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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 117 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
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
Mark D.
Mark D. Checked in
Found both body sprays plugged.Bob is going to buy body sprays,hand held shower and. New shower head.
Sandown, NH 03873
Bow, NH - Pm on rinnai
Mark D.
Mark D. Checked in
Pm on rinnai
Bow, NH 03304
Mark D.
Mark D. Checked in
We are going to install the InSinkErator Evolution 1 HP (Advanced Series). While it matches the 1-horsepower strength of your previous unit, the technology inside is completely different. Your old disposal used a single grinding ring, but this new Evolution model uses 4-Stage MultiGrind™ technology. What that means for you: It Liquefies Everything: It has special 'shear rings' and 'undercutters' that slice food into near-liquid form. It can handle things your old unit couldn't, like celery and potato peels, without jamming. It's Silent: It features the highest level of 'SoundSeal' insulation, making it the quietest disposal on the market—you will barely hear it running compared to your old one.
Bedford, NH 03110
Mark D.
Mark D. Checked in
Replaced basement toilet supply line
Manchester, NH 03104
Mark D.
Mark D. Checked in
From your Home Club visit, Qwentin identified the 1-1/2" sump pump waste line has a failed joint as the coupling. We will cut out the failed fitting and install a new small section of pipe and fitting.
Hopkinton, NH 03229
Mark D.
Mark D. Checked in
Found front outside faucet on,hose broke and water was running outside.Installed shut off by well tank for outside faucet.cleaned aerator on faucets and shower heads also adjusted 2 toilets.
Londonderry, NH 03053
Replaced flapper in seco d floor toilet
Replaced flapper in seco d floor toilet
Mark D.
Mark D. Checked in
Replaced flapper in seco d floor toilet
Manchester, NH 03104
Deerfield, NH - We will replace the one-piece fiberglass shower unit in the basement bathroom due to mold growth. We will demo and remove the existing tub unit and cap off the water and waste lines.

A new Sterling Accord 48" shower unit will replace the one-piece unit. This unit will be installed with new connections and drain and a new Moen polished chrome shower valve with a standard shower head.

The client will be responsible for the carpentry work. This work will be done, understanding that mold remediation will be completed between the project.Install customers toilet.lav faucet and install clean out in kitchen drain line.
Mark D.
Mark D. Checked in
We will replace the one-piece fiberglass shower unit in the basement bathroom due to mold growth. We will demo and remove the existing tub unit and cap off the water and waste lines. A new Sterling Accord 48" shower unit will replace the one-piece unit. This unit will be installed with new connections and drain and a new Moen polished chrome shower valve with a standard shower head. The client will be responsible for the carpentry work. This work will be done, understanding that mold remediation will be completed between the project.Install customers toilet.lav faucet and install clean out in kitchen drain line.
Deerfield, NH 03037
Completed the gas furnace maintenance today. I started off with checking all the electrical connections and everything looked good. I pulled the flame sensor and I cleaned it. The filter looks brand new. I checked incoming and outgoing gas pressures and those were according to manufacturer specifications. Lastly I ran the unit and performed a combustion analyzer test that checks the units CO, CO2 and oxygen levels and it was running great. The condensate pump has failed at some point so it is leaking water on the floor. There is no drain line either so we would have to figure out where to put that. The heat and the AC both produce water. Let us know if you would like that done and we would be happy to help. If you plan on using the AC in the summertime I would highly recommend doing a AC maintenance, we would come back out in the spring/summer time.
Completed the gas furnace maintenance today. I started off with checking all the electrical connections and everything looked good. I pulled the flame sensor and I cleaned it. The filter looks brand new. I checked incoming and outgoing gas pressures and those were according to manufacturer specifications. Lastly I ran the unit and performed a combustion analyzer test that checks the units CO, CO2 and oxygen levels and it was running great. The condensate pump has failed at some point so it is leaking water on the floor. There is no drain line either so we would have to figure out where to put that. The heat and the AC both produce water. Let us know if you would like that done and we would be happy to help. If you plan on using the AC in the summertime I would highly recommend doing a AC maintenance, we would come back out in the spring/summer time.
Mark D.
Mark D. Checked in
Completed the gas furnace maintenance today. I started off with checking all the electrical connections and everything looked good. I pulled the flame sensor and I cleaned it. The filter looks brand new. I checked incoming and outgoing gas pressures and those were according to manufacturer specifications. Lastly I ran the unit and performed a combustion analyzer test that checks the units CO, CO2 and oxygen levels and it was running great. The condensate pump has failed at some point so it is leaking water on the floor. There is no drain line either so we would have to figure out where to put that. The heat and the AC both produce water. Let us know if you would like that done and we would be happy to help. If you plan on using the AC in the summertime I would highly recommend doing a AC maintenance, we would come back out in the spring/summer time.
Pelham, NH 03076
Replace valve and supply and install toilet
Replace valve and supply and install toilet
Mark D.
Mark D. Checked in
Replace valve and supply and install toilet
Pelham, NH 03076
Mark D.
Mark D. Checked in
Replace filters on reverse O system
Hooksett, NH 03106
Epsom, NH - Replace failed combustion chamber with new.
Mark D.
Mark D. Checked in
Replace failed combustion chamber with new.
Epsom, NH 03234
Mark D.
Mark D. Checked in
Cut ceiling to locate drain for tub.
Bedford, NH 03110
Epsom, NH - Combustion camber fell on oil burner causing it to soot up .Cleaned boiler check adjustments.Will send estimate to replace combustion chamber.
Mark D.
Mark D. Checked in
Combustion camber fell on oil burner causing it to soot up .Cleaned boiler check adjustments.Will send estimate to replace combustion chamber.
Epsom, NH 03234
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
Review
Excellent Service
Sharon - Merrimack, NH 03054
Trusted Quality & Service