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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 316 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

Completed the maintenance on all six gas boilers. Pulled all the burner tubes and cleaned them. Cleaned the pilot assembly as well. Gas sniffed all the pilot tube connections, and found no leaks. Tested incoming and outgoing gas pressure. Performed a combustion analyzer test that checks for CO, CO2 and oxygen levels.
Completed the maintenance on all six gas boilers. Pulled all the burner tubes and cleaned them. Cleaned the pilot assembly as well. Gas sniffed all the pilot tube connections, and found no leaks. Tested incoming and outgoing gas pressure. Performed a combustion analyzer test that checks for CO, CO2 and oxygen levels.
Jack D.
Jack D. Checked in
Completed the maintenance on all six gas boilers. Pulled all the burner tubes and cleaned them. Cleaned the pilot assembly as well. Gas sniffed all the pilot tube connections, and found no leaks. Tested incoming and outgoing gas pressure. Performed a combustion analyzer test that checks for CO, CO2 and oxygen levels.
Manchester, NH 03102
Jack D.
Jack D. Checked in
Furnace PM. Everything went great. No issues, thank you!
Manchester, NH 03102
Installation of a single-zone mini-split heat pump system to provide the basement with heating and cooling. A wall-mounted indoor unit will be installed on the exterior basement wall. We will core through the concrete foundation to allow the lines and condensate to exit to the exterior of the home. The outdoor unit will be mounted to the foundation with a wall bracket mount. All electrical work will be completed by the client's electrician. We request that the electrical circuit for the system has a dedicated surge protector or that the home has a whole-home surge protector. Important Note: This is a low-temp unit, designed to provide highly efficient heating performance even in low outdoor temperatures.
Installation of a single-zone mini-split heat pump system to provide the basement with heating and cooling. A wall-mounted indoor unit will be installed on the exterior basement wall. We will core through the concrete foundation to allow the lines and condensate to exit to the exterior of the home. The outdoor unit will be mounted to the foundation with a wall bracket mount. All electrical work will be completed by the client's electrician. We request that the electrical circuit for the system has a dedicated surge protector or that the home has a whole-home surge protector. Important Note: This is a low-temp unit, designed to provide highly efficient heating performance even in low outdoor temperatures.
Adam P.
Adam P. Checked in
Installation of a single-zone mini-split heat pump system to provide the basement with heating and cooling. A wall-mounted indoor unit will be installed on the exterior basement wall. We will core through the concrete foundation to allow the lines and condensate to exit to the exterior of the home. The outdoor unit will be mounted to the foundation with a wall bracket mount. All electrical work will be completed by the client's electrician. We request that the electrical circuit for the system has a dedicated surge protector or that the home has a whole-home surge protector. Important Note: This is a low-temp unit, designed to provide highly efficient heating performance even in low outdoor temperatures.
East Kingston, NH 03827
Jack D.
Jack D. Checked in
Heat in living room left on due to hallway stat being on when it is usually left off for cooling.
Londonderry, NH 03053
Did home club visit for gas furnace and boiler.Both check out fine.
Did home club visit for gas furnace and boiler.Both check out fine.
Mark D.
Mark D. Checked in
Did home club visit for gas furnace and boiler.Both check out fine.
Bedford, NH 03110
Jack D.
Jack D. Checked in
Today I analyzed the boiler in the home. I found the pump neutral wired to L1 on the zone board, I switched that. I noticed that all of the pumps are on the return side, there are no zone valves present. This is what is causing zones to heat up when they aren't supposed to. This is also causing the issue with the first floor heat not feeling as warm, especially the bathroom.
Manchester, NH 03102
Litchfield, NH - Completed the maintenance on the oil boiler. I replaced the oil filter, the pump strainer, the nozzle and the electrodes. I removed the flue pipe and brushed and vacuumed the heat exchanger. The 90° elbow and the reducer that sits in the chimney both broke so that had to be replaced. I ran the unit and performed a combustion analyzer test. This checks for CO, CO2 and oxygen levels and everything was running great. I also had zero smoke.
Qwentin G.
Qwentin G. Checked in
Completed the maintenance on the oil boiler. I replaced the oil filter, the pump strainer, the nozzle and the electrodes. I removed the flue pipe and brushed and vacuumed the heat exchanger. The 90° elbow and the reducer that sits in the chimney both broke so that had to be replaced. I ran the unit and performed a combustion analyzer test. This checks for CO, CO2 and oxygen levels and everything was running great. I also had zero smoke.
Litchfield, NH 03052
Adam P.
Adam P. Checked in
Installation of a single-zone mini-split system to provide cooling and heating to the new addition space. Finished space of 12' x 13'. Unit will be wall-mounted and the outdoor unit will be placed on the side of the addition. Lines will be encased in our CoverGuard product on the exterior. Scott Woodbury will provide electrician to install dedicated 240V circuit needed.
Nashua, NH 03062
Mark D.
Mark D. Checked in
Bad press coup
Nashua, NH 03062
Jack D.
Jack D. Checked in
Replacement of the existing touch-free toilet with our most popular toilet, the Cimarron.
Stratham, NH 03885
Review
Service
Guimont - Manchester, NH 03103
Review
Excellent Service!
E Z - Manchester, NH 03102
Review
Quick service call to replace thermostat. Done in about 15 minutes, explained the workings. Very satisfied Great service as usual
Joseph - Merrimack, NH 03054
Review
Our furnace kept shutting off. Mark identified the issue and resolved the problem. Very much appreciate the service!
Oakwood Prop - Milford, NH 03055
Review
Jack was polite and very neat.
Sharon - Merrimack, NH 03054
Review
We have been working with GSMS for 8 years. They provide the best service for installs and maintenance. The people are very professional, friendly and do great work. Today Qwentin was the tech doing the service maintenance. This young man came at the time scheduled, knew what he was doing and did excellent work. If you are in need for heating, air conditioning and plumbing work, this is the company for you!
Claire - Merrimack, NH 03054
Review
Jack did a great job. Provided a lot of good information. Thank you
Don - Merrimack, NH 03054
Review
Excellent service
Kathleen - Merrimack, NH 03054
Review
Excellent Service
Sharon - Merrimack, NH 03054
Review
Excellent
Sharon - Merrimack, NH 03054
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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