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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 379 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
Installed. New water lines&jack installed new heater.Jack will finish heater tomorrow and install toilet.I need to go back to install plumbing and pump to new sink.Also Eric wants hot and cold outside faucet
Exeter, NH 03833
Repair piping in closet that rodents chewed. Replace 2 valves under sink. We will quote to repair main shutoff valve and replace the hot and cold manifolds.
Repair piping in closet that rodents chewed. Replace 2 valves under sink. We will quote to repair main shutoff valve and replace the hot and cold manifolds.
Jack D.
Jack D. Checked in
Repair piping in closet that rodents chewed. Replace 2 valves under sink. We will quote to repair main shutoff valve and replace the hot and cold manifolds.
Derry, NH 03038
Completed the maintenance on the gas boiler. Started off with checking electrical connections and everything looked good. I vacuumed out the burner box and the burner tubes. I checked all the boiler accessories and I found that the pressure relief valve was leaking and the high vent was leaking water. I checked incoming and outgoing gas pressures and those were according to manufacturer specifications. Lastly I ran the boiler and performed a combustion analyzer test. This checks the unit CO, CO2 and oxygen levels. The boiler was running good. I will send over an estimate for those repairs. This unit is from 1978.
Completed the maintenance on the gas boiler. Started off with checking electrical connections and everything looked good. I vacuumed out the burner box and the burner tubes. I checked all the boiler accessories and I found that the pressure relief valve was leaking and the high vent was leaking water. I checked incoming and outgoing gas pressures and those were according to manufacturer specifications. Lastly I ran the boiler and performed a combustion analyzer test. This checks the unit CO, CO2 and oxygen levels. The boiler was running good. I will send over an estimate for those repairs. This unit is from 1978.
Qwentin G.
Qwentin G. Checked in
Completed the maintenance on the gas boiler. Started off with checking electrical connections and everything looked good. I vacuumed out the burner box and the burner tubes. I checked all the boiler accessories and I found that the pressure relief valve was leaking and the high vent was leaking water. I checked incoming and outgoing gas pressures and those were according to manufacturer specifications. Lastly I ran the boiler and performed a combustion analyzer test. This checks the unit CO, CO2 and oxygen levels. The boiler was running good. I will send over an estimate for those repairs. This unit is from 1978.
Manchester, NH 03103
Review
Qwentin did a great job. Highly recommend him.
Gary - Stratham, NH 03885
Review
Excellent, prompt service
John - Hollis, NH 03049
Completed the boiler maintenance today. I started off with checking the wiring connections and everything looked good. I vacuumed out the burner box and the burner tubes. I checked all the boiler accessories and everything looked good. The only thing I notice was that the circulator pump is leaking water from the flange so I will send over an estimate to replace that. I checked incoming and outgoing gas pressures and those were according to manufacturer specifications. Lastly I ran the boiler and performed a combustion analyzer test that checks the unit CO, CO2 and oxygen levels. The boiler was running good. The boiler is from 1975-1977.
Completed the boiler maintenance today. I started off with checking the wiring connections and everything looked good. I vacuumed out the burner box and the burner tubes. I checked all the boiler accessories and everything looked good. The only thing I notice was that the circulator pump is leaking water from the flange so I will send over an estimate to replace that. I checked incoming and outgoing gas pressures and those were according to manufacturer specifications. Lastly I ran the boiler and performed a combustion analyzer test that checks the unit CO, CO2 and oxygen levels. The boiler was running good. The boiler is from 1975-1977.
Qwentin G.
Qwentin G. Checked in
Completed the boiler maintenance today. I started off with checking the wiring connections and everything looked good. I vacuumed out the burner box and the burner tubes. I checked all the boiler accessories and everything looked good. The only thing I notice was that the circulator pump is leaking water from the flange so I will send over an estimate to replace that. I checked incoming and outgoing gas pressures and those were according to manufacturer specifications. Lastly I ran the boiler and performed a combustion analyzer test that checks the unit CO, CO2 and oxygen levels. The boiler was running good. The boiler is from 1975-1977.
Manchester, NH 03103
Qwentin G.
Qwentin G. Checked in
N/A
Manchester, NH 03103
Project Overview

Supply and install a multi-zone ductless heat pump system to serve both the Master Bedroom and the first-floor Family Room. This solution allows for independent temperature control in each space, providing high-efficiency cooling, dehumidification, and supplemental heating.

Scope of Work

1. Equipment Installation

Master Bedroom (Indoor Unit A): Install one (1) High-Wall Indoor Unit, positioned on the wall facing the backyard.

Family Room (Indoor Unit B): Install one (1) High-Wall Indoor Unit in the location of the existing in-wall A/C.

Outdoor Unit: Position the outdoor condenser on the ground level underneath the bay window.

Client Responsibilities: * Shrub Relocation: Client will need to relocate one shrub to provide clearance for the outdoor unit.

Carpentry: Client to have their carpenter remove the existing in-wall A/C unit and patch/finish the wall opening prior to our installation so the new indoor unit can be mounted seamlessly over that location.

2. Li
Project Overview

Supply and install a multi-zone ductless heat pump system to serve both the Master Bedroom and the first-floor Family Room. This solution allows for independent temperature control in each space, providing high-efficiency cooling, dehumidification, and supplemental heating.

Scope of Work

1. Equipment Installation

Master Bedroom (Indoor Unit A): Install one (1) High-Wall Indoor Unit, positioned on the wall facing the backyard.

Family Room (Indoor Unit B): Install one (1) High-Wall Indoor Unit in the location of the existing in-wall A/C.

Outdoor Unit: Position the outdoor condenser on the ground level underneath the bay window.

Client Responsibilities: * Shrub Relocation: Client will need to relocate one shrub to provide clearance for the outdoor unit.

Carpentry: Client to have their carpenter remove the existing in-wall A/C unit and patch/finish the wall opening prior to our installation so the new indoor unit can be mounted seamlessly over that location.

2. Li
Adam P.
Adam P. Checked in
Project Overview Supply and install a multi-zone ductless heat pump system to serve both the Master Bedroom and the first-floor Family Room. This solution allows for independent temperature control in each space, providing high-efficiency cooling, dehumidification, and supplemental heating. Scope of Work 1. Equipment Installation Master Bedroom (Indoor Unit A): Install one (1) High-Wall Indoor Unit, positioned on the wall facing the backyard. Family Room (Indoor Unit B): Install one (1) High-Wall Indoor Unit in the location of the existing in-wall A/C. Outdoor Unit: Position the outdoor condenser on the ground level underneath the bay window. Client Responsibilities: * Shrub Relocation: Client will need to relocate one shrub to provide clearance for the outdoor unit. Carpentry: Client to have their carpenter remove the existing in-wall A/C unit and patch/finish the wall opening prior to our installation so the new indoor unit can be mounted seamlessly over that location. 2. Li
Hollis, NH 03049
Qwentin G.
Qwentin G. Checked in
Replaced the faulty fan limit switch. Tested operation and got it set up correctly.
Stratham, NH 03885
Jack D.
Jack D. Checked in
I believe the burning smell was caused by loose insulation threads making contact with the hest exchanger. I removed the threads and the smell went away.
Nashua, NH 03062
Replaced the failed indirect water tank. Checked for leaks and there was none. Replaced the domestic water expansion tank. Completed the maintenance on the boiler. I started off with checking all the wiring connections and everything looked good. Next I pulled the flame sensor and cleaned it. I vacuumed out the burners and the burner box. I checked incoming and outgoing gas pressure and those were accordance to manufacturer specifications. I inspected all the boiler accessories and the only thing that I found was that the high vent was leaking water. Lastly I ran the unit and performed a combustion analyzer test. This checks the unit CO, CO2 and oxygen levels. The boiler was running good. I bled the air from the hot and cold water lines before I left.
Replaced the failed indirect water tank. Checked for leaks and there was none. Replaced the domestic water expansion tank. Completed the maintenance on the boiler. I started off with checking all the wiring connections and everything looked good. Next I pulled the flame sensor and cleaned it. I vacuumed out the burners and the burner box. I checked incoming and outgoing gas pressure and those were accordance to manufacturer specifications. I inspected all the boiler accessories and the only thing that I found was that the high vent was leaking water. Lastly I ran the unit and performed a combustion analyzer test. This checks the unit CO, CO2 and oxygen levels. The boiler was running good. I bled the air from the hot and cold water lines before I left.
Jack D.
Jack D. Checked in
Replaced the failed indirect water tank. Checked for leaks and there was none. Replaced the domestic water expansion tank. Completed the maintenance on the boiler. I started off with checking all the wiring connections and everything looked good. Next I pulled the flame sensor and cleaned it. I vacuumed out the burners and the burner box. I checked incoming and outgoing gas pressure and those were accordance to manufacturer specifications. I inspected all the boiler accessories and the only thing that I found was that the high vent was leaking water. Lastly I ran the unit and performed a combustion analyzer test. This checks the unit CO, CO2 and oxygen levels. The boiler was running good. I bled the air from the hot and cold water lines before I left.
Hooksett, NH 03106
Jack D.
Jack D. Checked in
Boiler flow switch is bad. I installed temporary low water cut off in order to keep the boiler on line for the residents. We will order the switch and return this week to replace it.
Concord, NH 03301
Review
It’s always a pleasure when Qwentin stops by; a polite and personable young man who is an asset to the formidable GSMS team who did another super, duper jobby! 😉 Hope he had a great time at the party celebrating multiple birthdays this weekend?! Cheers 👍🙂🥃🥃
Martin - Stratham, NH 03885
Review
Adam & Quinn just left after finishing the installation of my new Lennox Air Conditioning unit. As always, they are very personable and professional. Adam explains everything to me before he leaves and I am very comfortable with my new system. I would not hesitate to recommend GSMS and have done so in the past.
Deb - Hooksett, NH 03106
Review
Qwentin was thorough and diagnosed the issue
Gary - Stratham, NH 03885
Review
Great service
Lori B - Hollis, NH 03049
Review
Excellent Service
Ronald - Merrimack, NH 03054
Review
Excellent service and communication. A great family business.
Paul - Nashua, NH 03062
Review
Quentin gave me all the information I requested and was exceptionally polite and did a through job. I highly recommend him and GSMS company !
John - Weare, NH 03281
Review
We use GSMS for all our bathroom remodels! Mark, Jack and Zak have been awesome to work with.
Peggy - Granite State Home Improvements - Strafford, NH 03884
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
I needed to have shut off valves under my kitchen sink and a new hose attachment on my sprayer since the cheap plastic tubing was cracked. Mark was punctual, professional and extremely knowledgeable regarding the job. I am always impressed with GSM and how they run their family business. Mark completed the job quickly and efficiently. I can trust GSM and will continue to seek their help in the help in the future. GSM has installed a mini split, oil boiler, hot water heater in my home and I would highly recommend them to family and friends.
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.

Trusted Quality & Service