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Our Service Area

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 340 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
Snake out the bathroom sink and bathroom tub drain due to continued clogging. Remove piping in wall to access sink drain piping due to snake not being able to make the turn. The TEE was blocked and is now freed up. The blockage is now cleared up. Tested for leaks and all set. Thank you!
Litchfield, NH 03052
Review
Excellent work
Turning - Manchester, NH 03103
Completed the system 2000 gas boiler maintenance today. I started off with checking all the wiring connections and everything looked good. I checked all the boiler accessories and everything looked good. I pulled out the flame sensor and electrode setup and I cleaned it. I checked incoming and outgoing gas pressures and those were according to manufacturer's specifications. I performed a combustion analyzer test that checks the units CO, CO2, oxygen levels and draft. I had to adjust the air setting a tad bit. The client had to replace the draft inducer about 2 years ago because of corrosive build up on the gasket. I found out through tech support that water is making it's way back to the inducer so we should add in a drain line to prevent this. I will send over the estimate next week for the drain line.
Completed the system 2000 gas boiler maintenance today. I started off with checking all the wiring connections and everything looked good. I checked all the boiler accessories and everything looked good. I pulled out the flame sensor and electrode setup and I cleaned it. I checked incoming and outgoing gas pressures and those were according to manufacturer's specifications. I performed a combustion analyzer test that checks the units CO, CO2, oxygen levels and draft. I had to adjust the air setting a tad bit. The client had to replace the draft inducer about 2 years ago because of corrosive build up on the gasket. I found out through tech support that water is making it's way back to the inducer so we should add in a drain line to prevent this. I will send over the estimate next week for the drain line.
Qwentin G.
Qwentin G. Checked in
Completed the system 2000 gas boiler maintenance today. I started off with checking all the wiring connections and everything looked good. I checked all the boiler accessories and everything looked good. I pulled out the flame sensor and electrode setup and I cleaned it. I checked incoming and outgoing gas pressures and those were according to manufacturer's specifications. I performed a combustion analyzer test that checks the units CO, CO2, oxygen levels and draft. I had to adjust the air setting a tad bit. The client had to replace the draft inducer about 2 years ago because of corrosive build up on the gasket. I found out through tech support that water is making it's way back to the inducer so we should add in a drain line to prevent this. I will send over the estimate next week for the drain line.
Hudson, NH 03051
Windham, NH - Completed the plumbing walkthrough of the house. I checked all the fixtures and drains and the only thing that I noticed was the kitchen sink trap nut was a little bit loose so it's been dripping water. After tightening it, it wasn't dripping anymore. I completed the maintenance on the rinnai. I ran cleaner through it for about 40 minutes. I flushed it after with 10 gallons of water. I cleaned the supply water inlet screen. I vacuumed out the inside of the unit. I checked incoming gas pressure and that was according to manufacturer specifications. Everything went good today.
Qwentin G.
Qwentin G. Checked in
Completed the plumbing walkthrough of the house. I checked all the fixtures and drains and the only thing that I noticed was the kitchen sink trap nut was a little bit loose so it's been dripping water. After tightening it, it wasn't dripping anymore. I completed the maintenance on the rinnai. I ran cleaner through it for about 40 minutes. I flushed it after with 10 gallons of water. I cleaned the supply water inlet screen. I vacuumed out the inside of the unit. I checked incoming gas pressure and that was according to manufacturer specifications. Everything went good today.
Windham, NH 03087
I started off with completing the whole house plumbing inspection. All the fixtures and drains looked good and there we're no leaks. I cleaned out the filter for the air derator in the master bedroom. Next I completed the rinnai maintenance. I ran cleaner for about 40 minutes. After I flushed around 10 gallons of water through it. I cleaned the cold water inlet screen. I noticed on the hot water outlet there was a lot of rust and is starting to rot out the bottom of the hot water heater. I also noticed that the pressure relief valve has been dripping. I will send over an estimate to fix the leaking connection inside of the water heater and to replace the pressure relief valve. One thing I wanted to mention that I noticed with my plumbing inspection was that the bypass valve for the water treatment is opened when it is normally shut. I'm not sure if that was done on purpose by your water treatment company but I wanted to make aware.
I started off with completing the whole house plumbing inspection. All the fixtures and drains looked good and there we're no leaks. I cleaned out the filter for the air derator in the master bedroom. Next I completed the rinnai maintenance. I ran cleaner for about 40 minutes. After I flushed around 10 gallons of water through it. I cleaned the cold water inlet screen. I noticed on the hot water outlet there was a lot of rust and is starting to rot out the bottom of the hot water heater. I also noticed that the pressure relief valve has been dripping. I will send over an estimate to fix the leaking connection inside of the water heater and to replace the pressure relief valve. One thing I wanted to mention that I noticed with my plumbing inspection was that the bypass valve for the water treatment is opened when it is normally shut. I'm not sure if that was done on purpose by your water treatment company but I wanted to make aware.
Qwentin G.
Qwentin G. Checked in
I started off with completing the whole house plumbing inspection. All the fixtures and drains looked good and there we're no leaks. I cleaned out the filter for the air derator in the master bedroom. Next I completed the rinnai maintenance. I ran cleaner for about 40 minutes. After I flushed around 10 gallons of water through it. I cleaned the cold water inlet screen. I noticed on the hot water outlet there was a lot of rust and is starting to rot out the bottom of the hot water heater. I also noticed that the pressure relief valve has been dripping. I will send over an estimate to fix the leaking connection inside of the water heater and to replace the pressure relief valve. One thing I wanted to mention that I noticed with my plumbing inspection was that the bypass valve for the water treatment is opened when it is normally shut. I'm not sure if that was done on purpose by your water treatment company but I wanted to make aware.
Windham, NH 03087
Zak D.
Zak D. Checked in
Next I completed the gas steam boiler maintenance for the Burnham boiler. I started off with checking all the electrical connections and everything looked good. I pulled the burner tubes and I cleaned them. I vacuumed out the burner box. I cleaned the flame sensor. I checked incoming and outgoing gas pressures and those were according to manufacturer specifications. Next I drain down the boiler. I removed the pigtail to clean it out but it was so plugged up with sediment that I wasn't able to clean it. I replaced it with a new one. I went to pull out the low water cutoff probe and everything I tried I could not get it out and I was worried about snapping it. I tested the low water cut off and it worked as it should. The automatic water feed worked as well. Lastly I ran the boiler and performed a combustion analyzer test that checks the units CO, CO2 and oxygen levels. The boiler was running good.
Manchester, NH 03102
Replacement of the existing heating and cooling system with a new high-efficiency Lennox system.

The new system will maintain the same footprint, utilizing the existing poured concrete pad outside and the existing location for the furnace inside. The new furnace venting will feature a two-pipe design on the exterior instead of the existing concentric one-pipe design. The existing bypass humidifier will be reconnected to the new system, and a new right-angle AirBear unit will be installed for enhanced air filtration.

For improved performance, the existing zone dampers will be replaced with new dampers as part of installing our new Lennox Smart Zoning System. This system allows the heating and cooling unit to precisely control the zoning, only delivering the exact amount of energy needed per zone. This approach maximizes efficiency and increases comfort by delivering the exact airflow needed for quiet operation. Our Lennox Smart Zoning uses our Lennox smart thermostats, which offer a u
Replacement of the existing heating and cooling system with a new high-efficiency Lennox system.

The new system will maintain the same footprint, utilizing the existing poured concrete pad outside and the existing location for the furnace inside. The new furnace venting will feature a two-pipe design on the exterior instead of the existing concentric one-pipe design. The existing bypass humidifier will be reconnected to the new system, and a new right-angle AirBear unit will be installed for enhanced air filtration.

For improved performance, the existing zone dampers will be replaced with new dampers as part of installing our new Lennox Smart Zoning System. This system allows the heating and cooling unit to precisely control the zoning, only delivering the exact amount of energy needed per zone. This approach maximizes efficiency and increases comfort by delivering the exact airflow needed for quiet operation. Our Lennox Smart Zoning uses our Lennox smart thermostats, which offer a u
Adam P.
Adam P. Checked in
Replacement of the existing heating and cooling system with a new high-efficiency Lennox system. The new system will maintain the same footprint, utilizing the existing poured concrete pad outside and the existing location for the furnace inside. The new furnace venting will feature a two-pipe design on the exterior instead of the existing concentric one-pipe design. The existing bypass humidifier will be reconnected to the new system, and a new right-angle AirBear unit will be installed for enhanced air filtration. For improved performance, the existing zone dampers will be replaced with new dampers as part of installing our new Lennox Smart Zoning System. This system allows the heating and cooling unit to precisely control the zoning, only delivering the exact amount of energy needed per zone. This approach maximizes efficiency and increases comfort by delivering the exact airflow needed for quiet operation. Our Lennox Smart Zoning uses our Lennox smart thermostats, which offer a u
Auburn, NH 03032
Review
Great service!
Colleen - Manchester, NH 03104
Downstairs bathroom sink trap has a very small leak when water is ran. I added a emergency shut off tag to water meter and oil tank. All other plumbing looked great in the house.
Downstairs bathroom sink trap has a very small leak when water is ran. I added a emergency shut off tag to water meter and oil tank. All other plumbing looked great in the house.
Qwentin G.
Qwentin G. Checked in
Downstairs bathroom sink trap has a very small leak when water is ran. I added a emergency shut off tag to water meter and oil tank. All other plumbing looked great in the house.
Manchester, NH 03104
Found that the furnace exhaust pipe was condensing and water was running down the pipe and getting inside of the house. This is due to too much piping outside that is uninsulated. Client approved the estimate to properly revent the intake and exhaust pipes.
Found that the furnace exhaust pipe was condensing and water was running down the pipe and getting inside of the house. This is due to too much piping outside that is uninsulated. Client approved the estimate to properly revent the intake and exhaust pipes.
Qwentin G.
Qwentin G. Checked in
Found that the furnace exhaust pipe was condensing and water was running down the pipe and getting inside of the house. This is due to too much piping outside that is uninsulated. Client approved the estimate to properly revent the intake and exhaust pipes.
Raymond, NH 03077
Jack D.
Jack D. Checked in
Boiler repairs.
Concord, NH 03301
Completed the gas steam boiler maintenance today. I started off with checking all the wiring connections and everything was good. Next I pulled out the burner tubes and I cleaned them. I vacuumed the inside of the burner box. I cleaned the flame sensor. I checked incoming and outgoing gas pressures and everything was according to manufacturer specifications. I drained down all of the water in the boiler. I found that the low water cut off wasn't sensing that there wasn't any water in the boiler. When I pulled the probe out to clean it, it was extremely dirty so it wasn't able to sense that the water level was low. I found that there was no water in the sight glass. The valves had been shut and the ports were extremely blocked up. I found that the top of the sight glass had been broken, I'm assuming that's why the valves were shut. I pulled the pigtail off of the boiler and that was extremely plugged up as well. I brushed it out and cleaned it out with water. Next I replaced the sight g
Completed the gas steam boiler maintenance today. I started off with checking all the wiring connections and everything was good. Next I pulled out the burner tubes and I cleaned them. I vacuumed the inside of the burner box. I cleaned the flame sensor. I checked incoming and outgoing gas pressures and everything was according to manufacturer specifications. I drained down all of the water in the boiler. I found that the low water cut off wasn't sensing that there wasn't any water in the boiler. When I pulled the probe out to clean it, it was extremely dirty so it wasn't able to sense that the water level was low. I found that there was no water in the sight glass. The valves had been shut and the ports were extremely blocked up. I found that the top of the sight glass had been broken, I'm assuming that's why the valves were shut. I pulled the pigtail off of the boiler and that was extremely plugged up as well. I brushed it out and cleaned it out with water. Next I replaced the sight g
Qwentin G.
Qwentin G. Checked in
Completed the gas steam boiler maintenance today. I started off with checking all the wiring connections and everything was good. Next I pulled out the burner tubes and I cleaned them. I vacuumed the inside of the burner box. I cleaned the flame sensor. I checked incoming and outgoing gas pressures and everything was according to manufacturer specifications. I drained down all of the water in the boiler. I found that the low water cut off wasn't sensing that there wasn't any water in the boiler. When I pulled the probe out to clean it, it was extremely dirty so it wasn't able to sense that the water level was low. I found that there was no water in the sight glass. The valves had been shut and the ports were extremely blocked up. I found that the top of the sight glass had been broken, I'm assuming that's why the valves were shut. I pulled the pigtail off of the boiler and that was extremely plugged up as well. I brushed it out and cleaned it out with water. Next I replaced the sight g
Manchester, NH 03102
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
The experience started with Gina in the office who was very responsive and accommodating and made the scheduling process super efficient and friendly. Then Mark came and brought his expertise to my home and systems to point areas of installation failures by the company that installed my system. Just using the basic manual to point out how they cut corners. Mark spent the time to correct the exhaust piping to fix leaks and improve air flow. He was friendly and accommodating.
Nelson - Merrimack, NH 03054
Review
Whenever Mark is on the way, you know it’s gonna be fixed correctly. He is awesome!
Kathleen - Nashua, NH 03064
Review
Mark is always very professional and clearly communicates all options. He and his team are able to accommodate us and get the job done in a timely manner. THANK YOU!
Joyce - Hudson, NH 03051
Review
Arrived on time. Work was completed timely. Cleaned up afterwards. Very pleased with the service.
Charlie - New Boston, NH 03070
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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