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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 323 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

Mark D.
Mark D. Checked in
Replace flapper in toilet. Look at toilet that appears to be leaking. We could not find anything. Please keep an eye on it and if you find a leak you are better off to put a new toilet in given the age of the toilet and the parts it already needs to have replaced.
Merrimack, NH 03054
I completed the gas combi boiler maintenance today. I started off with cleaning the heat exchanger. I cleaned it with vinegar and a Scotch-Brite pad. I rinsed it out after with water. I pulled the trap and I cleaned it and primed it. I pulled the flame sensor and cleaned that as well. Lastly I performed a combustion analyzer test that checks for CO, CO2 and oxygen levels and the boiler was running great!
I completed the gas combi boiler maintenance today. I started off with cleaning the heat exchanger. I cleaned it with vinegar and a Scotch-Brite pad. I rinsed it out after with water. I pulled the trap and I cleaned it and primed it. I pulled the flame sensor and cleaned that as well. Lastly I performed a combustion analyzer test that checks for CO, CO2 and oxygen levels and the boiler was running great!
Qwentin G.
Qwentin G. Checked in
I completed the gas combi boiler maintenance today. I started off with cleaning the heat exchanger. I cleaned it with vinegar and a Scotch-Brite pad. I rinsed it out after with water. I pulled the trap and I cleaned it and primed it. I pulled the flame sensor and cleaned that as well. Lastly I performed a combustion analyzer test that checks for CO, CO2 and oxygen levels and the boiler was running great!
Nashua, NH 03062
Had to replace flapper
Had to replace flapper
Mark D.
Mark D. Checked in
Had to replace flapper
Bedford, NH 03110
I completed the oil boiler maintenance today. I replaced the oil filter, the pump strainer, and the nozzle. I pulled the front cover off the heat exchanger and brushed and vacuumed out the heat exchanger. I started up the boiler and performed a smoke test and there was zero smoke. I performed a combustion analyzer test that checks for CO, CO2 and oxygen levels and the boiler was running great.
I completed the oil boiler maintenance today. I replaced the oil filter, the pump strainer, and the nozzle. I pulled the front cover off the heat exchanger and brushed and vacuumed out the heat exchanger. I started up the boiler and performed a smoke test and there was zero smoke. I performed a combustion analyzer test that checks for CO, CO2 and oxygen levels and the boiler was running great.
Qwentin G.
Qwentin G. Checked in
I completed the oil boiler maintenance today. I replaced the oil filter, the pump strainer, and the nozzle. I pulled the front cover off the heat exchanger and brushed and vacuumed out the heat exchanger. I started up the boiler and performed a smoke test and there was zero smoke. I performed a combustion analyzer test that checks for CO, CO2 and oxygen levels and the boiler was running great.
Manchester, NH 03103
Mark D.
Mark D. Checked in
Had 104. Volts at furnace traced wires back to panel and found loose neutral wire.Stripped wire and reinstalled on neutral bar
Manchester, NH 03104
I completed the gas boiler maintenance today. I found that all three high vents were leaking. The temperature and pressure gauge failed. The fill valve and backflow preventer failed. The boiler relief valve was leaking. I replaced all those parts. For the maintenance I pulled the burner tubes and I cleaned them. I checked all the wiring connections and that all looked good. I checked incoming and outgoing gas pressures and those were according to manufacturer specifications. Lastly, I performed a combustion analyzer test that checks the CO, CO2 and oxygen levels and the boiler was running great. Both zones were coming back hot as well. I didn’t get to complete the other boiler maintenance for upstairs, but by the looks of it the expansion tank has failed. The relief valve has been dripping a little bit and the high vents might need to be replaced.
I completed the gas boiler maintenance today. I found that all three high vents were leaking. The temperature and pressure gauge failed. The fill valve and backflow preventer failed. The boiler relief valve was leaking. I replaced all those parts. For the maintenance I pulled the burner tubes and I cleaned them. I checked all the wiring connections and that all looked good. I checked incoming and outgoing gas pressures and those were according to manufacturer specifications. Lastly, I performed a combustion analyzer test that checks the CO, CO2 and oxygen levels and the boiler was running great. Both zones were coming back hot as well. I didn’t get to complete the other boiler maintenance for upstairs, but by the looks of it the expansion tank has failed. The relief valve has been dripping a little bit and the high vents might need to be replaced.
Jack D.
Jack D. Checked in
I completed the gas boiler maintenance today. I found that all three high vents were leaking. The temperature and pressure gauge failed. The fill valve and backflow preventer failed. The boiler relief valve was leaking. I replaced all those parts. For the maintenance I pulled the burner tubes and I cleaned them. I checked all the wiring connections and that all looked good. I checked incoming and outgoing gas pressures and those were according to manufacturer specifications. Lastly, I performed a combustion analyzer test that checks the CO, CO2 and oxygen levels and the boiler was running great. Both zones were coming back hot as well. I didn’t get to complete the other boiler maintenance for upstairs, but by the looks of it the expansion tank has failed. The relief valve has been dripping a little bit and the high vents might need to be replaced.
Nashua, NH 03060
Jack D.
Jack D. Checked in
Annual GSMS HomeClub PM on Viessmann boiler. Everything was gone through and your boiler is in great condition. Ready for another winter of dependable heat! I also flushed the water heater tank and removed/ inspected anode rod! All set. Thank you!
Concord, NH 03301
Goffstown, NH - Adjust toilet flapper to max setting. The flush did improve some. If it still isn't strong enough I'd reccomend replacing the existing toilet with a new one that has a stronger flush.
Jack D.
Jack D. Checked in
Adjust toilet flapper to max setting. The flush did improve some. If it still isn't strong enough I'd reccomend replacing the existing toilet with a new one that has a stronger flush.
Goffstown, NH 03045
I completed the oil boiler maintenance today. I replaced the oil filter, the pump strainer, the nozzle and the electrodes. We pulled the top off of the boiler and brushed and vacuumed out the heat exchanger. After running the boiler, I checked for smoke and there was 0 smoke. I performed a combustion analyzer test that checks for CO, CO2 and oxygen levels and the boiler was running great.
I completed the oil boiler maintenance today. I replaced the oil filter, the pump strainer, the nozzle and the electrodes. We pulled the top off of the boiler and brushed and vacuumed out the heat exchanger. After running the boiler, I checked for smoke and there was 0 smoke. I performed a combustion analyzer test that checks for CO, CO2 and oxygen levels and the boiler was running great.
Qwentin G.
Qwentin G. Checked in
I completed the oil boiler maintenance today. I replaced the oil filter, the pump strainer, the nozzle and the electrodes. We pulled the top off of the boiler and brushed and vacuumed out the heat exchanger. After running the boiler, I checked for smoke and there was 0 smoke. I performed a combustion analyzer test that checks for CO, CO2 and oxygen levels and the boiler was running great.
Candia, NH 03034
Review
Excellent service!
Darlene - Manchester, NH 03109
Jack D.
Jack D. Checked in
Cut out section of corroded 1/2" copper piping and replace with new section of pipe, new shut-off valve, and new fittings.
Manchester, NH 03109
Review
Very happy with the service. Technician was great!!!!
Susan - Hooksett, NH 03106
Review
Jack was awesome! Showed up for an emergency on a Sunday and was able to remedy the situation in no time! He took the time to explain everything throughout the process and was very thorough and efficient!
Chris - Barrington, NH 03825
Review
Completed job in a timely fashion attention to detail would hire again
Edward - Goffstown, NH 03045
Review
👍
Guimont - Manchester, NH 03103
Review
Home club member. Always great customer service from scheduling staff to HVAC technicians. Today, received maintenance furnace service from Qwentin Gauvin. Trustworthy, genuine and service oriented technician. Appreciate his efforts.
Manchester residential customer - Manchester, NH 03104
Review
Excellent service!
Travis - Concord, NH 03301
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
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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