Most people who call about a rotten egg smell in their hot water have already poured something down the drain. It is the reasonable guess, except the smell comes back within a day, only shows up when the tap is running, and is worst in the shower, which is not how a drain behaves. In the homes between Buffalo Park and Seattle Hill Rd in Mill Creek, WA 98012, this complaint almost always traces back to the water heater, and it is one of the more common reasons we get asked about water heater repair in Mill Creek after a vacation.
Why this happens in Mill Creek north homes
Inside almost every tank water heater there is a long metal rod hanging into the water, usually magnesium. It is a sacrificial anode, and the name is the whole explanation: it corrodes so the tank does not. As the magnesium breaks down it sheds electrons into the water, and sulfate-reducing bacteria, harmless in themselves and present in plenty of supplies, take them and give off hydrogen sulfide. That is the egg smell. The rod has not failed. It is doing exactly what it was installed to do, in water that happens to have the wrong company in it.
It is the hot tap and not the cold because a tank is warm, dark and low on oxygen, and those bacteria like all three. Your cold lines are none of that and have no rod in them. It is also why tankless water heaters rarely produce it: no tank, no rod, nothing standing still.
Mill Creek is on municipal supply, so the smell here is rarely in the incoming water. Two local patterns account for most of the calls we take around 44th Ave SE:
- Water that stopped moving. A week away in August, a rental between tenants, a mother-in-law suite that sits empty half the year. The tank stays warm and still and the bacteria get an uninterrupted run at it. We take a lot of these calls the Monday after people get home.
- A new tank. Many of the 1990s and 2000s houses on the north end are on their second or third water heater, and a fresh magnesium rod is far more reactive than the worn stub it replaced. If your water carries the bacteria, the new heater produces more smell than the old one did. The tank is fine. It is the wrong rod for your water.
If a previous owner left a water softener in the garage, put it on the list too; they are a classic contributor. Whatever the trigger, the fix is some combination of flushing, sanitising and changing the rod, which falls under water heater repair in Everett and the surrounding cities rather than a replacement.
What to check first
- Rule out gas. Water heater sulfur arrives when a tap runs, from the water. Natural gas odorant is in the air, needs no tap running, and is strongest near an appliance or a gas line. If you smell rotten eggs in the air with no water running, treat it as gas: get everyone out of the house, then call from outside. That is a job for the emergency plumbing team, not a water heater conversation.
- Do the glass test. Fill a glass from a cold tap and carry it into another room, away from the sink and drain, before you smell it. Do the same with hot. Ninety seconds settles most of it.
- Hot tap only means the problem is inside the water heater. That is the outcome by a wide margin.
- Hot and cold both means the tank is off the hook and something upstream is carrying the odour in: the supply, an overdue filter cartridge, or an unserviced softener.
- One fixture only is usually a gunked-up aerator or a branch line to a bathroom used twice a year. Run that tap hard for a few minutes and see whether it clears.
- Flush the tank. Drain water off the bottom until it runs clean. Sediment is where the bacteria hide, and skipping this makes everything after it less effective.
If the flush did not hold, or you would rather not spend a Saturday draining a water heater into the driveway, call (425) 374-1557 or book a visit. We confirm where the smell is coming from before touching anything.
When it is past DIY
Start cheap and escalate only as far as you need to. After the flush, the next steps are where most homeowners should hand off:
- Sanitising. A peroxide treatment run through the tank and flushed back out knocks the population down. Putting chemicals into your own potable water is easy to get wrong, so this is where we would stop the DIY.
- The temperature treatment. State health guidance on sulfur bacteria calls for raising the tank thermostat to 160°F for about eight hours, since the bacteria die off above 140°F, then flushing. It is the fastest fix on the list, but it raises scald risk at every tap in the house, matters a great deal with kids or older adults and no mixing valve, and is not a setting to leave changed. Confirm the pressure relief valve works before anyone tries it.
- Changing the anode. This is the fix that sticks. An aluminium-zinc rod instead of magnesium usually ends it. A powered anode, which protects the tank electrically and sacrifices no metal, ends it more permanently for more money up front.
- A seized rod. Common on older tanks and anything crammed into a closet with no clearance above it. Rounding off a stuck anode makes the job worse. A plumber in Mill Creek who does these weekly will tell you up front whether the tank is old enough that a new rod is not the right money.
- Smell on the cold side of a private well. Some of the unincorporated lots out past 132nd St SE and Seattle Hill Rd are on wells, and groundwater is where sulfur usually originates. That deserves a proper water test before anyone replaces parts.
On the two questions everyone asks: you can shower in it in the ordinary case, since at the concentrations that come out of a home water heater this is an odour problem rather than a hazard, and if anyone in the house is genuinely reacting to it, get the water tested. And do not drink from the hot tap regardless, smell or no smell. Use the cold side. Water heater repair for Seattle Hill homes with this complaint is routine work, and our plumbing services page covers what else we can look at while the tank is drained.
Hot water smells like rotten eggs: Mill Creek questions
Why is it worse after we have been away for a week?
Because the water stopped moving. Fresh water coming in keeps a tank stirred and diluted; a still tank at a comfortable temperature is close to ideal for the bacteria involved. Set the heater to vacation mode before you go, and run the hot taps hard for a few minutes when you get back.
It started right after we got a new water heater. Is it defective?
No. A new tank comes with a fresh magnesium anode, far more reactive than the worn stub in the old unit. If your water carries the bacteria, the new rod produces more hydrogen sulfide than the old one did. The tank is fine. It is the wrong rod for your water, and the swap is straightforward.
Will a filter or a softener take care of it?
Not if the smell is forming in the tank, which is the usual case in Mill Creek. Filtration ahead of the heater cannot touch a reaction happening downstream of it. Treatment gear is the right answer when the odour is in the incoming water, mostly a well situation, and it should be specified from an actual water test.
Danika Plumbing & Electric, 11015 Airport Rd, Everett, WA 98204. We handle Mill Creek water heater repair from the shop at Paine Field and cover Seattle Hill, Silver Firs and Silver Lake on the same routes. Call (425) 374-1557 or schedule a visit and we will pull the rod, flush the tank and tell you straight whether it is worth keeping.
