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Proudly Serving New Hampshire Homeowners

At GSMS, we are proud to serve New Hampshire with our comprehensive range of HVAC and plumbing services.

As a family-owned business with 35+ years of experience, we have built a reputation for excellence, reliability, and outstanding customer care. Our skilled technicians are dedicated to providing top-quality repairs, installations, and maintenance tailored to meet the unique needs of New Hampshire homeowners.

Explore our service area below, read reviews in your city, and see why homeowners across New Hampshire trust GSMS for their HVAC and plumbing needs.

Contact us online today or call 603-424-8258 to schedule your service and experience the GSMS difference.

Recent Jobs and Reviews

Rated 5.0 out of 5 stars based on 331 customer reviews

Customers say: The recent reviews exhibit a predominantly positive sentiment, with recurring themes of satisfaction, professionalism, and expertise. Customers express gratitude, recommend the company, and acknowledge the quality of the work performed. Positive reviews frequently mention friendly and knowledgeable technicians, timely responses, and efficient service. Negative reviews are minimal and do not represent a clear, recurring trend. Overall, the reviews suggest a positive experience with the company, with many customers expressing satisfaction with their HVAC and plumbing needs.

Job Locations and Reviews

Preventative maintenance completed on boiler. I needed to replace the expansion tank, relief valve, and tridicator gauge. Thank you.
Preventative maintenance completed on boiler. I needed to replace the expansion tank, relief valve, and tridicator gauge. Thank you.
Jack D.
Jack D. Checked in
Preventative maintenance completed on boiler. I needed to replace the expansion tank, relief valve, and tridicator gauge. Thank you.
Manchester, NH 03104
Mark D.
Mark D. Checked in
Replaced kohler flapper
Nashua, NH 03064
Pm on boiler changed electrodes
Pm on boiler changed electrodes
Mark D.
Mark D. Checked in
Pm on boiler changed electrodes
Canterbury, NH 03224
Jack D.
Jack D. Checked in
Replace faulty boiler expansion tank. Replace sticking relief valve. Replace faulty temperature and pressure gauge.
Manchester, NH 03102
Completed the gas furnace maintenance today. The tenant said that the heat wasn’t working, but upon arrival the heat was on. Jeff found that the air filter was extremely dirty. We replaced it with a new filter that was there. In the furnace, I started off with checking all the wiring connections and everything looked good. I pulled and cleaned the flame sensor. I noticed that some point water had been leaking inside of the unit, but there was no active leaks just stains. I checked incoming and outgoing gas pressures and those were according to manufacture specifications. I performed a combustion analyzer test that tests the units CO, CO2 and oxygen levels and furnace was running great.
Completed the gas furnace maintenance today. The tenant said that the heat wasn’t working, but upon arrival the heat was on. Jeff found that the air filter was extremely dirty. We replaced it with a new filter that was there. In the furnace, I started off with checking all the wiring connections and everything looked good. I pulled and cleaned the flame sensor. I noticed that some point water had been leaking inside of the unit, but there was no active leaks just stains. I checked incoming and outgoing gas pressures and those were according to manufacture specifications. I performed a combustion analyzer test that tests the units CO, CO2 and oxygen levels and furnace was running great.
Qwentin G.
Qwentin G. Checked in
Completed the gas furnace maintenance today. The tenant said that the heat wasn’t working, but upon arrival the heat was on. Jeff found that the air filter was extremely dirty. We replaced it with a new filter that was there. In the furnace, I started off with checking all the wiring connections and everything looked good. I pulled and cleaned the flame sensor. I noticed that some point water had been leaking inside of the unit, but there was no active leaks just stains. I checked incoming and outgoing gas pressures and those were according to manufacture specifications. I performed a combustion analyzer test that tests the units CO, CO2 and oxygen levels and furnace was running great.
Manchester, NH 03102
Jack D.
Jack D. Checked in
I re arranged the control woring for the system. I found a gang of wired sharing a hole with line voltage wiring. I think this was the problem. I also grounded a zone stat to common. Covered under system warranty, thank you!
Bedford, NH 03110
I completed the gas furnace maintenance. I started off with checking all the electrical connections and the capacitors and everything looked good. I replaced the air filter. I vacuumed out the filter box and the furnace cabinet. I pulled and cleaned the flame sensor. When I checked incoming gas pressures the pressure was low so I had to adjust the regulator. I adjusted outgoing gas pressures after and everything was according to manufacturer specifications. Lastly, I performed a combustion analyzer test that checks the units CO, CO2 and oxygen levels and the furnace was running great.
I completed the gas furnace maintenance. I started off with checking all the electrical connections and the capacitors and everything looked good. I replaced the air filter. I vacuumed out the filter box and the furnace cabinet. I pulled and cleaned the flame sensor. When I checked incoming gas pressures the pressure was low so I had to adjust the regulator. I adjusted outgoing gas pressures after and everything was according to manufacturer specifications. Lastly, I performed a combustion analyzer test that checks the units CO, CO2 and oxygen levels and the furnace was running great.
Qwentin G.
Qwentin G. Checked in
I completed the gas furnace maintenance. I started off with checking all the electrical connections and the capacitors and everything looked good. I replaced the air filter. I vacuumed out the filter box and the furnace cabinet. I pulled and cleaned the flame sensor. When I checked incoming gas pressures the pressure was low so I had to adjust the regulator. I adjusted outgoing gas pressures after and everything was according to manufacturer specifications. Lastly, I performed a combustion analyzer test that checks the units CO, CO2 and oxygen levels and the furnace was running great.
Bedford, NH 03110
Mark D.
Mark D. Checked in
Cleaned flame sensor and electrodes.
Manchester, NH 03103
I started off with completing the maintenance for the unit in the garage. I started off with checking all the wiring connections and everything looked good. I pulled and cleaned the flame sensor. I replaced the air filter. I vacuumed out the filter box and the furnace. Checked incoming and outgoing gas pressures and those were according to manufacturer specifications. I performed a combustion analyzer test that checks the units CO, CO2 and oxygen levels and the unit was running good. Couple things I found was that the inducer motor capacitor is starting to fail. I found that the burner tubes are very rusty. I found that the trap on the unit has been leaking water for a while. I found that the fitting that connects the inducer motor to the exhaust vent pipe was leaking CO in the furnace cabinet. I sealed it up with high temp silicon and vent tape and tested it, there is no more CO present. I would highly recommend making all those repairs especially the connector for the inducer motor i
I started off with completing the maintenance for the unit in the garage. I started off with checking all the wiring connections and everything looked good. I pulled and cleaned the flame sensor. I replaced the air filter. I vacuumed out the filter box and the furnace. Checked incoming and outgoing gas pressures and those were according to manufacturer specifications. I performed a combustion analyzer test that checks the units CO, CO2 and oxygen levels and the unit was running good. Couple things I found was that the inducer motor capacitor is starting to fail. I found that the burner tubes are very rusty. I found that the trap on the unit has been leaking water for a while. I found that the fitting that connects the inducer motor to the exhaust vent pipe was leaking CO in the furnace cabinet. I sealed it up with high temp silicon and vent tape and tested it, there is no more CO present. I would highly recommend making all those repairs especially the connector for the inducer motor i
Qwentin G.
Qwentin G. Checked in
I started off with completing the maintenance for the unit in the garage. I started off with checking all the wiring connections and everything looked good. I pulled and cleaned the flame sensor. I replaced the air filter. I vacuumed out the filter box and the furnace. Checked incoming and outgoing gas pressures and those were according to manufacturer specifications. I performed a combustion analyzer test that checks the units CO, CO2 and oxygen levels and the unit was running good. Couple things I found was that the inducer motor capacitor is starting to fail. I found that the burner tubes are very rusty. I found that the trap on the unit has been leaking water for a while. I found that the fitting that connects the inducer motor to the exhaust vent pipe was leaking CO in the furnace cabinet. I sealed it up with high temp silicon and vent tape and tested it, there is no more CO present. I would highly recommend making all those repairs especially the connector for the inducer motor i
Bedford, NH 03110
Determined there is another run off of the plenum that goes up to the second floor for his son's bedroom that we need to cut in a damper for. Then is flexible with timing we can plan on coming back worst case he can give us the garage code to get in. Also installed remote room air sensor for S40 system for the second floor.
Determined there is another run off of the plenum that goes up to the second floor for his son's bedroom that we need to cut in a damper for. Then is flexible with timing we can plan on coming back worst case he can give us the garage code to get in. Also installed remote room air sensor for S40 system for the second floor.
Jack D.
Jack D. Checked in
Determined there is another run off of the plenum that goes up to the second floor for his son's bedroom that we need to cut in a damper for. Then is flexible with timing we can plan on coming back worst case he can give us the garage code to get in. Also installed remote room air sensor for S40 system for the second floor.
Nashua, NH 03062
Review
Arrived on time. Work was completed timely. Cleaned up afterwards. Very pleased with the service.
Charlie - New Boston, NH 03070
Review
GSMS is a great Family owned Company to work with. I am very happy with my new Boiler heating system. Zak explained all my options and was prompt to call back with any questions I had. Adam, the lead Technician was outstanding with the installation. Gina was great coordinating the scheduling. Mark also came out for a final inspection. You can tell they take pride in their work! I would definitely recommend them.
Sandy - Nashua, NH 03060
Review
Jack was prompt and did a great job tuning our furnace.
Vincent - Nashua, NH 03064
Review
Very happy with the job done.
Barb - Merrimack, NH 03054
Review
Did annual maintenance on the furnaces so we are all set for winter!
Lori B - Nashua, NH 03060
Review
Did annual maintenance on the furnaces so we are all set for winter!
Lori B - Nashua, NH 03060
Review
Great seeing Mark again.
Bob - Nashua, NH 03062
Review
As always, your guys are on time, polite, efficient and friendly. No worries when any of your crew is here, or at the office texting. Thank you GSMS. Susan
Susan - Salem, NH 03079
Review
Excellent service!
Darlene - Manchester, NH 03109
Review
Very happy with the service. Technician was great!!!!
Susan - Hooksett, NH 03106
Review
Love dealing with this company. Their techs are always prompt, efficient and courteous. We've been happy to be their customer since 2010.
Skip Sagris - Bow, NH 03304
Response from GSMS Air•Heating•Plumbing:

Thank you so much for the kind words and for being part of the GSMS family since 2010! It means the world to us to have earned your trust over the years. I’m proud of our team for continuing to deliver the kind of service that keeps clients like you coming back. We truly appreciate your loyalty and support. – Zak D., Second-Generation Owner

Review
Qwentin was on time, very friendly and professional. He was able to identify the issue, communicate it effectively, and then fix it. Highly recommend.
Phil Cutler - Bedford, NH 03110
Response from GSMS Air•Heating•Plumbing:

Thank you so much for the kind words and for trusting GSMS to take care of your home. Qwentin is a rising star on our team, and it means a lot to hear that his professionalism and communication made a strong impression. As a local, family-run business, we’re grateful for your recommendation and honored to have earned your trust. – Zak D., Second-Generation Owner

Review
Great water heater service. On time and professional l He gave me some helpful tips on other water related issues. Highly recommend GSMS.
Katherine Turner - Exeter, NH 03833
Response from GSMS Air•Heating•Plumbing:

Thank you for the great review! I’m glad to hear our Specialist was able to get your water heater squared away and offer some extra tips while he was there. We always aim to go beyond just the repair, and I really appreciate you taking the time to share your experience. Thanks for choosing GSMS — it means a lot to our family and our team. – Zak D., Second-Generation Owner

Review
David DiNardo - Bedford, NH 03110
Response from GSMS Air•Heating•Plumbing:

Thank you for the 5 stars, David! We really appreciate you choosing GSMS and supporting our family-run team. If there’s ever anything more we can do for you, don’t hesitate to reach out. – Zak D., Second-Generation Owner

Review
claire lafond - Merrimack, NH 03054
Response from GSMS Air•Heating•Plumbing:

Thank you so much for the 5 stars, Claire! We’re grateful for your support and truly appreciate you choosing GSMS. It means a lot to our family and our entire team. – Zak D., Second-Generation Owner

Review
Great work, fair prices.
Tom Grasse - Manchester, NH 03104
Response from GSMS Air•Heating•Plumbing:

We thank you for sharing your positive experience. It made our day.

Review
top notch service, always professional. would recommend to anyone needing HVAC service, repair or install.
Ben Bouchard - Nashua, NH 03062
Response from GSMS Air•Heating•Plumbing:

It was a pleasure serving you and your family. Thank you for sharing your kind words with us. It means the world to us and to our entire team!

Review
Had an issue with our heat pump. Reached out for assistance and they had someone on site that afternoon. Problem was resolved quickly. Super friendly service. The tech was exceptionally friendly and an excellent communicator. Highly recommend
Mark Cooke - Greenland, NH 03840
Response from GSMS Air•Heating•Plumbing:

It was a pleasure serving you and your family. Thank you for sharing your kind words with us. It means the world to us and to our entire team!

Review
Adam, Quin and Mark did a wonderful job installing my replacement oil boiler and oil tank. I have trusted GSM for 3 installs at my house because of their professionalism, workmanship, honesty, transparency and integrity for how they conduct their family business. Everyone who has worked at my house has always been informative, on time and respectful. I would recommend GSM to anyone who needs to have major plumbing or heating/cooling done in their home. Gina in customer service is the best at relaying information and gets back to you in a timely fashion. Zak is wonderful to work with and the entire team at GSM treats you with kindness. Thank you again for another wonderful experience because when it comes to your home it is one of the largest investments you will make in your life, and I trust GSM to be there for me in the future.
Kimberly Cichon - Newmarket, NH 03857
Response from GSMS Air•Heating•Plumbing:

We thank you for sharing your positive experience. It made our day.

Review
As usual, Jack's work is stellar.
Bob Bedrosian - Merrimack, NH 03054
Response from GSMS Air•Heating•Plumbing:

We are so glad to hear that you had a good experience.

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