{"id":1398,"date":"2026-05-15T08:43:04","date_gmt":"2026-05-15T13:43:04","guid":{"rendered":"https:\/\/plumbing101.i234.me\/wordpress\/?p=1398"},"modified":"2026-05-14T05:34:26","modified_gmt":"2026-05-14T10:34:26","slug":"tankless-heater-roaring-check-this-first","status":"publish","type":"post","link":"https:\/\/plumbing101.i234.me\/wordpress\/tankless-heater-roaring-check-this-first\/","title":{"rendered":"Tankless Heater Roaring? Check This First"},"content":{"rendered":"

A new tankless water heater should not cause immediate concern.<\/p>\n

But loud intake noise, high gas consumption, and fluctuating water temperature can occur after a poor setup.<\/p>\n

One homeowner had a new A. O. Smith 95% efficient tankless water heater installed.<\/p>\n

A licensed plumber did the work.<\/p>\n

Right after the install, problems started.<\/p>\n

When a vanity faucet or shower was turned on, the unit became loud.<\/p>\n

The intake sounded strong.<\/p>\n

The gas burner also seemed to run very hard.<\/p>\n

The owner compared it to pressing the gas pedal in a car.<\/p>\n

The water temperature also moved up and down.<\/p>\n

It jumped between about 100\u00b0F and 138\u00b0F.<\/p>\n

That is not normal comfort for a shower.<\/p>\n

It can also be unsafe.<\/p>\n

Question<\/h2>\n

Did the installer install the tankless water heater incorrectly, or is the heater defective?<\/p>\n

Answer<\/h2>\n

It could be either one, but the install should be checked first.<\/strong><\/p>\n

A tankless heater must have the right gas supply, venting, water flow, and setup.<\/p>\n

If any part is wrong, the unit may run loudly.<\/p>\n

It may also fail to hold a steady temperature.<\/p>\n

A bad gas valve is possible.<\/p>\n

A. O. Smith tech support may be right to suspect it.<\/p>\n

Still, a new unit should not be blamed before checking the installation.<\/p>\n

The plumber should confirm gas pipe size, gas pressure, vent length, vent slope, and clearances.<\/p>\n

The plumber should also check the water flow rate at each fixture.<\/p>\n

Low flow can make a tankless heater cycle poorly.<\/p>\n

Dirty faucet aerators can also cause flow problems.<\/p>\n

You can review A. O. Smith supports information at\u00a0Hotwater.com support<\/a>.<\/p>\n

You can also contact A. O. Smith technical support through their\u00a0official tech support page<\/a>.<\/p>\n

What About the 3-Inch Exhaust Vent?<\/h2>\n

The vent issue may be the bigger concern.<\/p>\n

A tankless exhaust vent must follow the manufacturer\u2019s manual.<\/p>\n

It must also meet local code.<\/p>\n

Moving the vent four feet up the exterior wall may be allowed.<\/p>\n

But it depends on clearances.<\/p>\n

The vent must stay away from windows, doors, air intakes, corners, and grade.<\/p>\n

It must also be kept away from the AC condenser.<\/p>\n

The AC unit needs clear air flow.<\/p>\n

Hot exhaust should not blow into it.<\/p>\n

That can hurt performance.<\/p>\n

It may also cause corrosion over time.<\/p>\n

Ask the plumber to show the exact vent clearance chart from the manual.<\/p>\n

Also, ask for the local inspector to review the final vent location.<\/p>\n

You can view general fuel gas code information through the\u00a0International Fuel Gas Code<\/a>.<\/p>\n

What Should the Homeowner Do?<\/h2>\n
    \n
  1. Stop guessing and document each problem.<\/li>\n
  2. Take photos of the vent, AC unit, and wall area.<\/li>\n
  3. Record the water temperature swings.<\/li>\n
  4. Ask the plumber for a written install checklist.<\/li>\n
  5. Call A. O. Smith with the model and serial number.<\/li>\n
  6. Ask the local inspector about the vent change.<\/li>\n<\/ol>\n

    Do not accept a vent move without code proof.<\/p>\n

    Also, do not accept loud operation as normal without testing.<\/p>\n

    A tankless water heater should be safe, steady, and properly vented.<\/p>\n

    I’m Chris Mayer, writing for Plumbing 101<\/a>.<\/p>\n

    \"Tankless
    Tankless Heater Roaring? Check This First<\/figcaption><\/figure>\n","protected":false},"excerpt":{"rendered":"

    A new tankless water heater should not cause immediate concern. But loud intake noise, high gas consumption, and fluctuating water temperature can occur after a poor setup. One homeowner had a new A. O. Smith 95% efficient tankless water heater installed. A licensed plumber did the work. Right after the install, problems started. When a… Continue reading Tankless Heater Roaring? Check This First<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":1500,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_wpscp_schedule_draft_date":"","_wpscp_schedule_republish_date":"","_wpscppro_advance_schedule":false,"_wpscppro_advance_schedule_date":"","_wpscppro_dont_share_socialmedia":null,"_wpscppro_custom_social_share_image":0,"_facebook_share_type":"default","_twitter_share_type":"default","_linkedin_share_type":"default","_pinterest_share_type":"default","_linkedin_share_type_page":"","_instagram_share_type":"default","_medium_share_type":"default","_threads_share_type":"default","_google_business_share_type":"default","_selected_social_profile":[],"_wpsp_enable_custom_social_template":false,"_wpsp_social_scheduling":{"enabled":false,"datetime":null,"platforms":[],"status":"template_only","dateOption":"today","timeOption":"now","customDays":"","customHours":"","customDate":"","customTime":"","schedulingType":"absolute"},"_wpsp_active_default_template":true},"categories":[79],"tags":[1091,725,557,1095,109,235,111,1097,1094,115,1145,1144,1093,1092,910,1096],"class_list":["post-1398","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-general-plumbing-help","tag-ao-smith-tankless-water-heater","tag-check","tag-first","tag-gas-valve-problem","tag-general","tag-heater","tag-help","tag-licensed-plumber","tag-loud-tankless-water-heater","tag-plumbing","tag-roaring","tag-tankless","tag-tankless-venting-code","tag-tankless-water-heater-temperature-swings","tag-this","tag-water-heater-exhaust-vent","entry"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/plumbing101.i234.me\/wordpress\/wp-json\/wp\/v2\/posts\/1398","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/plumbing101.i234.me\/wordpress\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/plumbing101.i234.me\/wordpress\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/plumbing101.i234.me\/wordpress\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/plumbing101.i234.me\/wordpress\/wp-json\/wp\/v2\/comments?post=1398"}],"version-history":[{"count":1,"href":"https:\/\/plumbing101.i234.me\/wordpress\/wp-json\/wp\/v2\/posts\/1398\/revisions"}],"predecessor-version":[{"id":1501,"href":"https:\/\/plumbing101.i234.me\/wordpress\/wp-json\/wp\/v2\/posts\/1398\/revisions\/1501"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/plumbing101.i234.me\/wordpress\/wp-json\/wp\/v2\/media\/1500"}],"wp:attachment":[{"href":"https:\/\/plumbing101.i234.me\/wordpress\/wp-json\/wp\/v2\/media?parent=1398"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/plumbing101.i234.me\/wordpress\/wp-json\/wp\/v2\/categories?post=1398"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/plumbing101.i234.me\/wordpress\/wp-json\/wp\/v2\/tags?post=1398"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}