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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 360 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

Madbury, NH - Completed the plumbing maintenance today. I started off with draining the indirect water tank. I labeled a few emergency shut off valves and showed the client where they were. I inspected the fixtures and drains and everything looked great. The client would like to have his gas line fixed behind his stove. The gas valve hits the stove so the stove can't sit flush with the wall. He said when we come out in the summertime to do the mini split maintenance would be a good time to do the repair.
Qwentin G.
Qwentin G. Checked in
Completed the plumbing maintenance today. I started off with draining the indirect water tank. I labeled a few emergency shut off valves and showed the client where they were. I inspected the fixtures and drains and everything looked great. The client would like to have his gas line fixed behind his stove. The gas valve hits the stove so the stove can't sit flush with the wall. He said when we come out in the summertime to do the mini split maintenance would be a good time to do the repair.
Madbury, NH 03823
Manchester, NH - Completed the Rinnai tankless water heater maintenance today. I started off with running cleaner through it for 35 minutes. After that I flushed 10 gallons of water through it. I cleaned the water inlet screen. I vacuumed out the inside of the unit. I checked incoming gas pressure and that was according to manufacturer specifications. The maintenance went great today.
Qwentin G.
Qwentin G. Checked in
Completed the Rinnai tankless water heater maintenance today. I started off with running cleaner through it for 35 minutes. After that I flushed 10 gallons of water through it. I cleaned the water inlet screen. I vacuumed out the inside of the unit. I checked incoming gas pressure and that was according to manufacturer specifications. The maintenance went great today.
Manchester, NH 03104
Jack D.
Jack D. Checked in
GSMS HomeClub plumbing visit!
Amherst, NH 03031
Manchester, NH - Replaced failed expansion tank and leaking pressure relief valve. Checked for leaks after and there were none. Lastly I ran the hot water and bled all the air out of the lines. The client has a old concrete slop sink in the basement and would like an estimate to remove it and replace it with a new one. The old sink drains directly into the floor.
Qwentin G.
Qwentin G. Checked in
Replaced failed expansion tank and leaking pressure relief valve. Checked for leaks after and there were none. Lastly I ran the hot water and bled all the air out of the lines. The client has a old concrete slop sink in the basement and would like an estimate to remove it and replace it with a new one. The old sink drains directly into the floor.
Manchester, NH 03102
Jack D.
Jack D. Checked in
Diagnose issue with bedroom being cold. I found dampers to be closed in basement. I opened them up.
Milford, NH 03055
Review
Quentin arrived in time, was courteous and professional and answered all my questions.
BJ - Merrimack, NH 03054
Adam P.
Adam P. Checked in
Install hose bib
Manchester, NH 03109
Completed the gas furnace maintenance today. I started off with checking all the electrical connections and everything looked good. I pulled the flame sensor and I cleaned it. The filter looks brand new. I checked incoming and outgoing gas pressures and those were according to manufacturer specifications. Lastly I ran the unit and performed a combustion analyzer test that checks the units CO, CO2 and oxygen levels and it was running great. The condensate pump has failed at some point so it is leaking water on the floor. There is no drain line either so we would have to figure out where to put that. The heat and the AC both produce water. Let us know if you would like that done and we would be happy to help. If you plan on using the AC in the summertime I would highly recommend doing a AC maintenance, we would come back out in the spring/summer time.
Completed the gas furnace maintenance today. I started off with checking all the electrical connections and everything looked good. I pulled the flame sensor and I cleaned it. The filter looks brand new. I checked incoming and outgoing gas pressures and those were according to manufacturer specifications. Lastly I ran the unit and performed a combustion analyzer test that checks the units CO, CO2 and oxygen levels and it was running great. The condensate pump has failed at some point so it is leaking water on the floor. There is no drain line either so we would have to figure out where to put that. The heat and the AC both produce water. Let us know if you would like that done and we would be happy to help. If you plan on using the AC in the summertime I would highly recommend doing a AC maintenance, we would come back out in the spring/summer time.
Mark D.
Mark D. Checked in
Completed the gas furnace maintenance today. I started off with checking all the electrical connections and everything looked good. I pulled the flame sensor and I cleaned it. The filter looks brand new. I checked incoming and outgoing gas pressures and those were according to manufacturer specifications. Lastly I ran the unit and performed a combustion analyzer test that checks the units CO, CO2 and oxygen levels and it was running great. The condensate pump has failed at some point so it is leaking water on the floor. There is no drain line either so we would have to figure out where to put that. The heat and the AC both produce water. Let us know if you would like that done and we would be happy to help. If you plan on using the AC in the summertime I would highly recommend doing a AC maintenance, we would come back out in the spring/summer time.
Pelham, NH 03076
Meet inspector. Fix cold shower. Start up furnace and do safety inspection.
Meet inspector. Fix cold shower. Start up furnace and do safety inspection.
Jack D.
Jack D. Checked in
Meet inspector. Fix cold shower. Start up furnace and do safety inspection.
Manchester, NH 03104
Heat exchanger has a blockage. Will need to replace as well as with the LP conversion kit. The low pressure switch does not appear to be installed, so we will need to install a new LP conversion kit with the low pressure switch. The heat exchanger will be covered under Lennox warranty, however it is understood that should Lennox request an inspection of the heat exchanger, there is a chance the warranty may be denied due to the pressure switch never being installed. Based on the venting, we will need to replace the concentric vent kit with Lennox Accelerator-style venting. The venting will also be adjusted to terminate out the bay over to provide proper separation from the Rinnai vent.
Heat exchanger has a blockage. Will need to replace as well as with the LP conversion kit. The low pressure switch does not appear to be installed, so we will need to install a new LP conversion kit with the low pressure switch. The heat exchanger will be covered under Lennox warranty, however it is understood that should Lennox request an inspection of the heat exchanger, there is a chance the warranty may be denied due to the pressure switch never being installed. Based on the venting, we will need to replace the concentric vent kit with Lennox Accelerator-style venting. The venting will also be adjusted to terminate out the bay over to provide proper separation from the Rinnai vent.
Adam P.
Adam P. Checked in
Heat exchanger has a blockage. Will need to replace as well as with the LP conversion kit. The low pressure switch does not appear to be installed, so we will need to install a new LP conversion kit with the low pressure switch. The heat exchanger will be covered under Lennox warranty, however it is understood that should Lennox request an inspection of the heat exchanger, there is a chance the warranty may be denied due to the pressure switch never being installed. Based on the venting, we will need to replace the concentric vent kit with Lennox Accelerator-style venting. The venting will also be adjusted to terminate out the bay over to provide proper separation from the Rinnai vent.
Hopkinton, NH 03229
Replace valve and supply and install toilet
Replace valve and supply and install toilet
Mark D.
Mark D. Checked in
Replace valve and supply and install toilet
Pelham, NH 03076
Review
Excellent and professional work , all great
Alison - Bedford, NH 03110
Review
Qwentin is awesome, very knowledgeable and an overall good guy
James - Manchester, NH 03104
Review
Excellent!!!
Kathleen - Merrimack, NH 03054
Review
When a GSMS contractor comes to your home, it’s not just another contractor doing a job, it’s a personable experience from someone who truly cares about the neatness and quality of their work to the quality of their relationship with you, the customer… they quickly feel like an extension of your family making you look forward to their visits and not feeling concerned in any way how it’s going to go. Always 5 stars from me and two thumbs up, if I can count my big toes, it’s 4 digits up from me!! 👍👍👍👍🙂🙂
Martin - Stratham, NH 03885
Review
Great work as always
Mark - Hollis, NH 03049
Review
Jack did a super job! Very thorough and competent. I feel like I’m in good hands with GSMS.
BJ - Merrimack, NH 03054
Review
Friendly and transparent. Explained all aspects of the service.
Jeffrey - Nashua, NH 03064
Review
Qwentin is a pleasure to have work at our house. He is friendly, informative, and clearly knows what he is doing.
Barry - Manchester, NH 03109
Review
We had an issue with our furnace and called GSMS on recommendation from a friend. I called and spoke with Gina to schedule an appointment. (She is very pleasant with a great attitude!) A service specialist, named Qwentin, came out to assess the issue. Qwen is great! He spoke well and is quite knowledgeable. He explained the issue, proposed a solution and a provided quote to fix. Although he didn’t have the part, he indicated he would quickly leave, go get the part and come right back to install—- all in that same visit! Qwentin‘s customer service skills, along with everyone else I’ve spoken with at GSMS, are top-notch. Going forward, we will use GSMS for our Plumbing, Air, Heating needs.
Liz - 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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