Water Heater Problems on a Home Inspection Report
Water heater notes are common on inspection reports. Age and a missing relief-valve pipe are the common ones and usually cheap or just budget items. Backdrafting on a gas unit is the one to treat as a safety issue.
I'm Wes Johnston, a Realtor with Trueblood Real Estate in Fishers. Before real estate I earned a construction engineering management degree from Purdue and spent about ten years designing custom homes and running their construction in Hamilton County. I'm not a home inspector, electrician, plumber or engineer, and this isn't a substitute for one. It's how I explain these findings to my own clients. Sources are linked as you go.
Short answer: most water heater findings are small plumbing corrections or a heads-up that the tank is getting old. A gas water heater that backdrafts exhaust into the house is a carbon monoxide hazard and needs a plumber or HVAC contractor before closing. Ask for repairs by a licensed plumber, or take a credit if the tank is old enough that you'd replace it anyway.
- Typical cost to fix
- Replacement about $882 to $1,826 (average $1,348); tankless about $1,406 to $3,902. An expansion tank is $90 to $350 plus labor.
- Who to call
- A licensed plumber. For gas venting and backdrafting, a plumber or HVAC contractor.
- Deal-breaker?
- No. Even a full replacement is one of the smaller big-ticket items on a report.
Cost source: HomeAdvisor water heater cost guide and tankless cost guide, both updated June 17, 2026. National figures.
- 01What do water heater notes on a home inspection report mean?
- 02How do I tell how old a water heater is?
- 03What is a TPR valve and why does the discharge pipe matter?
- 04Do I need an expansion tank on my water heater?
- 05What does backdrafting on a gas water heater mean?
- 06Is sediment or a rumbling water heater a problem?
- 07How much does it cost to replace a water heater, tank vs. tankless?
- 08Should I ask the seller to fix or replace the water heater?
- 09I'm selling. Should I fix the water heater first?
What do water heater notes on a home inspection report mean?
The inspector checks that the water heater makes hot water, reads the data plate, and looks at the safety parts around it: the temperature and pressure relief (TPR) valve and its pipe, the gas venting, the gas shutoff, the drain pan, and whether there's an expansion tank. Typical report wording:
- "Water heater is near or beyond the end of its typical service life." A budget item.
- "TPR valve discharge pipe missing" or "discharge pipe improperly terminated." A cheap fix that matters.
- "No thermal expansion tank observed." Depends on your plumbing; see below.
- "Backdrafting observed at draft hood" or "vent connector improperly sloped." The safety item.
- "Rust/corrosion at fittings," "evidence of leaking," or "water in drain pan." Watch closely; a leaking tank is near the end.
- "Rumbling noise," or "sediment." Maintenance.
How do I tell how old a water heater is?
Read the serial number on the data plate. Most manufacturers code the build date into it. A few examples from InterNACHI's dating chart (InterNACHI water heater dating chart):
| Brand | How to read it | Example |
|---|---|---|
| Rheem / Ruud | First four digits: month, then year | 0189… = January 1989 |
| A.O. Smith | 2nd character is the month letter (A = January to M = December), 3rd and 4th are the year | AJ89… = October 1989 |
| Bradford White | 1st letter is the year (repeats every 20 years), 2nd letter is the month | JM… = December 1992 or 2012 |
| American / Whirlpool | First two digits are the year, next two are the week | 8906… = 6th week of 1989 |
Then compare it to typical life. InterNACHI's chart lists a conventional tank water heater at 6 to 12 years and an on-demand (tankless) unit at about 10, as guidelines only (InterNACHI life expectancy chart, read October 2026). Manufacturers' ratings and warranties on tankless units are often longer, so check the unit's warranty. An older tank that's dry and working is a budget item. An older tank with rust at the base or water in the pan is telling you it's close.
What is a TPR valve and why does the discharge pipe matter?
The temperature and pressure relief valve is the brass valve near the top of the tank. If the water gets too hot or the pressure too high, it opens and dumps scalding water so the tank doesn't. The pipe attached to it decides where that water goes. Without a pipe, it sprays sideways at whoever is standing there.
The model plumbing codes are specific about that pipe. Per the ICC's summary of the 2021 International Plumbing Code and International Residential Code, it must be no smaller than the valve outlet, rated for at least 100 psi at 180°F, serve only that one valve, run downhill with no traps or sags, have no valves or tees in it, end in the same room through an air gap no more than 6 inches above the floor or a drain, be visible, and have no threads at the end (ICC CodeNotes, Water Heater Safety). Indiana adopts its own plumbing code, but these are the standards inspectors write to.
Common write-ups: no pipe at all, a pipe that's smaller than the valve, PVC that isn't rated for the heat, a pipe that ends a foot off the floor, or one that runs up and over something. Each is a small plumber fix, usually done in the same visit as anything else on the list.
Do I need an expansion tank on my water heater?
Water expands when it's heated. In an open system, that extra volume pushes back into the city main. Once the cold water passes through a check valve, a backflow preventer or a pressure reducing valve, it can't go back, so pressure climbs every time the heater runs and the TPR valve ends up doing the job.
The model plumbing code covers this. The 2018 International Plumbing Code (section 607.3) requires a thermal expansion control device on the cold supply when a storage water heater is fed through a check valve, pressure reducing valve or backflow preventer, installed downstream of those devices and sized to the manufacturer's instructions (Colorado Division of Housing memo quoting the IPC). Local rules and whether your meter has a check valve decide whether you need one, so ask the plumber.
Signs you need one: the TPR valve drips now and then, the pressure at a faucet spikes after the heater runs, or there's a pressure reducing valve on the main. HomeAdvisor puts an expansion tank at $90 to $350 plus labor (HomeAdvisor, updated June 2026).
What does backdrafting on a gas water heater mean?
A standard gas water heater sends its exhaust up the vent by natural draft. Backdrafting is when that exhaust comes back out at the draft hood into the room instead. InterNACHI describes the causes as low indoor air pressure from exhaust fans, dryers or fireplaces, or a blocked or badly configured flue, and names soot on top of the heater and spillage at the draft hood as signs (InterNACHI on backdrafting).
This is a carbon monoxide issue. The CPSC says more than 200 people a year die from unintentional, non-fire carbon monoxide poisoning, and it lists water heaters among the fuel-burning appliances to have professionally inspected every year (CPSC Carbon Monoxide Information Center, read October 2026).
Common causes on a resale house: the vent connector sloping the wrong way, a disconnected or rusted vent pipe, a heater that shares a chimney with a furnace that was replaced with a high-efficiency unit (now the old chimney is too big for the water heater alone), or a tight utility room. The fix ranges from reconnecting a pipe to relining the chimney. Have it diagnosed by a plumber or HVAC contractor before the inspection deadline, and make sure there's a working CO alarm.
On a new house, the water heater's venting is designed with the furnace's. If one gets swapped for a power-vent or high-efficiency model later, the other one's vent may not work right anymore. When I look at an older Indianapolis house with a new furnace and an old gas water heater on the same chimney, that's the first thing I'd ask the contractor to check.
I also tell buyers to look at the top of the water heater. Soot, rust or scorch marks around the draft hood are worth a photo for the plumber.
Is sediment or a rumbling water heater a problem?
It's maintenance, not a defect. Rheem says minerals settle at the bottom of a tank and cause popping and rumbling, act like insulation so the burner runs longer, and add wear. It recommends flushing once a year, or every six months with hard water (Rheem on flushing; Rheem on water heater noises).
One caution for buyers: Rheem also warns that older tanks that haven't been flushed in a long time can leak if you try, and recommends a professional for units around 8 to 12 years old or older (Rheem). On an older tank, a rumble is a reason to budget for replacement, not a reason to start opening valves.
How much does it cost to replace a water heater, tank vs. tankless?
National figures from HomeAdvisor, updated June 17, 2026:
| Type | Installed cost |
|---|---|
| Typical replacement (all types) | $882 to $1,826, average $1,348 |
| Gas tank | $700 to $2,700 |
| Electric tank | $600 to $3,500 |
| Tankless | $1,406 to $3,902, average $2,641 |
| Expansion tank | $90 to $350 plus labor |
Sources: HomeAdvisor water heater cost; HomeAdvisor tankless water heater cost. National figures; Indianapolis-area quotes vary.
Tankless costs more up front partly because switching often means a bigger gas line, new venting or a new electrical circuit. If you're replacing an old tank because of an inspection, a like-for-like tank is the quick, predictable fix. Going tankless is a decision to make after closing, with your own plumber.
Should I ask the seller to fix or replace the water heater?
Ask for the safety items to be fixed: a missing or wrong TPR discharge pipe, venting or backdrafting problems, a gas leak, or an active leak at the tank. Those are reasonable requests, and they should be done by a licensed plumber with a receipt. You can check an Indiana plumbing license with the state license lookup.
For an old tank that still works, I usually suggest a small credit or nothing, not a demand for a new one. If the tank is leaking or not making hot water, a credit based on a plumber's quote lets you choose the replacement. For how the response works, see how the inspection period works in Indiana.
If the report also has plumbing pipe or HVAC notes, bundle them into one plumber or contractor visit. See galvanized pipe findings and furnace and AC findings.
I'm selling. Should I fix the water heater first?
Fix the small things before you list. A proper TPR discharge pipe, a reconnected vent, a drain pan under a tank in a finished area: these are inexpensive and they come off the buyer's report. If the tank is old and you've had it serviced, keep the receipt.
Replacing an old but working tank isn't required and usually isn't worth doing just for the sale. If it's leaking, replace it or disclose it. More: what to fix before selling and the Indiana seller's disclosure.
Why a Realtor Who Built Houses Reads Reports Differently
A home inspection report runs dozens of pages, and almost every item ends with "recommend evaluation by a qualified professional." That wording is there for the inspector's protection. It doesn't tell you which items are a quick fix and which ones change the deal.
I spent about ten years designing houses and running their construction before I sold them. When my clients get their report, we go through it together and sort it into what to ask for, what to take as a credit, what to just fix yourself later, and what needs a specialist before the inspection deadline. If you're buying or selling in central Indiana, I'm happy to do the same for you.
Construction engineer turned Realtor. Straight answers before you sign.
Send Me the Page That Worries You
Tell me the address and the finding. I'll tell you how serious it looks from a builder's point of view and how it usually gets handled in a deal.
Send a MessageWhat's Your Home Worth?
Selling an older home? Start with a realistic price based on recent local sales.
Have a Water Heater Question?
Send the address and the line from the report. I'll get back to you with how serious it looks and how it usually gets handled.
General guidance from a Realtor with a construction background. Hire the licensed trade for the diagnosis and the fix.
General information from a Realtor with a construction background, not plumbing, legal or safety advice. Cost ranges are national figures from HomeAdvisor (updated June 2026); Indianapolis-area quotes vary. Code items are from the ICC's summaries of the model codes; Indiana adopts its own plumbing code. Have a licensed plumber evaluate and repair water heater findings.