Where do we find the water system check valve (if any) and why are check valves used on pump and well systems?
Well pump & water tank diagnosis & repair procedures
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This article explains water supply piping check valves used on both municipal water supply piping (usually near the water meter) and on private pump and well water supply systems (usually near the well pump).
Readers of this document whose building is served by a well, pump, and water tank system should also see WELL PIPING FOOT VALVES.
On a well and pump water supply system a check valve may be installed between the incoming water line from the well and the water pump and pressure tank, such
as shown in this photograph of a one line jet pump with a check valve right at the water pump inlet.
You can see the check valve as a bronze assembly at the face of the pump, connected to well piping in this photo.
(A similar check valve is visible closer to the foundation wall in a different water pump installation shown in the page top photo.)
You'll notice that this is a one-line jet pump system with the
inlet or suction line from the well running horizontally from the face of the pump, and the outlet water line rising vertically off of the
pump assembly. The pump's electric motor is at the rear of the assembly. (You can see corrosion and leaks on the
water line rising from the pump assembly.)
The water pump check valve helps avoid loss of prime (it keeps water from flowing backwards out of the pump and water tank
and back into the well when the pump motor has stopped).
Our photos above show a tpyical brass well piping check valve. A spring-loaded internal valve permits water to flow through the valve only in one direction. The check valve helps assure that the jet pump can suck water out of a shallow well - most water pumps
cannot move water if the inside of the pump assembly itself is air bound. Atop some pump assemblies you'll see a removable pipe plug which permits
water to be poured into the pump to prime it. (DO NOT pour water into or onto the electric motor itself.)
In summary, a well piping check valve prevents water from
siphoning back out of the water tank and water pump and down into the (presumably lower) water well when the pump stops running.
A check valve at this location is a great idea and reduces the risk that a failure
of the foot valve down in the well leads to inability of the pump to draw water. The foot valve s located at the bottom of the well piping and intended to accomplish the same thing. This
is "cheap insurance" or perhaps the foot valve has already failed (or was omitted) at this installation.
Check Valves on Municipal Water Supply Piping
You may see check valves installed on municipal water supply piping too, to prevent possibly unsanitary water from inside a building's piping from back-flowing into and contaminating the municipal water supply
system piping during a time of loss of municipal water pressure.
Check valves installed at the right location on water system piping are a good idea and are required by national and local plumbing codes in many jurisdictions.
Check valves are also installed on drain piping such as on some sewer lines (where sewer backups are likely) and on sump pumps (discussed below).
Other Applications of Check Valves on Building Plumbing & Piping
Check valves on sump pumps: Check valves are used in other plumbing applications as well, such as on sump pump drain lines to prevent back-flow of water from the sump pump exit piping into the sump pit when the sump pump turns off.
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General water testing and corrective measure advice: contact your local health department.
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