Rating
Reviews
LICENSES: MASTER PLUMBER, GAS SERVICE
Mark started GSMS in 1987 with a single van and a commitment to doing things the right way. While he has transitioned the company to the second generation, Mark’s passion for the trade keeps him in the field every day. You’ll still find him visiting clients, sharing his 40 years of expertise, and ensuring the Downing standard is met on every call.
Name: Mark Downing
GSMS Air•Heating•Plumbing has completed 25 jobs between September 2026 and November 2026.
The 15 customer reviews shown here average 4.8 out of 5.
The most recent job was on November 5, 2026.
Recent work covers Manchester, NH, Bedford, NH, Nashua, NH, Amherst, NH and Merrimack, NH.
Replaced shower cartridge
Replaced basket strainer and order brass basket strainer
Checked plumbing pressure is 60 psi,plumbing looked good outside faucet by garage is bad
Pm on oil furnace
Pm on furnaces check gas pressures,cleaned flame sensor,replaced cut to fit filter on first floor unit and replaced basement air bear 20x25x5
Removed toilet and snake main line.Blocked with solids.
As always very easy to work with GSMS, professional and timely with no unexpected issues or problems.
Install toilet
.replace blower motor and flame sensor
Tune up boiler
Install new 3/4" check valve and two 3/4" ball valves on water meter
Oil furnace pm and replace first floor thermostat
.installed water filter and replaced shower cartilage
Replaced thermocouple and low water cut off
Replace draft inducer motor
Check furnace for winter,check all controls,gas pressure and cleaned flame sensor everything this fine
Finished plumbing work
Check expansion tank and cleaned screen on pressure reducing valve
Water test
While your furnace is currently operational, it was installed with the home in 2016, putting it at the 10-year mark (furnaces typically last 15-20 years, while ACs last 10-15). Why consider replacing the whole system now? Replacing the furnace and AC together saves a massive amount of duplicate labor costs compared to replacing the AC now and the furnace a few years later. Furthermore, installing a complete, brand-new Lennox system guarantees an "AHRI Matched" system—meaning the furnace and AC were engineered specifically to work together for maximum efficiency. This option provides a direct, high-quality replacement for your entire current setup. Scope of Work 1. Demolition We will safely recover the old refrigerant and completely remove the existing AC, indoor coil, and aging 2016 furnace. 2. Full System Equipment (Lennox Merit) The Furnace: We will install a reliable, new Lennox Merit single-stage gas furnace. Air Conditioner: We will install a new Lennox Merit single-stage
Repaired cold waterline on hot water heater
Replaced gas valve
Scope of Work: Upgrade to a High-Efficiency US Boiler Alta Series system, offering superior energy savings, quiet operation, and modern sealed-combustion technology. Heating & Hot Water: Boiler Installation: The new high-efficiency wall-hung unit will be installed in the basement, on the wall in the vacinity of the old boiler. Domestic Hot Water: This boiler is a combi model so it will act as a tankless water heater, providing domestic hot water for the home. Expect an additional 30-second delay in heating. Condensate Management: As a high-efficiency unit, this system produces condensate (water). We will install a condensate pump to route this moisture automatically to the available basement drain. Venting (Sidewall): Chimney Retirement: The existing chimney will be capped off and no longer used. New Intake/Exhaust: We will install new PVC fresh air intake and Centrotherm exhaust piping. These lines will route through the unfinished basement ceiling and penetrate the exterior wa
Remove toilet and reset
Mark is careful, thorough, and has very helpful suggestions.
This proposal covers the complete removal of your existing standard bathtub and the professional installation of a premium Walk-In Therapy Tub. To ensure this new therapeutic tub fills quickly and operates flawlessly, we will be heavily upgrading the underlying plumbing to 3/4" lines and running new dedicated electrical circuits to power the jets and inline heater. We will also be coordinating with our trusted partner, Scott, to handle the final tile, drywall, and paint restoration once the plumbing installation is complete. Scope of Work 1. Demolition & Area Preparation Tear-Out: We will carefully disconnect and remove the existing bathtub and immediate wall surrounds. Debris Removal: All old tub materials and job site demolition debris will be hauled away and properly disposed of. Area Prep: We will prep the exposed floor and framing to securely accept the new, heavier walk-in tub unit. 2. Plumbing Rough-In & Upgrades Water Line Upsizing: Walk-in tubs require high water volume
Great service as always. Thank you so very much for squeezing us in! We are very grateful.
Set toilet
CALL BACK IS IN THE WORKS- THERMOSTAT IS BLACK - NO REPSOPONSE.
Extremely professional and on time, great work! Highly recommend their services.
As always very professional
Mark and his team came in install my new kitchen appliances. I switched from gas to induction for my stove, replaced my over the oven microwave and replaced my refrigerator so they installed my water line so now I have an ice maker!
Totally fixed my problem in short time. Always do neat as well
Mark was very professional, found an issue with the system, fixed it.
Exceptional service
I had a need to replace the shutoff valve from the main water supply to the building per the water utilities company. Mark worked with the water utilities company to coordinate the work that needed to be done and installed a new shutoff valve.
Issues resolved quickly and efficiently
Great work and kept me informed the entire time. Did a great job, fast, clean, and customer-focused. Highly recommend.
Mark was on time (on the early side of the timeframe) and throughly checked out the ac and plumbing. Pleasant demeanor and went over everything he did and gave the systems a good bill of health.
Excellent service!
