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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 118 customer 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

Mark D.
Mark D. Checked in
Made list for bypass need to connect control for air to air
Manchester, NH 03102
Installed 2 silcocks and one hot&cold silcock
Installed 2 silcocks and one hot&cold silcock
Mark D.
Mark D. Checked in
Installed 2 silcocks and one hot&cold silcock
Manchester, NH 03103
Mark D.
Mark D. Checked in
Check main drain found it block a d rusting on top of pipe.Recomend replaces pipe
Nashua, NH 03064
Mark D.
Mark D. Checked in
Installed shower head
Exeter, NH 03833
Review
Glad to see the ole man still working!! LOL
Phil - Windham, NH 03087
Mark D.
Mark D. Checked in
Done not starting do to bad float switch.Replaced switch and cleaned pump housing
Windham, NH 03087
Mark D.
Mark D. Checked in
Remove second d floor toilet and replace was gasket and closet bolts.Replace 22' of 1/2" l copper pipe and installed new valve.
Manchester, NH 03104
Mark D.
Mark D. Checked in
found air trapped in second floor coil purged air from system everything's running fine
Hollis, NH 03049
Mark D.
Mark D. Checked in
install customer sink and toilet
Hooksett, NH 03106
Mark D.
Mark D. Checked in
Sewer main clogged. Stuck open flapper on second floor caused water to come out of toilet near kitchen. Need snake and camera inspection. Thank you!
Amherst, NH 03031
Nashua, NH - Proposal to replace the three existing A/C systems at Montcalm Properties: 
System A (serving the second floor of Corriveau Insurance Agency)
System B (serving the third floor area for the church / conference room)
System C (serving the front offices of the third floor).

System A (Corriveau Insurance Agency - Second Floor): This will be a direct replacement. The existing wall return grille in the hallway space will be upsized to a larger size to provide proper airflow for the new system. Due to installation limitations, the existing lineset for System A will remain in place and be thoroughly flushed and cleaned out for the new unit.

System B (Church / Conference Room - Third Floor): This will be a direct replacement. This system is sized to handle capacity for either the conference room or church space. System B will receive a new lineset.

System C (Front Offices - Third Floor): This system will be upsized to a 5-ton capacity. Two return grilles in the hallway will be replaced and i
Mark D.
Mark D. Checked in
Proposal to replace the three existing A/C systems at Montcalm Properties: System A (serving the second floor of Corriveau Insurance Agency) System B (serving the third floor area for the church / conference room) System C (serving the front offices of the third floor). System A (Corriveau Insurance Agency - Second Floor): This will be a direct replacement. The existing wall return grille in the hallway space will be upsized to a larger size to provide proper airflow for the new system. Due to installation limitations, the existing lineset for System A will remain in place and be thoroughly flushed and cleaned out for the new unit. System B (Church / Conference Room - Third Floor): This will be a direct replacement. This system is sized to handle capacity for either the conference room or church space. System B will receive a new lineset. System C (Front Offices - Third Floor): This system will be upsized to a 5-ton capacity. Two return grilles in the hallway will be replaced and i
Nashua, NH 03060
Mark D.
Mark D. Checked in
We will safely remove your existing, cracked double-basin wash sink and upgrade your basement laundry area with a new, durable Mustee utility tub. During this installation, our team will also upgrade the surrounding water lines and reconfigure the drainage to a highly reliable, gravity-fed system. Scope of Work: Demolition & Removal: Disconnect and carefully remove the existing leaking double-basin sink. (The existing back wall will remain in place and untouched). New Sink Installation: Provide and install a new Mustee 40-inch floor-mount utility wash tub. Faucet & Water Lines: Provide and install a standard center-set, polished chrome utility faucet. We will modify the existing copper water piping and install brand-new, reliable shutoff valves for the new sink. Drainage Reconfiguration (Pump Elimination): Originally, we discussed installing a mechanical drain pump to handle the wastewater. However, after our Master Plumber reviewed your specific plumbing stack, we engineered a be
Manchester, NH 03102
Replaced grill on top of a/c unit,cleaned a/c outdoor coil.Outdoor unit coil will need to be replaced.Salt is eating away the coil.Based on age of unit you should replace entire unit.Turned all water on and flushed system.Cleaned indoor filter and outdoor coil on third floor unit.Fireplace pilot valve needs to be turn to 6 o'clock piston were it says on.Checked fire pit.
Replaced grill on top of a/c unit,cleaned a/c outdoor coil.Outdoor unit coil will need to be replaced.Salt is eating away the coil.Based on age of unit you should replace entire unit.Turned all water on and flushed system.Cleaned indoor filter and outdoor coil on third floor unit.Fireplace pilot valve needs to be turn to 6 o'clock piston were it says on.Checked fire pit.
Mark D.
Mark D. Checked in
Replaced grill on top of a/c unit,cleaned a/c outdoor coil.Outdoor unit coil will need to be replaced.Salt is eating away the coil.Based on age of unit you should replace entire unit.Turned all water on and flushed system.Cleaned indoor filter and outdoor coil on third floor unit.Fireplace pilot valve needs to be turn to 6 o'clock piston were it says on.Checked fire pit.
Wells, ME 04090
Mark D.
Mark D. Checked in
I found the release valve dripping caused by a bad expansion tank. I replace the expansion tank and Purge the system
Hollis, NH 03049
Mark D.
Mark D. Checked in
Replacement of existing corner shower, 34" x 34". We will remove existing shower unit, glass enclosure, and old plumbing as needed. For the tile floor, the goal is to chip away the mortar edge between the tile and the existing shower base. If this is achieved, there will be minimal finish work required afterward. In the worst-case scenario, the first row of tiling closest to the existing shower base will need to be removed. A new MAAX rounded corner 32" shower will be installed in place. A matching MAAX glass sliding door enclosure will also be installed for the unit. The glass enclosure has a polished chrome finish with clear, smooth glass. A standard Moen Chateau shower valve with a shower arm will be installed in polished chrome. The client will source and provide a showerhead to be installed. The client is responsible for finish work - including drywall edging around shower walls (where drywall abuts shower walls) and tile flooring. GSMS will dispose of trash/debris.customer wi
Exeter, NH 03833
Mark D.
Mark D. Checked in
A faulty fill valve was identified so we replaced with a new one.
Hampton, NH 03842
Mark D.
Mark D. Checked in
Filled heating system and purged zones.Filled water system had to replace well tank gauge.Gauge was broken showing 100psi.Replace toilet handle and flapper on first floor toilet.Second floor toilet needs fill valve left it off.No shower head on second floor shower.Basement toilet pump doesn't shut off left it unplugged.
Barrington, NH 03825
Mark D.
Mark D. Checked in
Installed. New water lines&jack installed new heater.Jack will finish heater tomorrow and install toilet.I need to go back to install plumbing and pump to new sink.Also Eric wants hot and cold outside faucet
Exeter, NH 03833
Mark D.
Mark D. Checked in
Install valves for kitchen sink and replace sprayer
Newmarket, NH 03857
Mark D.
Mark D. Checked in
Replaced fill valve on toilet
Newmarket, NH 03857
Install bath rm fan
Install bath rm fan
Mark D.
Mark D. Checked in
Install bath rm fan
Nashua, NH 03064
Mark D.
Mark D. Checked in
Cut open wall to repair drain.Have to come back water treatment equipment was draining into line.
Pelham, NH 03076
Mark D.
Mark D. Checked in
Replaced gas valve under warranty
Barrington, NH 03825
Review
Excellent service and communication. A great family business.
Paul - Nashua, NH 03062
Mark D.
Mark D. Checked in
Checked system everything looked fine added a couple of han gers.She doesn't like the thermostat we put in going to look for simple with better df.
Merrimack, NH 03054
Nashua, NH - This is the ultimate purity option, using advanced "smart" technology and a space-saving design.

Scope of Work: Install a DROP Smart RO unit horizontally in the cabinet beneath the kitchen sink.

Space-Saving Design: Because this unit is an all-in-one system, it does not require a separate large holding tank. We will install it horizontally in front of the garbage disposal to maximize your remaining cabinet space.

Primary Benefit: Removes up to 99% of contaminants (lead, fluoride, arsenic, and PFAS) while delivering the highest quality drinking water available.

Smart Features: * Built-in Leak Protection: Automatically shuts off the water if it detects a leak under the sink.

Real-Time Monitoring: Sends alerts to your phone via the DROP App when it's time to change filters.

UV Disinfection: Includes a built-in UV stage to ensure the water is bacteriologically safe.

Utility Requirements: This unit requires a 110V electrical outlet to power the internal pumps and smart features.

Gra
Mark D.
Mark D. Checked in
This is the ultimate purity option, using advanced "smart" technology and a space-saving design. Scope of Work: Install a DROP Smart RO unit horizontally in the cabinet beneath the kitchen sink. Space-Saving Design: Because this unit is an all-in-one system, it does not require a separate large holding tank. We will install it horizontally in front of the garbage disposal to maximize your remaining cabinet space. Primary Benefit: Removes up to 99% of contaminants (lead, fluoride, arsenic, and PFAS) while delivering the highest quality drinking water available. Smart Features: * Built-in Leak Protection: Automatically shuts off the water if it detects a leak under the sink. Real-Time Monitoring: Sends alerts to your phone via the DROP App when it's time to change filters. UV Disinfection: Includes a built-in UV stage to ensure the water is bacteriologically safe. Utility Requirements: This unit requires a 110V electrical outlet to power the internal pumps and smart features. Gra
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
Scope of Work

1. Laundry Relocation
Water & Waste: Relocate hot and cold water lines, washing machine drain, and vent piping into the newly built closet area.
Framing Coordination: Adjust framing as discussed (specifically the double stud) to accommodate the new plumbing layout.
Exclusions: This quote does not include the installation of dryer venting or gas piping for the dryer.

2. Shower Installation
Drainage: Install a new 2" shower drain, pulling the location back to the center of the new shower floor layout. Connect to the existing vent system.
Water Supply: Route new hot and cold water lines.
Valve: Install a standard pressure-balancing shower valve and a drop ear elbow for a single shower head outlet.

3. Toilet (Same Location)
Drainage: Install a new 3" toilet flange to ensure a proper seal.
Water Supply: Install a new cold water supply line and shut-off valve.

4. Vanity (Same Location)
Rough-in: Install two (2) new water supply valves and adjust the drain trap.
Trim: Connec
Scope of Work

1. Laundry Relocation
Water & Waste: Relocate hot and cold water lines, washing machine drain, and vent piping into the newly built closet area.
Framing Coordination: Adjust framing as discussed (specifically the double stud) to accommodate the new plumbing layout.
Exclusions: This quote does not include the installation of dryer venting or gas piping for the dryer.

2. Shower Installation
Drainage: Install a new 2" shower drain, pulling the location back to the center of the new shower floor layout. Connect to the existing vent system.
Water Supply: Route new hot and cold water lines.
Valve: Install a standard pressure-balancing shower valve and a drop ear elbow for a single shower head outlet.

3. Toilet (Same Location)
Drainage: Install a new 3" toilet flange to ensure a proper seal.
Water Supply: Install a new cold water supply line and shut-off valve.

4. Vanity (Same Location)
Rough-in: Install two (2) new water supply valves and adjust the drain trap.
Trim: Connec
Mark D.
Mark D. Checked in
Scope of Work 1. Laundry Relocation Water & Waste: Relocate hot and cold water lines, washing machine drain, and vent piping into the newly built closet area. Framing Coordination: Adjust framing as discussed (specifically the double stud) to accommodate the new plumbing layout. Exclusions: This quote does not include the installation of dryer venting or gas piping for the dryer. 2. Shower Installation Drainage: Install a new 2" shower drain, pulling the location back to the center of the new shower floor layout. Connect to the existing vent system. Water Supply: Route new hot and cold water lines. Valve: Install a standard pressure-balancing shower valve and a drop ear elbow for a single shower head outlet. 3. Toilet (Same Location) Drainage: Install a new 3" toilet flange to ensure a proper seal. Water Supply: Install a new cold water supply line and shut-off valve. 4. Vanity (Same Location) Rough-in: Install two (2) new water supply valves and adjust the drain trap. Trim: Connec
Strafford, NH 03884
Review
Friendly and transparent. Explained all aspects of the service.
Jeffrey - Nashua, NH 03064
Review
A+
Scott - Nashua, NH 03064
Review
The experience started with Gina in the office who was very responsive and accommodating and made the scheduling process super efficient and friendly. Then Mark came and brought his expertise to my home and systems to point areas of installation failures by the company that installed my system. Just using the basic manual to point out how they cut corners. Mark spent the time to correct the exhaust piping to fix leaks and improve air flow. He was friendly and accommodating.
Nelson - Merrimack, NH 03054
Review
Whenever Mark is on the way, you know it’s gonna be fixed correctly. He is awesome!
Kathleen - Nashua, NH 03064
Review
Mark is always very professional and clearly communicates all options. He and his team are able to accommodate us and get the job done in a timely manner. THANK YOU!
Joyce - Hudson, NH 03051
Review
Arrived on time. Work was completed timely. Cleaned up afterwards. Very pleased with the service.
Charlie - New Boston, NH 03070
Review
GSMS is a great Family owned Company to work with. I am very happy with my new Boiler heating system. Zak explained all my options and was prompt to call back with any questions I had. Adam, the lead Technician was outstanding with the installation. Gina was great coordinating the scheduling. Mark also came out for a final inspection. You can tell they take pride in their work! I would definitely recommend them.
Sandy - Nashua, NH 03060
Review
Great seeing Mark again.
Bob - Nashua, NH 03062
Review
Completed job in a timely fashion attention to detail would hire again
Edward - Goffstown, NH 03045
Review
Service
Guimont - Manchester, NH 03103
Review
Our furnace kept shutting off. Mark identified the issue and resolved the problem. Very much appreciate the service!
Oakwood Prop - Milford, NH 03055
Review
Excellent service
Kathleen - Merrimack, NH 03054
Trusted Quality & Service