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
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
Scope of Work: Replacement of the existing oil-fired boiler with a new, reliable Cast Iron Oil Boiler featuring an internal tankless coil for domestic hot water. Hydronic Piping Upgrade (GSMS Standard): Circulator Conversion: We will remove the existing system of zone valves and a single pump. The system will be repiped to feature dedicated circulator pumps for each of the two heating zones. This upgrade provides better flow, redundancy, and reliability. Near-Boiler Piping: Installation includes our complete piping package: new isolation flanges, high-performance air eliminator, expansion tank, automatic feed valve, and backflow preventer. Domestic Hot Water: The new boiler will include an internal Tankless Coil to generate domestic hot water, maintaining the same style of operation as the current system. Venting & burner: A new high-efficiency oil burner will be set up and calibrated. The boiler will be connected to the existing chimney flue.
Preventative maintenance completed on your Ideal combi boiler. Everything went great. Please see the maintenance form for details of todays servicing. I was able to recreate the noise that you are experiencing. I sent a video to our manufacturer representative. We will contact you with a solution. Thank you!
The steam boilers automatic water feed seems to be acting up. We will order the new one today. We would also like to get access to all the apartments that the steam boiler heats. Regarding apartment #4 for not being heated I'm pretty sure that the pipes froze going to that apartment. If this problem continues to exist we will have to take a look at it further. We will be in touch with when we can come back out to replace the part.
Toilet repair and water test.
Completed the house plumbing inspection today. I checked all the drains and fixtures and everything looked great. I labeled a bunch of emergency shut offs and I showed the client where they were. I completed the rinnai tankless water heater maintenance. I ran cleaner for 35 minutes. After I flushed 10 gallons of water through it. I cleaned the water inlet screen and somehow wood got inside of it. I checked incoming gas pressure and that was according to manufacturer's specifications. I cleaned the electrode and flame sensors. Lastly I ran the unit and it was running great!
Remove and reassemble drain assembly. Reseal leaking connections and reconnect pop up. Thank you!
Adjust gas pressure.
I found that the downstairs humidifier wasn't working because the switch wasn't on. Upstairs I found that the humidifier control had no power going to it. Someone at some point had unwired the humidifier for some reason. We'll have to come back to rewire the humidifier. I also mention that we should do both of the furnace maintenances and she wanted that done as well.
Completed the whole house plumbing inspection. All the drains and fixtures looked good. Completed the tankless water heater maintenance. I ran cleaner through it for 35 minutes. After I flushed 10 gallons of water through it. I cleaned both water inlet screens. I cleaned the air filter screen. I checked incoming gas pressure and that was according to manufacturer specifications. Lastly I ran the unit and everything was running great. The whole house humidifier hasn't been maintenance before. It should be done every year. I will send over an estimate for the maintenance. The first floor bathroom toilet is clogged. I tried unclogging it with a plunger and that didn't work so we will have to come back and snake it.
Completed the plumbing inspection today. I checked all the fixtures and drains and everything looked great. I labeled a few emergency shut offs. I completed the rinnai water heater maintenance today as well. I started off with running cleaner through it for about 40 minutes. After I flushed 10 gallons of water out. I cleaned the water inlet screen. I cleaned the air filter screen as well. I checked incoming gas pressure and that was according to manufacturer specifications. I cleaned the electrode and flame sensors. Lastly I ran the hot water and it was working great.
Always amazing service, every team member at GSMS has always been great and performed exceptionally great service.
Excellent Service
Very nice and personable person. Explained everything to me in a way I could understand
I never thought I’d meet anyone as cool nice and kind as Mark but Jack was amazing. He took on the dirty job.. No problem He was super communicative and explained everything. I’m really grateful to have Granite State Mechanical on speed dial.
Jack was once again on time, diagnosed the problem quickly and fixed it. All GSMS staff are courteous and extremely professional. I wouldn’t go with anyone else.
Excellent work
Great service!
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.
No heat emergency situation handled immediately on a Sunday evening. Great service!
Excellent service
Love dealing with this company. Their techs are always prompt, efficient and courteous. We've been happy to be their customer since 2010.
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
Qwentin was on time, very friendly and professional. He was able to identify the issue, communicate it effectively, and then fix it. Highly recommend.
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
Great water heater service. On time and professional l He gave me some helpful tips on other water related issues. Highly recommend GSMS.
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
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
top notch service, always professional. would recommend to anyone needing HVAC service, repair or install.
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!
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
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!
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.
We thank you for sharing your positive experience. It made our day.
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