold supply closed or open depending on the model’s manual. In hard water, many households flush yearly; heavy scale may need twice a year. If the drain valve clogs with grit, stop and call, because forcing it can break the valve.

Lowering the thermostat setting reduces scale growth and the risk of scalding. The anode rod is the sacrificial part that protects the lining. Checking it every few years can add life to the tank. For other jobs, see faucet repair when scale clogs aerators and water softener installation for scale control on the whole house.

Routine

Flush the tankOnce a year in hard water.
Test the relief valveLift the lever briefly each year.
Check the anode rodEvery few years.
Lower the settingHot enough, not scalding.
Look for rust at fittingsEarly sign of a slow leak.

Plan it in a calendar.

Repair or replace

When a San Marcos heater is past repair

Age matters, but condition matters more.
Clue	Points to
Water at the bottom of the tank	Replace
Tank is much older than usual and failing again	Replace
One failed element or thermostat	Repair
Relief valve drip	Repair
Pilot or ignition fault	Repair
Repeated failures after flushing	Check scale and age

A tankless model avoids a stored layer of sediment but still scales inside its heat exchanger in hard water. The tankless water heater page explains the trade-offs, and the tankless vs tank guide compares them. For taste and grit at the tap, see water filtration in San Marcos.

Questions

Questions about water heater repair in San Marcos

How quickly can water heater repair in San Marcos happen?

Same-day service is available. Leaks and gas smells go first, with other heater work fitted in around them, at any hour.

What does water heater repair in San Marcos usually cost?

The fuel type, the failed part, the location of the heater, the scale on the parts and the age of the unit decide it. A tank cannot be repaired when it leaks. Ask about pricing when you call.

How do I know if I can afford a repair or need a new unit?

Ask about pricing when you call, and ask what would change the answer once the tank is checked. A failed tank wall means replacement, while a thermostat or element is a small repair.

Why is my heater so noisy?

Sediment under the heating zone traps water, which flashes to steam and pops. San Marcos city water is hard, so this is common. A flush helps. Persistent noise may mean heavy scale.

Is hard water bad for a water heater?

It shortens life. Minerals form a layer that wastes energy and overheats the tank bottom or elements. Flushing and softening both help.

My heater is leaking. What should I do?

Close the cold supply above it, switch off power at the breaker or set the gas control to off, and call. Keep clear of wet wiring.

Should I turn my thermostat down?

Lower is usually better for scale and safety. Many households keep it in the middle range. Test water at a tap before you let children use it.

Can I flush the tank myself?

Many people do, with a hose and the manual. If the drain valve clogs or leaks, stop and call. Forcing it can break the valve.

Who pays for a heater repair in a rental?

The lease decides, but equipment that came with the property is usually the owner’s responsibility. Report the problem in writing and keep dated photos.

Is a rotten egg smell dangerous?

Hot-water-only sulfur smell is usually a harmless reaction between bacteria and the anode rod, but it is unpleasant. A smell of natural gas near the heater is different. Leave and call from outside.

What does a relief valve do?

It opens to release pressure or heat if the tank goes beyond safe limits. A drip means it is leaking or reacting to pressure. Never cap it.

Do you repair tankless heaters?

Yes. Tankless units scale up inside their heat exchanger in hard water and may need descaling. Tell the person what error code or symptom you see.

Guides

Guides for water heater problems

Heater trouble in San Marcos?

Tell us the fuel type and what the tank is doing. Water heater repair in San Marcos can be set up overnight too, and same-day service is available.