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 provided content describes the overall sentiment of the reviews as positive. The reviewers consistently express satisfaction with the services provided by Granite State Mechanical Services (GSMS). They mention factors such as responsiveness, dependability, fair pricing, thoroughness, cleanliness, use of technology, and the quality of the work. Positive reviews highlight the friendliness, expertise, efficiency, and reliability of the technicians, as well as their integrity, honesty, and performance. Customers appreciate the prompt and effective resolution of issues, the professionalism, and the trust they have in the GSMS team. The positive reviews also mention the range of services offered, including plumbing, HVAC, and air quality testing, as well as the positive experiences with scheduling, communication, and the overall customer service. Overall, the sentiment expressed in the reviews is overwhelmingly positive, with customers expressing high levels of satisfaction and recommending GSMS to others.
Job Locations and Reviews

Hookup gas stove. New flexible connector. Check for leaks with electronic detector and bubble spray. Fabricated and installed anti-tip brackets for the oven. Pull and reset toilet that was leaking around base.

Snake shower drain. Remove bathroom sink pop up and clean. Run drain cleaner down both drains. Replace master bathroom faucet. Replace master bathroom sink drain trap because the old one was cracked and dripping. Test thoroughly for leaks.

I started off with vacuuming the inside of the unit. I checked all the wiring connections and everything looked great. I cleaned and flushed the trap with cleaner. The air filter is a 12 month replacement filter and looked really clean so I left it in the system. I went outside and I washed the outdoor unit with water and coil cleaner. I checked electrical connections and everything looked good. Lastly, I ran the unit in heat mode and checked the pressures. Everything was working as it should.

I found out that the zone dampener was being opened to the second floor when the first floor was calling for heat. The thermostat wires going through the wall to the upstairs thermostat were shorting out to each other creating a call when the first floor would turn on. I talked to the client and the only way to solve that is to use a Wireless thermostat. The client wanted to update all three of his thermostats as well. I performed a maintenance on both Lennox and Mitsubishi mini splits. I started with cleaning them both from the inside out with water. I cleaned the outside of the unit as well. Everything looked great. Inside I washed the air filters with Dawn soap and water. I cleaned the indoor coils as well with Dawn soap and water. All the mini splits were in very good condition.

Estimate for gasline to grill

I found that the first and second floor systems both have leaks. I also found that the Bosch heat pump had a cover over the top of it so I removed it. I talked to the owner about everything that I found and he would like us to come back in mid May to recharge the first and maybe second floor system. He also wanted an estimate to replace the whole second floor system. Also, when we come back in May, he wanted the first maintenance done on the Bosch heat pump unit.

New waste&overflow,tub&shower valve and finish work
Excellent Service!
Excellent Service!

Replace main board, driver board, compressor thermistor, and eev. Also repair damaged wires.

Pump refrigerant down into unit, disconnect piping, mount wall stand, mount unit, reconfigure and connect piping, pressure test, pull vacuum on system, open lines back up, operate unit to verify no problems. Repeat same process on other system.

I started off with checking all electrical connections inside and everything looked good. The client replaces his own filters. I cleaned the trap and condensate pump with cleaner. Next I went outside and washed the outdoor unit with water and then soap. I checked the electrical connections outside and everything looked perfect. Lastly I checked the operating pressures in heating mode since it wasn’t warm enough to do it in air conditioning mode. The pressures looked good.
We have used GSMS for over twenty years and have found them to be highly responsive, dependable, fairly priced, and thorough. They always keep my home clean, wearing covers over their work boots. Their use of technology to track arrival time is very helpful. We recommend them highly.
Jack is friendly down to earth guy who knows his stuff. He reviewed my problem and has a smart solution to fix it. His work is top notch and reasonable!
GSMS air air quality experts, they have all of the right tools to test and create a safe air environment in our home. Fast reasonable friendly service with a smile!
A plus job ! Would recommend to others
Your GSMS team set the standard in your business area for integrity, honesty, performance and quality. They are courteous and we trust them being in our home.
Jack is very personable. Happy with the work done.
Excellent service
Mark and his family run a top tier heating and plumbing business. I would not go anywhere else. I have three houses and they take care of everything.
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Windham, NH