🏆 We Won the 2026 BBB Torch Award!
Request Service Call Now Contact Us Coupons

Mark Downing

Mark Downing

Founder / Service Specialist

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 39 years of expertise, and ensuring the Downing standard is met on every call.

Name: Mark Downing

Recent Jobs and Reviews

Rated 5.0 out of 5 stars based on 130 customer reviews

Customers say: The overall sentiment across these reviews is overwhelmingly positive, reflecting high levels of customer satisfaction and appreciation. Customers consistently express enthusiasm about the quality of service they received, with recurring praise for professionalism, expertise, and efficiency. A dominant theme throughout is the technical skill and knowledge demonstrated by the service team, with many reviewers highlighting how thoroughly problems were diagnosed and resolved. The interpersonal qualities of the technicians emerge as another strong positive trend, with customers frequently describing them as friendly, personable, pleasant, and respectful. Communication stands out as a particularly valued aspect, with reviewers appreciating clear explanations, patience in answering questions, and being kept informed throughout the service process. Timeliness and punctuality are consistently mentioned as strengths, alongside respect for customers' property and maintaining clean, orderly work practices. Many customers express strong loyalty and trust in the company, with several indicating they are repeat customers or plan to continue using the service. The tone is enthusiastic and grateful, with multiple reviewers offering strong recommendations and expressing genuine happiness with the results. Overall, these reviews paint a picture of a service provider that excels in both technical competence and customer care, creating consistently positive experiences that foster long-term customer relationships.

Job Locations and Reviews

Mark D.
Mark D. Checked in
Removed baseboard in tv rm and repaired leak
Wilton, NH 03086
Changed water filter.flushed water and replaced anode rod
Changed water filter.flushed water and replaced anode rod
Mark D.
Mark D. Checked in
Changed water filter.flushed water and replaced anode rod
Wilton, NH 03086
Did water test and checked plumbing system
Did water test and checked plumbing system
Mark D.
Mark D. Checked in
Did water test and checked plumbing system
Auburn, NH 03032
Mark D.
Mark D. Checked in
Repaired leak in garage,installed outside faucet,replaced water filter,removed rain head from second floor bath rm and installed temperaily shower head
Londonderry, NH 03053
Install check valves on hot and cold outside faucet
Install check valves on hot and cold outside faucet
Mark D.
Mark D. Checked in
Install check valves on hot and cold outside faucet
Amherst, NH 03031
Review
Extremely professional and on time, great work! Highly recommend their services.
Georgine - Bedford, NH 03110
Manchester, NH - Changed uv bulb checked air filter and condensate drain,wash outside coil checked charge and controls
Mark D.
Mark D. Checked in
Changed uv bulb checked air filter and condensate drain,wash outside coil checked charge and controls
Manchester, NH 03103
Mark D.
Mark D. Checked in
Replaced garbage disposal,Lite pilot on fireplace burners would not come on,looks like bad thermopile had customer call all basic for repair.Pm on furnace cleaned air filter and flame sensor Check gas pressure in coming was 5.87 wc manifold was 4.8 adjusted to name plate which is 3.5 wc
Bedford, NH 03110
Mark D.
Mark D. Checked in
Pm on a/c washed outdoor coil,checked capacitor on outdoor unit,Indoor unit checked condensate drain and filter
Nashua, NH 03064
Mark D.
Mark D. Checked in
Checked air filter, condensate trap both ok.Filter is schedule 10/20/26 to be changed.cleaned air exchanger filters.Wash outdoor coil everything checked out fine
Henniker, NH 03242
Replaced cartridge
Replaced cartridge
Mark D.
Mark D. Checked in
Replaced cartridge
Barrington, NH 03825
Installed hanger on dishwasher line
Installed hanger on dishwasher line
Mark D.
Mark D. Checked in
Installed hanger on dishwasher line
Northwood, NH 03261
Mark D.
Mark D. Checked in
Pm on first floor unit,replaced filter and washed outside unit Pm on mimi spilt in apartment by tv,cleaned indoor and outdoor coil also washed filters. Pm on mini spilt in loft area of apartment,cleaned indoor and outdoor coil washed air filters. Pm on mini spilt in main house on second floor bed rm cleaned indoor and outdoor coil washed filters
Hollis, NH 03049
Review
As always very professional
Steve - Nashua, NH 03064
Mark D.
Mark D. Checked in
Serviced 2 a/c units,put dye and sealant in second floor unit has a leak
Merrimack, NH 03054
Mark D.
Mark D. Checked in
Replaced bad blower motor and capacitor,sprayed indoor coil with coil cleaner and disinfectant,washed condenser coil and replaced air filter.
Manchester, NH 03109
Mark D.
Mark D. Checked in
Replaced cap
Manchester, NH 03104
Review
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!
Terry - Manchester, NH 03109
Mark D.
Mark D. Checked in
To ensure a seamless transition from your old appliances to your new ones, this project will be completed in two separate phases. You will coordinate your delivery day directly with Barons, and GSMS will schedule our visits around that date to allow for the safe removal of the old units and the proper mechanical installation of the new units. Phase 1: Pre-Delivery Disconnect (The Day Before Delivery) Gas Line Safe-Off: Prior to the delivery of your new appliances, a GSMS Service Specialist will disconnect your existing gas stove. We will trace the gas line to the basement and safely cap it off at the source. The physical piping will be left in place to allow for an easy conversion back to gas in the future, should you or a future owner desire it. Phase 2: Appliance Connection & Installation (The Day After Delivery) Once Barons has removed the old units and placed the new units in the kitchen, GSMS will return to complete the final connections: Induction Range Electrical: We will sw
Manchester, NH 03109
Review
Totally fixed my problem in short time. Always do neat as well
Sandra - Bedford, NH 03110
Mark D.
Mark D. Checked in
Clean sink drain and removed instant hot
Bedford, NH 03110
Mark D.
Mark D. Checked in
Pm on a/c system checked indoor blower and condensate pump.Outdoor unit washed coil,checked capacitor and refrigerant charge.Everything checked out good.
Bedford, NH 03110
Completed PM on all rooftop units, including changing filters, washing outside coils, and changed belts on exhaust fans.

The rear boarding room unit we had to replace the contactor.

The Rheem rooftop unit we had to replace the control board due to a short in one of the wires.

The breakroom unit that was leaking water, we found due to plugged filters and dirty evaporative coil.

We highly encourage an ongoing Service Agreement to keept his equipment lasting as long as possible.
Completed PM on all rooftop units, including changing filters, washing outside coils, and changed belts on exhaust fans.

The rear boarding room unit we had to replace the contactor.

The Rheem rooftop unit we had to replace the control board due to a short in one of the wires.

The breakroom unit that was leaking water, we found due to plugged filters and dirty evaporative coil.

We highly encourage an ongoing Service Agreement to keept his equipment lasting as long as possible.
Mark D.
Mark D. Checked in
Completed PM on all rooftop units, including changing filters, washing outside coils, and changed belts on exhaust fans. The rear boarding room unit we had to replace the contactor. The Rheem rooftop unit we had to replace the control board due to a short in one of the wires. The breakroom unit that was leaking water, we found due to plugged filters and dirty evaporative coil. We highly encourage an ongoing Service Agreement to keept his equipment lasting as long as possible.
Manchester, NH 03103
Mark D.
Mark D. Checked in
Cap stove gas line
Nashua, NH 03063
Mark D.
Mark D. Checked in
Estimate on toilet and fiberglass wash sink also gasoline for log set
Nashua, NH 03064
Mark D.
Mark D. Checked in
Replaced outside faucet,Did est for toilet replacement
Amherst, NH 03031
Mark D.
Mark D. Checked in
remove pressure switch sensor from combustion blower clear blockage applied RTV and reinstalled. System running fine.
Amherst, NH 03031
Review
Mark was very professional, found an issue with the system, fixed it.
Craig - Madbury, NH 03823
Mark D.
Mark D. Checked in
Adjusted gas pressure
Madbury, NH 03823
Mark D.
Mark D. Checked in
Flushed antifreeze from shower,mounted outdoor faucet,removed broken intake screen from hot water heater fresh air pipe and installed new one
Seabrook, NH 03874
Review
Exceptional service
Paul - Nashua, NH 03062
Review
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.
LoriB - Milford, NH 03055
Review
Issues resolved quickly and efficiently
Mark - York, ME 03909
Review
Great work and kept me informed the entire time. Did a great job, fast, clean, and customer-focused. Highly recommend.
Gregory - Auburn, NH 03032
Review
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.
Nelson - Merrimack, NH 03054
Review
Excellent service!
Sharon - Merrimack, NH 03054
Review
Friendly, thorough and efficient!
Bob - Sandown, NH 03873
Review
Glad to see the ole man still working!! LOL
Phil - Windham, NH 03087
Review
Excellent service and communication. A great family business.
Paul - Nashua, NH 03062
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
Trusted Quality & Service