gate valve question

[moorem]

Hi. I installed a new Pressure reducing valve just above my main water valve in the basement. Theres a pinhole leak on one of the solder joints, so I need to drain the system and re solder it. The gate valve just below the PRV has a small screw cap on the side of it. Can I unscrew this to drain the line? I'm not sure if a spring or anything will pop out and I dont want to resolder the whole thing unless I absolutely have to. I hope this makes sense. Thanks as always!

[LazyPup]

Whenever a line stop valve has the little drain port on the side such as you describe it is technically called a "Stop & Waste" valve.

Once the stop valve is closed you can remove the little waste cap to drain the water out of the line on the downstream side of the valve only. The waste port is simply an open port into the valve with a threaded cap so there is no worry about springs or other components coming out when you remove the cap.

Stop and waste valves are commonly used in areas that are subject to freezing to protect outside hose bibbs in winter. The stop & Waste should be installed at least 3' inside the structure. In winter the stop & waste valve is turned off. You then open the waste port to vent air into the line to insure the residual water in the line will drain out through the hose bibb. Once it is drained replace the waste cap but leave the hose bibb open all winter. By leaving the hose bibb open and water that may leak past the stop valve will drain out, therefore there is no water in the line that may freeze and damage the valve or line. Stop and waste valves are also commonly used as zone valves so you may shut a zone off and drain that portion of the system for maintenance without turning the main water supply off.

If I am understanding your description correctly, your main water line is coming in below this valve and the line then turns vertical to this valve. The PRV and the joint that you need to resolder are then at some point above the Stop & Waste valve.

You must keep in mind that there is a substantial quantity of residual water in the distribution piping above this valve.

The first step is to drain as much of the standing water out of the system as possible. If we were to try draining it from the waste port it would take a couple hours.

Begin by turning the "Main Water Shutoff" valve off, then open a faucett at the lowest point in your distribution system. If you have a basement this would normally be the laundry sink. If you are a one story on slab construction an outside hose bibb is normally the lowest point. Next open both the hot and cold faucetts on the bathroom lavatory sink on the highest floor of the structure that has plumbing. This will permit air to vent into the distribution piping which will aid in draining the system.

Do not worry about the water heater. Water can only flow in or out of a water heater when forced by the water pressure from the pressure source (municipal main or well pump). Once the main water shutof is closed the water in the water heater vessel is trapped inside keeping the vessel full but the water can't come out. (This is important, because if we were draining the water heater we would first need to turn off the gas or electrical supply to prevent burning out the heater vessel.) In this case we won't need to worry about the heater.

Once the water has stopped draining from the faucett open the "Waste Port" and you will only get the little amount of residual water that is standing in the vertical section above the valve. This should minimize the mess from dripping water on the floor.

Once a joint has been soldered it is nearly impossible to add additional solder to reseal the joint because you cannot get flux into the joint. The best solution is to take the joint completely apart so you can reflux the pipe before soldering.

Unsoldering a valve that is inline in a running pipe can be very frustrating because you can't move the pipe to pull it out of the joint on either side. As easy solution is to cut the pipe 4" to 6" away from the valve on the side where you need to resolder the joint, but, It is imperitive that you are sure you are on the downstream side of a valve that is turned off before cutting the pipe. AS you cut the pipe it will appear that there is some pressure on the water in the line. That is static head pressure which is caused by the physical weight of the water in the pipes above the point of the cut. The pressure is actually .433 psi for each foot vertical.

It may sound like we are making additional problems by cutting the pipe but later you will see that soldering a coupling is much easier than soldering a pipe into a valve body due to the physical mass of the valve body as opposed to that of a coupling.

You can then heat the pipe that is in the valve and pull it out of the valve. Be sure to hold the pipe with a pair of pliers because it will be very hot when it comes off the valve. As soon as you have the pipe out and while it is still hot, quickly & carefully wrap a rag around the pipe and wipe toward the open end to remove as much solder as you can. You may need to reheat the end of the pipe to remove excess solder. There will remain a thin film of solder on the pipe that will look like a thin plating, that is excellant. That light layer of solder on the pipe is called "Tinning" and will aid in resoldering the pipe into the valve, however keep in mind that the tolerance between the pipe wall and the female end of the valve is very tight so you must get all beads or buildup of solder off the pipe.

Clean the end of the pipe stub with emery cloth in the same manner as you would for a new solder joint, then clean the inside of the valve female fitting with a wire fitting brush.

Apply flux to the end of the pipe with a flux brush and apply a very light film of flux inside the valve opening. (Do not use your finger, the pipe may still be hot and in some instances dirt, debris or even the oils in your skin can get on the joint making soldering difficult).

For the next step you may need a helper because it almost requires 3 hands.

Begin by preheating the valve a bit then using a pair of pliers to hold the pipe, line it up with the valve port and continue heating the valve and the pipe until the pipe will slip into the valve. You may need a helper to lightly tap the open end of the pipe to slip it into the fitting. A word of caution, only tap lightly, the idea overcome any resistance of excess solder that may still be in the valve port, but you are not driving the pipe in, Two or three light taps while heating the pipe and valve should be enough for the pipe to slip fully into the valve port. Once it is in place, apply solder in the normal manner and wipe your joint.

I would allow that joint about 5 minutes to cool and set before making the final connection on the pipe where we cut it.

To make the final connection begin by cleaning both the open ends of the pipe thoroughly and apply flux.

Next select a pipe coupling and thoroughly clean the inside of the coupling with an ID fitting brush.

Connect both the pipes end with the coupling and begin by applying heat near the center of the coupling to preheat the coupling and both pipe ends then move the tip of your torch flame toward the top end of the coupling and concentrate the heat at the junction where the end of the coupling meets the pipe on the upper end. Continue heating and touch your solder to the junction of the pipe and the bottom end of the coupling. This is the opposite end of where you are applying the heat, but when solder flows it flows towards the heat so this will draw the solder vertically into the joint. As soon as you have the bottem end soldered remove the flame and apply solder to the top of the coupling. It should flow quickly. Wipe the joint and your are done soldering.

After all the joints have had a few mintutes to cool you can replace the cap on the "Stop & Waste valve port" and close the faucett where you drained the system but leave the lavatory faucett open to vent air out of the lines as you refill the system.

You can now open the main water valve and fill the system. As the system fills you can watch the lavatory faucett. Expect a lot of air and sputtering water until the system is full. Once you have a full normal flow of water turn the lavatory faucett off.

You will then need to open each faucett in the house to bleed off any air trapped in that line.