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Our Service Area

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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 344 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

Jack D.
Jack D. Checked in
Replace Lennox pressure switch warranty. Thank you!
Manchester, NH 03104
Jack D.
Jack D. Checked in
Replace toilet tank gasket after hours. All set, thank you!
Manchester, NH 03104
Installed the new collector box and all gaskets. Installed the new trap as well and primed it. Ran the unit and checked for leaks and there was no leaks. Performed a combustion analyzer test that checks the units CO, CO2 and oxygen levels and everything was running great. Client signed up for home club. He wants us to come out in the fall to do his furnace maintenance and spring/summer to do the AC.
Installed the new collector box and all gaskets. Installed the new trap as well and primed it. Ran the unit and checked for leaks and there was no leaks. Performed a combustion analyzer test that checks the units CO, CO2 and oxygen levels and everything was running great. Client signed up for home club. He wants us to come out in the fall to do his furnace maintenance and spring/summer to do the AC.
Qwentin G.
Qwentin G. Checked in
Installed the new collector box and all gaskets. Installed the new trap as well and primed it. Ran the unit and checked for leaks and there was no leaks. Performed a combustion analyzer test that checks the units CO, CO2 and oxygen levels and everything was running great. Client signed up for home club. He wants us to come out in the fall to do his furnace maintenance and spring/summer to do the AC.
Concord, NH 03301
Bedford, NH - Installation of a new high-performance steam humidifier for the first-floor HVAC system. Scope of Work: The existing bypass humidifier will be disconnected, removed, and the ductwork opening will be properly patched. The new steam unit will be mounted on the wall near the furnace, with tubing routed to the steam dispersion tube inserted into the supply duct. A dedicated electrical circuit will be installed from the electrical panel to the humidifier location to power the steam generator. Controls: The steam unit will be wired directly to the existing Lennox S40 smart thermostat. This allows for precise, integrated control of humidity levels through the main system interface. Performance Note: While this unit is installed on the first-floor system, humidity naturally migrates. Therefore, the second floor should receive incidental humidification, although this is not a dedicated solution for that specific zone.
Adam P.
Adam P. Checked in
Installation of a new high-performance steam humidifier for the first-floor HVAC system. Scope of Work: The existing bypass humidifier will be disconnected, removed, and the ductwork opening will be properly patched. The new steam unit will be mounted on the wall near the furnace, with tubing routed to the steam dispersion tube inserted into the supply duct. A dedicated electrical circuit will be installed from the electrical panel to the humidifier location to power the steam generator. Controls: The steam unit will be wired directly to the existing Lennox S40 smart thermostat. This allows for precise, integrated control of humidity levels through the main system interface. Performance Note: While this unit is installed on the first-floor system, humidity naturally migrates. Therefore, the second floor should receive incidental humidification, although this is not a dedicated solution for that specific zone.
Bedford, NH 03110
Jack D.
Jack D. Checked in
Adjust radiant mixing valve & purge air from loop. Thank you!
Manchester, NH 03109
Qwentin G.
Qwentin G. Checked in
Mini split blower wheel was really dirty. Performed a deep cleaning on it. This involves removing all the plastic covering and placing a bib around it. I cleaned it with soap and hot water multiple times. Tested operation at the end and is running great.
Bow, NH 03304
Gas pressure test. We will schedule inspection and notify you. Thank you.
Gas pressure test. We will schedule inspection and notify you. Thank you.
Jack D.
Jack D. Checked in
Gas pressure test. We will schedule inspection and notify you. Thank you.
Manchester, NH 03104
Jack D.
Jack D. Checked in
Limit switch stuck open. Replaced and unit is operating as intended. Thank you.
Manchester, NH 03103
Qwentin G.
Qwentin G. Checked in
Replaced the mini splits vane motor for her son's bedroom. Tested operation and everything works as it should!
Durham, NH 03824
Adam P.
Adam P. Checked in
Cut 2x4 to reduce vibration
Auburn, NH 03032
Review
Excellent Service
Guimont - Londonderry, NH 03053
Review
Very nice and personable person. Explained everything to me in a way I could understand
Dave - Hooksett, NH 03106
Review
I never thought I’d meet anyone as cool nice and kind as Mark but Jack was amazing. He took on the dirty job.. No problem He was super communicative and explained everything. I’m really grateful to have Granite State Mechanical on speed dial.
Kathleen - Nashua, NH 03064
Review
Jack was once again on time, diagnosed the problem quickly and fixed it. All GSMS staff are courteous and extremely professional. I wouldn’t go with anyone else.
Ronald - Merrimack, NH 03054
Review
Excellent work
Turning - Manchester, NH 03103
Review
Great service!
Colleen - Manchester, NH 03104
Review
Working with GSMS was a fantastic experience. There was attention to detail from the estimate to the clean up at the end of the project. Especially during the planning process, Zak helped me evaluate different options, quickly readjusted as I changed my mind... without ANY pressure! Superior, prompt communication during the whole (and post) process.
Ethel - Londonderry, NH 03053
Review
No heat emergency situation handled immediately on a Sunday evening. Great service!
Paul - Amherst, NH 03031
Review
Excellent service
Paul - Nashua, NH 03062
Review
Qwentin did the annual maintenance on our furnaces. He checked everything thoroughly via checklist and itemized was done.
Lori B - Nashua, NH 03064
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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