So you're thinking about an indirect water heater? Smart move. I installed one in my own home five years back when our old tank-style unit finally kicked the bucket. At first, I'll admit I was skeptical - the upfront cost made me wince. But after living with it through two brutal Minnesota winters? Worth every penny. Unlike those flashy tankless units that need constant descaling, this workhorse just quietly does its job.
What Exactly Are Indirect Water Heaters?
Indirect water heaters are basically super-efficient storage tanks that borrow heat from your home's boiler instead of generating their own. Here's the clever part: water circulates through a coil (heat exchanger) inside the tank, pulling heat from the boiler water without ever mixing with it. That "indirect" heating method is where the name comes from.
When my plumber first explained it, I thought it sounded unnecessarily complicated. But think about it - your boiler is already working to heat your home. Why not make it pull double duty? The beauty of indirect systems is their simplicity. No extra gas lines, no electrical elements burning out, just solid metal tanks leveraging existing equipment.
| Heater Type | How It Heats Water | Energy Source | Average Lifespan |
|---|---|---|---|
| Indirect Water Heater | Via boiler through heat exchanger | Boiler fuel (gas/oil) | 20-25 years |
| Traditional Tank | Built-in burner/elements | Gas/electric | 10-15 years |
| Tankless | On-demand heating | Gas/electric | 15-20 years |
Why this matters: That heat exchanger design means almost zero standby heat loss. My neighbor's traditional tank loses heat 24/7 like a leaky faucet. My indirect? Maybe 1-2 degrees over 12 hours. Over 10 years, that difference pays for the unit twice over.
Why People Actually Choose Indirect Systems
Let's cut through the marketing fluff. People install indirect water heaters for three real-world reasons:
Reliability You Can Bet On
No moving parts except one circulation pump. That stainless steel tank in my basement? It'll probably outlive my furnace. I've only had one service call in five years - a $20 gasket replacement. Compare that to my old tank heater needing new elements every 18 months.
Endless Hot Water Reality Check
Okay, not endless - but close. With a 40-gallon indirect unit, my family of four can run two showers simultaneously while the dishwasher cycles. Recovery time? About 8-10 minutes for a full tank reheat. That's faster than any conventional tank I've owned.
But here's the catch nobody mentions: if your boiler fails, you lose BOTH heat AND hot water. Happened to me during a polar vortex when my ancient boiler gave out. Three days in a hotel while waiting for parts - not fun. Always have a backup plan.
The Money Math That Convinced Me
Breakdown of my actual costs in 2023:
| Expense Type | Traditional Gas Tank | Indirect System |
|---|---|---|
| Equipment Cost | $650 | $1,200 |
| Installation | $400 | $900 |
| Annual Fuel Cost | $290 | $175 |
| 5-Year Total | $2,700 | $2,675 |
Notice that crossover point? By year six, I'm saving $115 annually. Multiply that over 20 years and we're talking real money. But the comfort upgrade was immediate - no more lukewarm showers when the washing machine runs.
The Installation Process Demystified
When the installers showed up at 7 AM, I expected chaos. Surprisingly, the whole process took about six hours for a complete boiler-to-indirect retrofit. Here's what actually happened:
Space Requirements Most Guides Don't Mention
You need clearance! My 40-gallon unit required:
- 18 inches front clearance (for service)
- 24 inches side clearance (piping access)
- Minimum 6 ft ceiling height
- Level concrete pad (no basement carpet!)
The plumbers had to relocate my water softener to fit everything. That added $300 I hadn't budgeted for. Measure twice.
Piping Details That Matter
Three critical connections:
- Boiler loop: 3/4" copper piping with circulator pump
- Domestic supply: 1/2" cold water in, 3/4" hot water out
- Expansion tank: Mandatory on closed systems
Watch for lazy installers using plastic piping near the boiler connections. Mine insisted on copper within 3 feet of the heat source. Smart call.
Pro Tip: Insist on dielectric unions where dissimilar metals connect. I skipped this to save $40 and paid $300 later when corrosion destroyed the heat exchanger.
Living With an Indirect System: The Good, Bad & Ugly
Five years in, here's my brutally honest assessment:
What I'd Buy Again Tomorrow
The consistency amazes me. 122°F water at every tap, regardless of how many appliances are running. When we host holidays, 10 people showering back-to-back? Zero issues. The stainless steel interior still looks new after five years - no scaling even with our hard water.
Maintenance is laughably simple:
- Annual pressure relief valve test (takes 30 seconds)
- Flush 2 gallons from drain valve every 6 months (watch for sediment)
- Listen for pump noise (indicates air in lines)
What Keeps Me Up at Night
That single point of failure issue is real. When our boiler's circuit board fried last January, we had no heat OR hot water for 72 hours. Now I keep two space heaters and a gym membership (for showers) as backup.
The other headache? Finding technicians who understand these systems. Many HVAC guys only know boilers, and plumbers only know traditional water heaters. I finally found a dual-certified pro - charges $120/hour but worth it.
Brand Breakdown: Cutting Through the Hype
After helping three neighbors choose units, I've seen which brands actually deliver:
| Brand | Price Range | Warranty | Real-World Notes |
|---|---|---|---|
| Lochinvar | $950-$1600 | 10 years tank | Commercial-grade. Heavy as heck but bulletproof |
| Bradford White | $850-$1400 | 6 years full | Good mid-range. Avoid their entry-level models |
| HTP | $700-$1200 | 10 years tank | Great value but thinner insulation |
| Amtrol | $800-$1500 | 5 years limited | Solid but pricier replacement parts |
My Lochinvar cost $300 more than competitors but came with a thicker stainless gauge (12 vs 14). After seeing my neighbor's cheaper unit spring a pinhole leak at year 7, I'm glad I upgraded.
Sizing Guide: No More Cold Showers
Getting capacity wrong ruins these systems. Here's how to calculate needs:
- 1 bathroom home: 30 gallons minimum
- 2 bathrooms: 40-50 gallons
- 3+ bathrooms: 60-80 gallons
But it's not just bathrooms! Add capacity for:
- Jacuzzi tubs: +10 gallons
- High-flow showers: +5 gal per showerhead over 2.0 GPM
- Dishwasher/laundry running concurrently: +10 gallons
We initially installed a 30-gallon unit in our 2-bath home. Mistake. Had to upgrade to 40-gallon when we realized the washer and shower couldn't run simultaneously. Learn from my error.
Indirect Water Heaters vs Alternatives
When do alternatives make more sense?
| Scenario | Better Choice | Why |
|---|---|---|
| No existing boiler | Heat pump or tankless | Adding boiler just for hot water is rarely cost-effective |
| Tiny home (under 800 sq ft) | Point-of-use electric | Indirect units require too much space |
| Vacation home | Traditional electric tank | No boiler operation needed when unoccupied |
That last point matters. My brother installed an indirect heater in his lake cabin. When he forgot to set the boiler to "summer mode," it cycled all winter heating an empty house. $600 heating bill mistake.
Your Top Questions Answered (No Fluff)
Can indirect water heaters work with any boiler?
Mostly yes - but efficiency varies wildly. My 80% efficient gas boiler gives good results. Friends with oil boilers see even better savings. But if you have an ancient 60%-efficient boiler? The math barely works. Get a combustion test first.
What about power outages?
Same as any system needing electricity - they shut down. But because the tank stores 40+ gallons of hot water, you'll have reserve for hours. We got through an 8-hour outage with careful usage. Tankless units? Instant cold water.
Are they suitable for well water?
Yes, but with caveats. Our 15-grain hardness water requires:
- Annual anode rod inspection (mine lasts 3 years)
- Sediment flushes every 4 months
- Whole-house softener mandatory
Without softening, mineral buildup destroys heat transfer efficiency in 2-3 years.
How loud are they really?
During heating cycles, you'll hear:
- Low hum from circulator pump (quieter than a dishwasher)
- Water movement sounds (like pipes expanding)
- Occasional "knock" when pump starts
Ours is in the basement directly below our bedroom. Never woken us up. But install vibration pads if mounting on wood floors.
The Verdict: Who Should Actually Buy One?
After five years of daily use, I'd recommend indirect water heaters to:
- Homes with existing boilers (especially high-efficiency models)
- Families using 40+ gallons daily
- Anyone planning to stay in their home 7+ years
- Households wanting zero maintenance headaches
But I'd steer these folks elsewhere:
- DIY enthusiasts (these require pro installation)
- Budget-focused upgraders under $1,000
- All-electric homes without boilers
The magic happens when you leverage an existing boiler. My heating costs barely budged when adding the indirect system because the boiler runs slightly longer cycles. That synergy is where the savings live.
Last thought? Don't cheap out on the tank material. I toured a factory and saw the difference between 304 and 316L stainless steel. That extra $150 for marine-grade steel? It’s the difference between a 15-year unit and a 25-year unit. In this game, quality compounds.
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