Why Does My Tankless Water Heater Sometimes Turn Cold?
You’re in the shower, enjoying steady hot water—when suddenly the temperature drops, and you’re hit with a blast of cold. For many Federal Way homeowners, this “cold water sandwich” effect is a common frustration. The good news? It usually points to issues that can be identified and fixed.
At 2 Sons Plumbing and Sewer Federal Way, we’ve helped countless families restore reliable hot water. Our licensed plumbers know the ins and outs of tankless water heater systems, and we’re here to explain what’s happening, why it occurs, and what you can do about it.
Common Reasons Tankless Water Heaters Run Cold
When your tankless water heater cuts out unexpectedly, it often comes down to one of these issues:
- Not enough water flow – Tankless units need a minimum flow rate to fire up. If the faucet or shower isn’t running enough water, the system can shut off mid-use.
- Scale buildup – Minerals in Federal Way’s water supply can accumulate inside the unit, blocking heat exchange and reducing performance.
- Temperature mixing – If multiple fixtures are in use or the thermostat is set incorrectly, cold water can sneak into the line.
DIY Steps You Can Try
Before calling for professional help, try these simple checks:
- Run another faucet – Boosting flow may help the unit maintain consistent heating.
- Check the thermostat – Make sure your unit is set to at least 120°F for safe, reliable performance.
- Flush and descale annually – Hard water minerals can build up quickly. A regular flush helps your system run smoothly.
When to Call a Professional
While minor hiccups can sometimes be resolved at home, call a licensed plumber if you notice:
- A gas odor near the unit
- Error codes on the display screen
- Repeated shutdowns even after basic troubleshooting
Tankless water heaters are advanced systems. Attempting to repair gas or electrical components without training can be dangerous and worsen the problem. Our experienced team has the right tools and knowledge to safely diagnose the issue.
What It Might Cost
The cost depends on the issue, but here’s a general guide for Federal Way homeowners:
- Descaling service: $250–$500
- Valve or component replacement: Varies depending on part and brand
At 2 Sons Plumbing and Sewer Federal Way, we believe in transparency. We’ll walk you through the problem, explain your options in plain language, and give you upfront pricing so there are no surprises.
Restore Your Hot Water Comfort with 2 Sons Plumbing and Sewer Federal Way
Losing hot water in the middle of a shower or chore is more than just an inconvenience—it disrupts your day and your comfort.
At 2 Sons Plumbing and Sewer Federal Way, we’ve built our reputation on fast response times, honest communication, and quality repairs you can trust. Call us today at (206) 487-1757. With 2 Sons Plumbing and Sewer Federal Way, you’ll get expert service, clear answers, and the peace of mind that your hot water is back to running exactly how it should.
Jackie Johanson
3 weeks ago
⭐⭐⭐⭐⭐
I had a project that required a quick turnaround for some temporary top-out plumbing, and Two Sons Plumbing was incredibly responsive from the start. They came out quickly to provide a quote and, even during what I know is their peak season, they prioritized getting my project scheduled. That level of customer service was greatly appreciated.
The quote was a bit of sticker shock, but that’s simply the reality of the Seattle market—not a reflection of their service. What really stood out was that the same person who came out to provide the estimate also completed the work. It meant I didn’t have to explain everything twice, and we’d already built a level of trust before the job even started.
The quality of the work was excellent, and they even went above and beyond by replacing a damaged toilet lid at no extra charge. Small gestures like that make a big difference.
If you’re looking for a fast, reliable plumbing company that does quality work and takes great care of its customers, I’d definitely recommend Two Sons Plumbing.
I had a project that required a quick turnaround for some temporary top-out plumbing, and Two Sons Plumbing was incredibly responsive from the start. They came out quickly to provide a quote and, even during what I know is their peak season, they prioritized getting my project scheduled. That level of customer service was greatly appreciated.
The quote was a bit of sticker shock, but that’s simply the reality of the Seattle market—not a reflection of their service. What really stood out was that the same person who came out to provide the estimate also completed the work. It meant I didn’t have to explain everything twice, and we’d already built a level of trust before the job even started.
The quality of the work was excellent, and they even went above and beyond by replacing a damaged toilet lid at no extra charge. Small gestures like that make a big difference.
If you’re looking for a fast, reliable plumbing company that does quality work and takes great care of its customers, I’d definitely recommend Two Sons Plumbing.
Jackie Johanson
3 weeks ago
⭐⭐⭐⭐⭐
I had a project that required a quick turnaround for some temporary top-out plumbing, and Two Sons Plumbing was incredibly responsive from the start. They came out quickly to provide a quote and, even during what I know is their peak season, they prioritized getting my project scheduled. That level of customer service was greatly appreciated.
The quote was a bit of sticker shock, but that’s simply the reality of the Seattle market—not a reflection of their service. What really stood out was that the same person who came out to provide the estimate also completed the work. It meant I didn’t have to explain everything twice, and we’d already built a level of trust before the job even started.
The quality of the work was excellent, and they even went above and beyond by replacing a damaged toilet lid at no extra charge. Small gestures like that make a big difference.
If you’re looking for a fast, reliable plumbing company that does quality work and takes great care of its customers, I’d definitely recommend Two Sons Plumbing.
I had a project that required a quick turnaround for some temporary top-out plumbing, and Two Sons Plumbing was incredibly responsive from the start. They came out quickly to provide a quote and, even during what I know is their peak season, they prioritized getting my project scheduled. That level of customer service was greatly appreciated.
The quote was a bit of sticker shock, but that’s simply the reality of the Seattle market—not a reflection of their service. What really stood out was that the same person who came out to provide the estimate also completed the work. It meant I didn’t have to explain everything twice, and we’d already built a level of trust before the job even started.
The quality of the work was excellent, and they even went above and beyond by replacing a damaged toilet lid at no extra charge. Small gestures like that make a big difference.
If you’re looking for a fast, reliable plumbing company that does quality work and takes great care of its customers, I’d definitely recommend Two Sons Plumbing.
Brad Poirier
1 month ago
Had a great experience with 2 Sons Plumbing and Sewer and the representative they sent, Jake. They did a fantastic job communicating through email, text, and calls, sending reminders when the appointment was and who their representative was, and when he would arrive. Jake did a wonderful job hunting done where the leak was coming from and explaining the options I had for getting the leak repaired. When he left he emailed my receipt, pictures he had taken of my water lines under the house, and the options I could use to compete locating and repairing the leak. Highly recommend them. A very professional outfit.
Brad Poirier
1 month ago
Had a great experience with 2 Sons Plumbing and Sewer and the representative they sent, Jake. They did a fantastic job communicating through email, text, and calls, sending reminders when the appointment was and who their representative was, and when he would arrive. Jake did a wonderful job hunting done where the leak was coming from and explaining the options I had for getting the leak repaired. When he left he emailed my receipt, pictures he had taken of my water lines under the house, and the options I could use to compete locating and repairing the leak. Highly recommend them. A very professional outfit.
Jennifer Suemnicht
3 months ago
I asked some of my real estate colleagues who people have been using for plumbing repairs lately and several said “2 Sons”! So friendly and responsive. Came out right away for an estimate, had the best follow up, came in with the best price, and got me on the schedule and got the work done on the very next day! Everyone I spoke with was friendly and fantastic! Highly recommend!
Jennifer Suemnicht
3 months ago
I asked some of my real estate colleagues who people have been using for plumbing repairs lately and several said “2 Sons”! So friendly and responsive. Came out right away for an estimate, had the best follow up, came in with the best price, and got me on the schedule and got the work done on the very next day! Everyone I spoke with was friendly and fantastic! Highly recommend!
Katy Garner
4 months ago
We had a mystery leak per our meter reading. Riley and Riley saved the day. They promptly discovered the issue, resolved and repaired our pipes in one service call. They were quick, thorough and entirely delightful. They took the time to talk me through the job. I felt heard, safe and comfortable with the two of them in my house. For my next plumbing disaster I hope to get ‘The Riley’s’; but know, whoever comes will be excellent. Thanks 2 Sons!
Katy Garner
4 months ago
We had a mystery leak per our meter reading. Riley and Riley saved the day. They promptly discovered the issue, resolved and repaired our pipes in one service call. They were quick, thorough and entirely delightful. They took the time to talk me through the job. I felt heard, safe and comfortable with the two of them in my house. For my next plumbing disaster I hope to get ‘The Riley’s’; but know, whoever comes will be excellent. Thanks 2 Sons!
Aaron Sutter
4 months ago
2 Sons are my go to plumbers and I recommend them to friends and family looking for a recommendation.
2 Sons had my tenant's water heater replaced in the same day I called them! Justin and his apprentice were awesome! This wasn't a "quick" replacement in the garage - they had to figure out how to squeeze in the water heater through a tight crawl space on their hands and knees under furnace ducting.
Justin was knowledgeable and helpful in troubleshooting different replacement scenarios. He was kind and patient with my number of questions. He never once complained to me about the undesirable placement of the water heater under the house. My tenant even commented to me how kind Justin was to her.
Thank you for making this a quick and easy fix!
2 Sons had my tenant's water heater replaced in the same day I called them! Justin and his apprentice were awesome! This wasn't a "quick" replacement in the garage - they had to figure out how to squeeze in the water heater through a tight crawl space on their hands and knees under furnace ducting.
Justin was knowledgeable and helpful in troubleshooting different replacement scenarios. He was kind and patient with my number of questions. He never once complained to me about the undesirable placement of the water heater under the house. My tenant even commented to me how kind Justin was to her.
Thank you for making this a quick and easy fix!
Aaron Sutter
4 months ago
2 Sons are my go to plumbers and I recommend them to friends and family looking for a recommendation.
2 Sons had my tenant's water heater replaced in the same day I called them! Justin and his apprentice were awesome! This wasn't a "quick" replacement in the garage - they had to figure out how to squeeze in the water heater through a tight crawl space on their hands and knees under furnace ducting.
Justin was knowledgeable and helpful in troubleshooting different replacement scenarios. He was kind and patient with my number of questions. He never once complained to me about the undesirable placement of the water heater under the house. My tenant even commented to me how kind Justin was to her.
Thank you for making this a quick and easy fix!
2 Sons had my tenant's water heater replaced in the same day I called them! Justin and his apprentice were awesome! This wasn't a "quick" replacement in the garage - they had to figure out how to squeeze in the water heater through a tight crawl space on their hands and knees under furnace ducting.
Justin was knowledgeable and helpful in troubleshooting different replacement scenarios. He was kind and patient with my number of questions. He never once complained to me about the undesirable placement of the water heater under the house. My tenant even commented to me how kind Justin was to her.
Thank you for making this a quick and easy fix!
Oksana Naidu
4 months ago
Highly recommend 2 Sons. We had a leak in the master bath due to some malfunctioning fixtures and needed to install shut off valves on the hot and cold water lines to prevent further leaks while we waited on the faulty part replacements to be delivered. It was a treat to work with a professional and honest plumbing company that also does quality work. A great experience from first call to post-completion follow ups. Marcos, who was assigned to our job, was just awesome - thorough, efficient, knowledgeable, professional, courteous and helpful. He took his time to fully assess the issue, provided great options and then quickly repaired the problem. Thanks so much for great service in a stressful situation.
Oksana Naidu
4 months ago
Highly recommend 2 Sons. We had a leak in the master bath due to some malfunctioning fixtures and needed to install shut off valves on the hot and cold water lines to prevent further leaks while we waited on the faulty part replacements to be delivered. It was a treat to work with a professional and honest plumbing company that also does quality work. A great experience from first call to post-completion follow ups. Marcos, who was assigned to our job, was just awesome - thorough, efficient, knowledgeable, professional, courteous and helpful. He took his time to fully assess the issue, provided great options and then quickly repaired the problem. Thanks so much for great service in a stressful situation.
Happy Lemon
5 months ago
We had an outstanding experience with this company! They provided incredibly fast, careful, and professional service for our commercial business. From start to finish, their customer service was absolutely excellent-responsive, friendly, and truly attentive to our needs.
A special thank you to our technician, ADAM, who did an exceptional job fixing our clogged hand sink. He was knowledgeable, efficient, and extremely professional & polite. He quickly resolved it with great skill and attention to detail.
Highly recommended!
A special thank you to our technician, ADAM, who did an exceptional job fixing our clogged hand sink. He was knowledgeable, efficient, and extremely professional & polite. He quickly resolved it with great skill and attention to detail.
Highly recommended!
Happy Lemon
5 months ago
We had an outstanding experience with this company! They provided incredibly fast, careful, and professional service for our commercial business. From start to finish, their customer service was absolutely excellent-responsive, friendly, and truly attentive to our needs.
A special thank you to our technician, ADAM, who did an exceptional job fixing our clogged hand sink. He was knowledgeable, efficient, and extremely professional & polite. He quickly resolved it with great skill and attention to detail.
Highly recommended!
A special thank you to our technician, ADAM, who did an exceptional job fixing our clogged hand sink. He was knowledgeable, efficient, and extremely professional & polite. He quickly resolved it with great skill and attention to detail.
Highly recommended!
Louisa
5 months ago
Trung our tech and his apprentice Cole did a fantastic job yesterday. They worked tirelessly to replace our old CPVC pipes, install our new shower, and replace our kitchen sink. The job had a multitude of delays due our pipes not being plumb and some extra wall demo. They worked for at least 13+ hours yesterday and left our home at 11 pm. Trung wanted to ensure that we didn't have our water off longer than necessary. We could not be more thankful and grateful for their efforts in the rough in for our bathroom remodel. We look forward to having them back to install the shower/ tub combo, new bathroom faucet, and new toilet with a bidet seat. Trung always went out of his way to explain what was going on and helped us make informed decisions about our home. This is our 3rd or 4th time using 2 Sons and we couldn't recommend them more!
Update: Trung was extremely great with the final install! Unfortunately, there was a few mishaps with not communicating the right color of the shower/ tub combo and the hole for the toilet pipe not being wide enough for the toilet flange. Trung really went above and beyond to ensure we got the right parts and to cut the tile as best he could for the toilet to fit. He even had to double check our toilet because he thought he heard a leak. He even was able to replace our drain stopper and recommended a solution for making the tub drain match!
Update: Trung was extremely great with the final install! Unfortunately, there was a few mishaps with not communicating the right color of the shower/ tub combo and the hole for the toilet pipe not being wide enough for the toilet flange. Trung really went above and beyond to ensure we got the right parts and to cut the tile as best he could for the toilet to fit. He even had to double check our toilet because he thought he heard a leak. He even was able to replace our drain stopper and recommended a solution for making the tub drain match!
Louisa
5 months ago
Trung our tech and his apprentice Cole did a fantastic job yesterday. They worked tirelessly to replace our old CPVC pipes, install our new shower, and replace our kitchen sink. The job had a multitude of delays due our pipes not being plumb and some extra wall demo. They worked for at least 13+ hours yesterday and left our home at 11 pm. Trung wanted to ensure that we didn't have our water off longer than necessary. We could not be more thankful and grateful for their efforts in the rough in for our bathroom remodel. We look forward to having them back to install the shower/ tub combo, new bathroom faucet, and new toilet with a bidet seat. Trung always went out of his way to explain what was going on and helped us make informed decisions about our home. This is our 3rd or 4th time using 2 Sons and we couldn't recommend them more!
Update: Trung was extremely great with the final install! Unfortunately, there was a few mishaps with not communicating the right color of the shower/ tub combo and the hole for the toilet pipe not being wide enough for the toilet flange. Trung really went above and beyond to ensure we got the right parts and to cut the tile as best he could for the toilet to fit. He even had to double check our toilet because he thought he heard a leak. He even was able to replace our drain stopper and recommended a solution for making the tub drain match!
Update: Trung was extremely great with the final install! Unfortunately, there was a few mishaps with not communicating the right color of the shower/ tub combo and the hole for the toilet pipe not being wide enough for the toilet flange. Trung really went above and beyond to ensure we got the right parts and to cut the tile as best he could for the toilet to fit. He even had to double check our toilet because he thought he heard a leak. He even was able to replace our drain stopper and recommended a solution for making the tub drain match!
Kathy Cook
5 months ago
I have to say Bob was amazing!!! I had a clogged drain in my kitchen sink. Bob came in and took every precaution to be neat & clean. He explained to me what he was going to do and gave me the pricing and I agreed and he got to work. He was super kind and polite and fixed my drain issue. He was a pleasure to work with. I would highly recommend using 2 Sons!
Kathy Cook
5 months ago
I have to say Bob was amazing!!! I had a clogged drain in my kitchen sink. Bob came in and took every precaution to be neat & clean. He explained to me what he was going to do and gave me the pricing and I agreed and he got to work. He was super kind and polite and fixed my drain issue. He was a pleasure to work with. I would highly recommend using 2 Sons!
Emily Speakman
5 months ago
Had issues at home with water backup. Dave was prompt, professional, and genuinely kind. He communicated between myself and my landlord, explaining the issues and next steps. He quickly put an interim solution in place and outlined the long-term needs. Felt super reliable and easy to work with — highly recommend 2 Sons Plumbing and Sewer.
Emily Speakman
5 months ago
Had issues at home with water backup. Dave was prompt, professional, and genuinely kind. He communicated between myself and my landlord, explaining the issues and next steps. He quickly put an interim solution in place and outlined the long-term needs. Felt super reliable and easy to work with — highly recommend 2 Sons Plumbing and Sewer.
Services Provided:
PLUMBING:
SEWER :