Proudly serving New Hampshire homeowners with local heating, air & plumbing services.
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.
From air conditioning and heating services to plumbing repairs and installations, we ensure your home remains comfortable and efficient year-round. Our commitment to quality and customer satisfaction sets us apart as the trusted choice for all your home comfort needs.
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
Customers say: The reviews exhibit a positive sentiment towards Granite State Mechanical Services (GSMS). The majority of the reviews are positive, highlighting the quality of service, professionalism, and expertise of the staff. Customers appreciate the prompt and efficient service, with many expressing satisfaction with the work done. Positive reviews mention the friendly and knowledgeable technicians, the cleanliness of the installation, and the reasonable prices. Customers also emphasize the trustworthiness and reliability of GSMS, stating that they are the only plumber they will ever need. The positive reviews often mention specific individuals, such as Jack, Mark, and Quentin, who are praised for their knowledge, courtesy, and quality of work. However, there are a few negative reviews, which mainly focus on issues related to scheduling or communication. Customers express frustration with delays or unfulfilled promises, but these negative reviews are outweighed by the positive ones. Overall, the sentiment of the reviews is positive, with customers expressing satisfaction with the services provided by GSMS.
Job Locations and Reviews

Replacement of existing system with a new GSMS system to provide cooling to the home. Refrigerant line set replaced completely - hole through foundation will be sealed up with cement patch and new penetration made through sill plate. New Ecobee wifi thermostat installed for the first floor zone to provide control of the system zone from wifi/app. Other zone will be replaced with a standard programmable thermostat similar to existing setup. New zoning module with two zone dampers will be installed for efficient system performance. Existing poured concrete pad will be re-used for new condensing unit. Floor drain condensate pump will be removed and replaced with a standard condensate pump that will pump into the washing machine drain.

Tune up Lennox oil furnace

Replaced garbage disposal

Relocate intake next to exhaust change to 2"

Pull and reset leaking toilet. Custom end caps.

Installation of a high-efficiency heat pump system to provide reliable and efficient cooling and supplemental heating to the home. Based on the load requirements and using the system for primary cooling and supplemental heating, we can design a single outdoor unit design. Existing electrical panels are code-approved with 200A service from the street. We will install a dedicated circuit which will serve each system.

Replaced outside faucet

Replaced toilet and install outside faucet

I called Rinnai tech-support when I got to the clients house. We ran through a couple tests while we had the hot water on and we were not able to recreate the problem it was having. We did find there to be a stored error code, code 10, which possibly indicates that the burners are dirty. I talked to the client and we are going to go through with cleaning the burners out.
Always very responsive to issues and both furnace issues resolved quickly

Checked plumbing no issues
Excellent service, very professional, and very helpful
Quality work, great follow up and excellent communication with a reasonable price!
Excellent service!
Mark is careful, knowledgable, efficient, and friendly Thanks!
High recommend. Called GSMS because of a leak. Jack arrive and within minutes diagnosed the problem - and fixed it. Thank you
Great service
Thank you for the great service!!
Jack is the best. He goes out of his way to make sure we are taken care of and have what we need. He’s great
Thank you for taking the time to leave such a positive review! We're glad to hear you had a great experience with Jack.
Jack is always very knowledgeable and kind and helpful when servicing our home. Thank you!
We're thrilled to hear that you enjoyed your experience with us. Thanks for the kind words!
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Derry NH -
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Henniker, NH -
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Weare, NH -
Windham, NH