Tankless Water Heaters - Plumbing Talks Forum

Tankless heater won’t always fire at the sink

andrewsnorkeler — Wed, 28 Oct 2026 01:50:56 +0000

What observations help distinguish a sink draw that’s below a tankless heater’s activation flow from an ignition, sensor, or gas-supply fault? Does the heater show an error code when it fails to start? I’d also want to know whether it fires reliably at a shower or another higher-flow tap, and whether the problem is limited to one fixture or happens at several. If it’s happening at multiple fixtures, or the heater reports a fault, would that point toward having a qualified technician diagnose it rather than changing the fixture flow?

What changes with a condensing tankless vent route?

etrekker14 — Mon, 26 Oct 2026 13:23:58 +0000

How much does choosing a condensing gas tankless heater change the installation when the route for venting is already constrained? I understand the exhaust is cooler than with a non-condensing model, but I’m unsure what that means in practice for approved vent materials and routing. The condensate side seems like another important difference: does a condensing unit generally need a drain and a neutralizer, and what upkeep do those add? If a suitable drain isn’t conveniently accessible, how much can that complicate the installation? I’m also curious whether the potential efficiency gain usually justifies those added requirements, or whether the answer depends too much on the specific model and layout.

Heat-pump tank recovery versus tankless gas demand

astronomy_nick — Sat, 24 Oct 2026 21:59:45 +0000

A heat-pump water heater can use less energy to heat water, but its stored supply has to recover after a busy stretch. A tankless gas heater avoids a storage tank, yet its performance depends on whether it can keep up with simultaneous draws and the temperature rise needed. How do homeowners compare the two fairly? Household peak hot-water demand and incoming-water temperature seem central to sizing, while a heat-pump unit also needs suitable space and airflow. I’m curious how much those installation constraints change the practical choice, and how tank standby losses compare with gas use when a tankless unit serves intermittent demand.

Hard water and tankless descaling: when does a softener make sense?

Steadymaker5360 — Fri, 23 Oct 2026 06:58:46 +0000

How do you decide whether periodic descaling is enough for a tankless heater, or whether treating hard incoming water with a softener is worth the added upkeep? I’d want to base that on an actual hardness test and the heater manufacturer’s guidance, rather than assume every tankless unit needs a softener. The two maintenance burdens seem different: descaling is heater-specific, while a softener needs its own ongoing attention. For people who’ve compared the approaches, what hardness level or manufacturer recommendation tipped the decision? And how much did drain access and local plumbing requirements affect whether a softener was practical to install?

Recirculation can outpace a tankless heater’s minimum flow

dieselinferno32 — Wed, 21 Oct 2026 01:52:18 +0000

Recirculation can shorten the wait for hot water, but I’m curious how well it works with a tankless heater that needs a minimum flow to fire. Could a pump’s flow or control strategy cause frequent starts and stops, or does the heater’s recirculation mode manage that differently? A dedicated return line seems like a different setup from a crossover valve that sends cooled hot-water-line water back through the cold pipe. What should the heater manual or installer confirm about the approved piping arrangement, pump control, and operating mode before choosing between them?

How often should a tankless inlet screen be cleaned?

Friendlyplanner8497 — Mon, 19 Oct 2026 10:25:28 +0000

Is the cold-water inlet screen on a tankless heater usually cleaned on a set schedule, or does the manual tie it to water conditions or signs of restriction? I’d rather not remove it unnecessarily, but I’m also unsure what symptoms point to a clogged screen rather than scale inside the heater or a restriction elsewhere in the water supply. For those who’ve checked their model’s manual, what interval does it specify? And before removing the screen, what shutoff and pressure-relief steps does the manufacturer call for? I know the procedure can vary by model, so I’m interested in how to find the right instructions without risking a leak or interrupting service unexpectedly.

Brief temperature swings during a low-flow draw

Clearplanner6135 — Wed, 07 Oct 2026 16:52:30 +0000

Can short temperature swings at one fixture happen because a tankless heater is operating near its minimum firing rate, or would you suspect something at the fixture first? I’d expect the pattern to matter: does it happen only when the flow is turned down, and only at one faucet or shower, or does it show up at several fixtures too? If the heater’s display shows flow rate or the burner cycling, are those readings useful for telling normal low-demand behavior from a fixture-side restriction or control problem?

Tankless water heaters: casing leaks versus connection leaks

william_whiskers — Fri, 17 Apr 2026 05:53:15 +0000

For a tankless water heater, how do you compare water coming from inside the casing with a leak at an external pipe connection? By ‘box’ here I mean the heater itself. A washing-machine outlet box or an under-sink fitting is a different component, even if the visible drip looks similar.

What information helps a service technician work out the source and likely repair scope before parts are replaced? I’m interested in the distinction, rather than assuming every internal drip is a failed heat exchanger or every connection leak is a quick tighten-up.

my tankless heater acting weird again, help?

gandalfrunner — Mon, 07 Apr 2025 13:41:41 +0000

So I just learned the other day that sometimes tankless water heaters shut down randomly because of scale build-up inside... who knew? I guess minerals from hard water can mess things up. Anyway, anyone dealt with this sorta thing before?

Quick trick to keep your tankless running smooth

cosplayer58 — Sun, 06 Apr 2025 20:56:18 +0000

Just wanted to share something I learned the hard way. If you've got a tankless water heater, you really gotta flush it out once a year or so. I ignored mine for like three years (oops), and the buildup was pretty nasty. Anyway, vinegar works wonders - just pump it through for about an hour and you're good. Curious if anyone else has their own little tricks or shortcuts for keeping these things clean?