When a Troubled Tankless Unit Leads to a Smart Home Discovery
We get a lot of calls about tankless water heaters — misfires, inconsistent hot water, pressure problems. But a recent consultation at a home right here in Westford turned into one of the more interesting conversations we've had in a while. The homeowner had done serious diagnostic homework before we ever arrived, and along the way he'd installed something that stopped us in our tracks: a whole-home water monitoring and leak detection system that was genuinely impressive.
The tankless unit itself — a Rinnai, about 13 years old — was nearing the end of its useful life and showing all the signs. But the smart home water detector setup this homeowner had rigged up? That's worth talking about for any homeowner in Westford, Chelmsford, or Groton who's serious about protecting their home.
The Tankless Trouble: A Homeowner Who Did His Homework
By the time we arrived, this homeowner had already gone through a methodical troubleshooting process that most plumbing technicians would respect. He'd replaced the flow sensor (the old one was corroded), cleaned the flame rods, and performed a full descaling flush — an hour-long vinegar soak with his own pump and vinegar setup. He'd also pulled out a manometer and measured manifold gas pressure under load, reading 12 to 13 inches of water column, which put it within spec.
That's a lot of legwork. And yet the unit was still misfiring randomly — not tied to temperature, not tied to a specific demand pattern. Just unpredictable flame-outs.
He'd also done the right things on the venting side: checked and cleared the exterior vents, even used a borescope to inspect the flue. (He mentioned the borescope almost in passing — this is a guy who came from a 1912 house in Melrose and has seen his share of mechanical problems.) The filter was a little dirty; he cleaned it. Still, the misfires continued.
His remaining theory — and it's a reasonable one — was that the issue was either in the venturi/air pressure side of the combustion system or in the control board itself. Those are the two components he wasn't comfortable touching on his own, which is exactly why he called us.
The Smart Home Water Detector Setup That Impressed Us
Here's where the visit took a turn we didn't expect. Mounted near the tankless unit was a small relay — a YoLink device — wired so that the homeowner could power-cycle the water heater remotely from his phone. Because the unit misfired most often when someone was already in the shower upstairs, his wife had been climbing on a milk crate to unplug and replug the unit. The YoLink relay solved that immediately.
But the YoLink system went further than just a remote-controlled outlet. The homeowner had leak detectors placed throughout the home, all connected to a central hub in a utility closet. These aren't Wi-Fi devices — they operate on a long-range radio frequency, work up to nearly half a mile from the hub, and run on very low power. He mentioned the individual leak sensors cost around $20 each. The system also included real-time power monitoring, so he could watch the wattage draw of the water heater live from his phone.
As a home water detector solution, this is genuinely smart water sensing done right — inexpensive, reliable, and not dependent on your home Wi-Fi staying up. We were taking notes.
What the Gas Pressure Investigation Revealed
One clue the homeowner had picked up came from a neighbor. This is a development where many of the homes are similar in age — built around 2013 — and fed by propane with Eastern Propane as the supplier. His neighbor mentioned that her second-stage outdoor regulators had already been replaced twice because they were freezing and delivering inconsistent pressure. Her symptoms? Low pressure, inconsistent pressure, and flame-outs. Sound familiar?
The homeowner hadn't been able to test the outdoor regulators himself — his Amazon manometer didn't have the right adapter for that connection, and he wisely didn't want to improvise on the propane side. That's a job for a licensed technician. But the pattern was there: the regulator issue was apparently common enough on that street that neighbors were swapping notes about it.
This is worth flagging for any homeowner in Westford or the surrounding area on propane: if you're seeing random flame-outs on a gas appliance and you've exhausted the usual suspects, your outdoor regulator — especially a second-stage — deserves a close look. Freezing regulators are a real and underappreciated cause of intermittent gas appliance problems in New England winters.
The Bigger Issue: This Unit Was Undersized for the Home
Here's the uncomfortable truth we had to share. The home has four and a half bathrooms. The Rinnai tankless unit — rated somewhere around 5.3 gallons per minute — was simply not sized for that load. A neighbor with a similar home confirmed it: they run two tankless units in tandem and have no hot water issues.
Add to that the fact that this is a 440-foot well, so incoming water temperature is cold, which reduces effective output further. The master bath is on the opposite side of the house with no recirculation pump, meaning the homeowner is clearing close to 10 gallons of cold water from the pipes before hot water arrives. There's no recirc loop on this system by design — the manifold layout runs direct to fixtures — so a traditional recirculation pump isn't an option. A point-of-use demand-type recirculation valve at the fixture might help at the sink, but it's not a complete solution.
At 13 years old and undersized, this unit is approaching the end of its service life regardless of the misfire diagnosis. We discussed the comparison between a replacement tankless system and a high-efficiency hybrid heat pump tank. We also looked at a Noritz single-unit replacement, which offers 11 gallons per minute at a 70-degree rise and comes with a 25-year warranty — a significant jump in capacity. If a dual-unit setup were chosen, the existing 3-inch venting could stay. A single unit would drop to 2-inch. Given the 2013 vent pipes are still in place, that's a relevant factor in the decision.
Key Takeaways
Systematic troubleshooting matters. This homeowner ruled out the flow sensor, flame rods, scale buildup, manifold gas pressure, venting, and filter before calling us. That kind of documentation helps a technician skip to what's actually unresolved.
Outdoor propane regulators can freeze. If you're on propane in Westford, Groton, or Chelmsford and seeing random flame-outs, get your second-stage regulator inspected — especially after cold snaps.
A home water detector system doesn't have to be expensive. The YoLink leak detection setup this homeowner installed — with water sensing at multiple points, real-time power monitoring, and remote control — cost a fraction of what most people spend on smart home gadgets. It uses a dedicated hub rather than Wi-Fi, making it more reliable.
Tankless water heaters are not one-size-fits-all. A four-and-a-half-bathroom home on a deep cold-water well needs significantly more capacity than a 5.3 GPM unit can provide.
Know your unit's age and warranty status. At 13 years old, this Rinnai was approaching the end of its 15-to-20-year expected service life. Major repair investments rarely make sense at that stage — especially when the unit is undersized to begin with.
When the manufacturer won't talk to you, call a certified tech. Rinnai's tech support lines are generally restricted to licensed professionals. For a homeowner doing their own diagnostics, that's a real wall. Having a Rinnai-experienced technician who can actually call into support is a meaningful advantage.
Frequently Asked Questions
Can I install a water leak detector myself?
Absolutely. Standalone water sensing devices like the YoLink system we saw on this visit are plug-and-play and require no plumbing modifications. You place the sensor on the floor near a water heater, under a sink, or next to a washing machine, pair it with the hub, and it alerts your phone if it detects moisture. No Wi-Fi required for YoLink — it uses its own radio frequency. These are genuinely useful home water detector tools that cost very little.
Why does my tankless water heater keep shutting off randomly?
Random flame-outs on a tankless unit can have several causes: a failing or dirty flow sensor, corroded flame rods, scale buildup on the heat exchanger, inadequate gas pressure (including a failing outdoor propane regulator), blocked or dirty venting, or a failing control board. Work through the mechanical causes first before assuming it's the board. If you've done all of that and the issue persists, the venturi assembly and board are the final suspects — and at that point, it's worth having a technician with manufacturer tech support access take a look.
How do I know if my tankless water heater is undersized?
If you regularly run out of hot water when two or more fixtures are in use simultaneously, your unit may be undersized. Key factors are the unit's GPM rating, the number of bathrooms in your home, and your incoming water temperature (cold well water reduces effective output). A four-or-more-bathroom home on a deep well in New England generally needs a higher-capacity unit or a dual-unit setup than most single tankless installations provide.
What is a second-stage propane regulator and why does it matter?
Your propane system typically has two stages of pressure regulation: a first-stage regulator at the tank, and a second-stage regulator closer to the house. The second-stage unit reduces pressure to the level your appliances need. In cold weather, these regulators can freeze — especially if they're older — causing pressure drops that lead to intermittent flame-outs in your water heater, furnace, or other gas appliances. If neighbors on propane are reporting similar issues, a regulator inspection is a logical step.
Is a hybrid heat pump water heater a good alternative to a tankless unit?
For many homes, yes. Hybrid heat pump water heaters are significantly more energy-efficient than traditional tank units, and they store hot water so they're not affected by simultaneous demand spikes the way a tankless unit can be. The trade-off is that they require adequate space and a certain minimum ambient temperature to operate efficiently. They're worth comparing seriously against a high-output tankless replacement, especially if your current unit is undersized.
Ready to Talk Through Your Water Heater Options?
Whether you're in Westford, Chelmsford, Groton, or anywhere in the Middlesex County area, if you've got a tankless unit acting up — or you want to talk through a smart home water monitoring setup before your next leak becomes a flooded utility room — give us a call. We're Jeneral Plumbing, a family-owned company that actually enjoys this kind of problem-solving conversation. Reach us at (978) 392-7789. We're happy to walk through the diagnostics with you, discuss replacement options honestly, and help you figure out what actually makes sense for your home — not just what's easiest to sell.
Written by Jeneral Plumbing.
This article was drafted with AI writing tools from Jeneral Plumbing job notes and source materials, then edited before publication. AI tools did not inspect the job or validate technical conclusions.
Last updated .