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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 313 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

Measure for tub replacement
Measure for tub replacement
Mark D.
Mark D. Checked in
Measure for tub replacement
Concord, NH 03301
Jack D.
Jack D. Checked in
Clean inlet screen, remove and inspect flush cartridge, reinstall cartridge, adjust actuator according to instructions, and test flush. Lever from handler is no longer slipping off of actuator linkage. Vacuumed up water in tank and flushed multiple times and there was no more water.
Bedford, NH 03110
Qwentin G.
Qwentin G. Checked in
Found that the indoor display board is faulty. Tech-support told me I should replace both the display board and the main control board. We will reach out to you in the next couple days with an estimate to replace the boards.
Barrington, NH 03825
Mark D.
Mark D. Checked in
Check water pressure 65 psi after pressure reducing valve.I would recommend replacing pressure reducing valve it's over 20 years old. Average life is 8 to 12 years.Will check in hammer arrestor valve also
Merrimack, NH 03054
I completed the gas furnace maintenance today. I checked all electrical connections and everything looked good. I pulled and cleaned the flame sensor. The client replaced her air filter recently. Checked incoming and outgoing gas pressures and everything was according to manufacturer specifications. Lastly, I ran the unit in high and low fire and performed a combustion analyzer test to check for CO, CO2 and oxygen levels and everything was running great. I talked to the client about adding a UV light and a leak breaker on her water heater. I will email her over the estimates for those.
I completed the gas furnace maintenance today. I checked all electrical connections and everything looked good. I pulled and cleaned the flame sensor. The client replaced her air filter recently. Checked incoming and outgoing gas pressures and everything was according to manufacturer specifications. Lastly, I ran the unit in high and low fire and performed a combustion analyzer test to check for CO, CO2 and oxygen levels and everything was running great. I talked to the client about adding a UV light and a leak breaker on her water heater. I will email her over the estimates for those.
Qwentin G.
Qwentin G. Checked in
I completed the gas furnace maintenance today. I checked all electrical connections and everything looked good. I pulled and cleaned the flame sensor. The client replaced her air filter recently. Checked incoming and outgoing gas pressures and everything was according to manufacturer specifications. Lastly, I ran the unit in high and low fire and performed a combustion analyzer test to check for CO, CO2 and oxygen levels and everything was running great. I talked to the client about adding a UV light and a leak breaker on her water heater. I will email her over the estimates for those.
Merrimack, NH 03054
Bedford, NH - Pm on oil boiler replaced nozzle,filter and strainer,check boiler water good
Mark D.
Mark D. Checked in
Pm on oil boiler replaced nozzle,filter and strainer,check boiler water good
Bedford, NH 03110
Review
Our furnace kept shutting off. Mark identified the issue and resolved the problem. Very much appreciate the service!
Oakwood Prop - Milford, NH 03055
Replacement of the failed cast-iron boiler with a new cast-iron boiler. The new boiler will re-use the existing chimney for venting. The two-zone setup will remain, with a dedicated circulator for the system and two new zone valves to control each zone. The existing thermostats will remain in place. A new coated oil line will be installed, as the existing one is unsleeved and buried in the concrete slab. Since the oil line will be vertical, our Tigerloop system will be installed to ensure air-free oil enters into the new boiler.
Replacement of the failed cast-iron boiler with a new cast-iron boiler. The new boiler will re-use the existing chimney for venting. The two-zone setup will remain, with a dedicated circulator for the system and two new zone valves to control each zone. The existing thermostats will remain in place. A new coated oil line will be installed, as the existing one is unsleeved and buried in the concrete slab. Since the oil line will be vertical, our Tigerloop system will be installed to ensure air-free oil enters into the new boiler.
Adam P.
Adam P. Checked in
Replacement of the failed cast-iron boiler with a new cast-iron boiler. The new boiler will re-use the existing chimney for venting. The two-zone setup will remain, with a dedicated circulator for the system and two new zone valves to control each zone. The existing thermostats will remain in place. A new coated oil line will be installed, as the existing one is unsleeved and buried in the concrete slab. Since the oil line will be vertical, our Tigerloop system will be installed to ensure air-free oil enters into the new boiler.
Manchester, NH 03103
Mark D.
Mark D. Checked in
Clean site glass and gaskets,remove probe from low water cut off and cleaned.
Milford, NH 03055
Flame sensor wire broke. Bolt snapped that connects inducer to the gas pipe. Need to order a new flame sensor cable and get a new bolt. Locked out and tagged out the boiler until those parts get replaced.
Flame sensor wire broke. Bolt snapped that connects inducer to the gas pipe. Need to order a new flame sensor cable and get a new bolt. Locked out and tagged out the boiler until those parts get replaced.
Jack D.
Jack D. Checked in
Flame sensor wire broke. Bolt snapped that connects inducer to the gas pipe. Need to order a new flame sensor cable and get a new bolt. Locked out and tagged out the boiler until those parts get replaced.
Londonderry, NH 03053
Review
Jack was polite and very neat.
Sharon - Merrimack, NH 03054
Jack D.
Jack D. Checked in
Replace bathroom faucet.
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
Qwentin serviced our furnace and installed our new Nest unit. He was friendly, attentive and thorough
Barry - Manchester, NH 03109
Review
Only great service from Jack with GSMS. Longtime customer!
Michelle - Manchester, NH 03104
Review
Qwentin performed annual maintenance on our furnace. He kept us informed on how the process was going and closed up the basement when the work was completed. A very professional job!
Lori B - Hollis, NH 03049
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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