How to Solder Copper Pipe in a Wall

What’s up guys and welcome back to another article. In this article/video, I’ll be covering all the procedures on how to safely and correctly complete a solder in your typical home wall which might be composed of electrical wires, pipes, acoustic insulation or other miscellaneous materials. If you’ve never soldered before, this video will give you everything you need to know to be able to do it safely, and correctly with basic tools and materials that you could find at your local hardware store.

Additionally, I’ll be showing you some cool tips and tricks throughout the article/video to make it easier for you to complete the job.

Soldering in a tight spot means that you gotta take some necessary precautions that you don’t normally need to when soldering in an open space or near a concrete wall for example. A typical home wall could have electrical wires, pipes or even the wooden frame itself could catch on fire so, we’ll be going thru all of these precautions together later in the article.

Tools and materials I used in this video:
AutoCut Pipe Cutter 1/2": https://amzn.to/2Xlyq

An AutoCut Pipe Cutter 3/4: https://amzn.to/2GZFrkf

AutoCut 1/2" Ratchet Handle: https://amzn.to/2GZFrkf

AutoCut 3/4" Ratchet Handle: https://amzn.to/2GZFrkf

Pencil Torch: https://amzn.to/2GZFrkf

Handheld Torch: https://amzn.to/2GZFrkf

Fitting Wire Brush 1/2": https://amzn.to/2GZFrkf

Fitting Wire Brush 3/4": https://amzn.to/2GZFrkf

Propane gas(Blue bottle): https://amzn.to/2GZFrkf

Propene gas(Yellow bottle): https://amzn.to/2GZFrkf

Lead-free tinning flux: https://amzn.to/2GZFrkf

Lead-free flux(water soluble): https://amzn.to/2GZFrkf

Flux brushes: https://amzn.to/2GZFrkf

Lead-free solder: https://amzn.to/2GZFrkf

Flame protector: https://amzn.to/2GZFrkf

Flint striker: https://amzn.to/2GZFrkf

Abrasive pads: https://amzn.to/2GZFrkf

Utility knife: https://amzn.to/2GZFrkf

Pencil reamer: https://amzn.to/2GZFrkf

All-in-one deburring tool (blue): https://amzn.to/2GZFrkf

The first thing you’ll be needing is a good extinguisher. It’s happened to me several times that I didn’t use the necessary precautions in a tight spot and regretted it soon after, so get one that you know that’s is in good working condition. Additionally, I highly suggest getting a bucket full of water if it’s your first time soldering. Most repairs or modifications require that the main valve is closed and lines emptied before starting, depriving you from water in case of an emergency. Also, get yourself a good pair of safety glasses and gloves, you’ll be dealing with hot solder, flux which is acid and you don’t want any of these on your hands or in your eyes.

Now onto the tools and materials. So first and foremost, you’ll need a soldering torch and some fuel. Personally, when soldering in tight spots like this, I prefer getting a cheaper pencil torch as most times they are a lot slimmer and easier to maneuver. They don’t give out as much heat, but if you are only dealing with ½” or ¾” copper, these will actually do better than bigger torches in confined areas. Usually, pencil torches don’t come with a built in igniter like this, for that reason you’ll need a dedicated striker which costs around 5$. A good alternative for small pipes is this type of torch, they’re lightweight and perfect for this type of situation.

As for fuel, there’s 2 different variations when it comes to plumbing. One is your typical blue bottle propane which burns at around 3500*F and the other is Propene, also known as MAPP Gas which burns at 3600*F and usually comes in a yellow bottle. Propene is more appropriate for bigger pipes seeing it burns a bit hotter so I would suggest just sticking with normal propane.

When working with copper pipe, you absolutely need to deburr the inside of the pipe after it’s been cut, I’ll explain why when I get to the cutting step. For this, you’ll either be needing an all in one tool like this, a pencil reamer or just a sharp utility knife.

You’ll also be needing some soldering paste or flux. Soldering without flux is impossible. The flux is what keeps you pipe and fitting from oxidizing when they are being heated. There are several types of plumbing fluxes that you’ll find at your hardware store. You’ll have normal flux and tinning flux.

If this is your first time soldering, I suggest using tinning flux, it basically pre-tins your joint with a lead-free powder and reduces the chances of a leak. Normal flux which is a bit cheaper, doesn’t do this so it’s all up to you to choose what you need. One thing to make sure of is to get a lead-free and water soluble flux. Some fluxes have lead in them and aren’t water soluble so they won’t get washed away upon filling, they’ll stay in your pipes and contaminate them with lead which is not really recommended. I’ll be doing a side by side comparison of both of these later in the article.

You’ll be needing some lead-free solder as well. Most lead solders are banned from stores but it’s still a good idea to make sure of what you’re getting. What you need to look for is writing stating that it’s lead-free. If you see 50/50, that means it contains lead and for potable water system, it’s not considered code.

Other things you’ll need is a small pipe cutter, a rag to wipe any excess flux, some sandpaper or an abrasive pad to clean the pipe, a wire brush to clean the inside of the fittings and a flame protector like this. If you don’t have a flame protector, you could use a thin sheet of metal or wet rag instead, they works just the same. Everything I use in this article/video is linked here:

Alright so let’s get started. In this video, I’ll be demonstrating how to add a T on both the existing 3/4” hot and cold lines to feed a new sink in ½” piping. The first thing when doing a modification or repair is to make sure the water is closed before cutting. Like I mentioned before, if you’re closing the water from the house’s main valve, prepare yourself a bucket of water just in case, you never know what could happen when using an open flame in a confined space like this, so don’t take any chances.

Next, you’ll need to relieve any remaining pressure that’s left in the system. You could do this by opening a fixture such as a faucet at the lowest point in the house and this will ensure that there’s no pressurized water inside the pipes when cutting into them. If you’re working in the basement like I am for example, you could drill a small hole where your new fittings will be to allow for most of the water to come out seeing you’re at a lower point.

When there’s no more water coming out the pipe, use the fitting to mark where the cut needs to be made and make the cut. I find that using this type of pipe cutter is so much easier than these as they tend to snag on everything, especially in confined spaces like this. What’s cool about them is you could get a ratcheting handle to make the job a whole lot easier without sacrificing space. There’s gonna be some water left inside the pipe. Now if you can’t get your recipient to fit to catch the water, here’s a cool little trick. Get some aluminum foil and use it to divert the remaining water from the pipe into your recipient, you won’t have any water to pick up like this. What’s nice about this trick is the fact that you could form it and get into tight spots as opposed to a plastic container which can’t for example.

Now that the pipe is cut, lemme bring you in a little closer and show you the burr I talked about before. When a pipe is cut with a rotary cutter, a small burr is formed inside the pipe and needs to be removed. This lip has two negative outcomes, the first is the fact that the pipe’s inner diameter is slightly reduced, resulting in a minor flow loss, and secondly, the fact that it causes turbulence. This turbulence could eventually cause a pin hole due to the excessive erosion caused by the lip. If you don’t have these dedicated tools, just get a sharp utility knife and you’ll get the same results.

With the pipe deburred, let’s get it all cleaned up. A lot of people use these little rolls of sandpaper to clean the pipe which isn’t uncommon but I personally prefer using an abrasive pad like this, I just find it a lot easier to use. What you’re looking for is getting the end of the pipe nice and shiny.

If you half do it like this, you have the chance of having a small leak, so take your time to clean all the pipes properly. The fittings need to be cleaned as well. You could use the same abrasive pad you used for the pipes or you could get a dedicated wire brush like this. What’s fun about these wire brushes, is that you could cut the tip off using a pair of cutters or grinder and use it in a drill to make the job faster and easier. You want both of your surfaces to be rough and shiny like these right here, remember 90% of soldering is good preparation.

Now onto fluxing. The flux, which is an acid, is what keep your joint clean when heating up. Since we are dealing with acid, now’s a good time to put some gloves and eye protection on. If you try soldering without it, your solder won’t stick to the pipe and it’ll just fall off instead of going inside the fitting. Like I said in the beginning of the video, I’d do a side by side comparison of both normal flux and tinning flux. As you could see, the tinning flux will give you a better chance of getting full coverage because of the solder powder that’s in it. In any case, make sure you are getting a lead-free flux, as some do contain lead which is unwanted for potable water lines. I’ll be using some tinning flux for this demonstration.

You need to apply some to both the pipe and the fitting to make sure all the surfaces are properly covered. A big mistake that a lot of beginners make is applying too much flux, only a thin layer is needed and the reason being is that a lot of it is lost inside the pipes when it’s heated and if left there for a while it could eat up the pipe and eventually lead to problems. Here’s what a pipe with left over flux looks like, this is only after 1 week.

Now, go ahead and assemble everything together making sure the pipe is inserted all the way into the fitting and wipe any excess flux off with a rag. My pipes still have some water left in them so an old timers trick to stop the dripping, is to get a piece of white bread, roll it into a ball and stuff it down the pipe as far as you can with your finger, it’ll temporarily stop the flow while you solder and will dissolve once you turn the water back on. As you probably noticed, the joint we need to solder is pretty close the wooden stud so we’ll need to use some precautions.

If you got one of these flame protectors, get two thumb tacks and place it around the pipe in a way that anything flammable is protected. If you don’t have one, just get a wet rag and do the same thing, as long as the rag is wet it can’t catch on fire. If you’re scared of burning something, it might be better for you to solder everything in a vice and leave the tie in joints for last.

Now let’s get on with the actual soldering portion. There are 3 things to know at this stage, 1, what to heat, 2 how long to heat and 3, how much solder to use. I like using a low heat for everything in tight spots, starting with the pipe first. The reason why I do it this way, is the fact the between the fitting and pipe is a small gap, and heating the fitting can’t conduct the heat to the pipe properly because of this, so I always heat it up for a couple of seconds prior to heating the fitting. The amount of time you need to spend heating depends on the size pipes you are working with, meaning a ½” pipe will take less long to heat than a ¾” pipe. The best way to know when to apply your solder is to try it out every now and then, when it gets sucked in, that’s when it’s hot enough. However, you don’t want to wait too long as the flux’ll burn off and you’ll need to restart everything. And for the amount of solder to use it’s easy to know, just use a ½” of solder for ½” pipes and ¾” of solder for ¾” pipes. You don’t wanna use more than that, or it’ll end up in the pipe and could cause a restriction, greatly reducing flow. Something else to remember when soldering is not to heat the actual solder but the pipe itself.

I always like to start from the pipe itself for about 5-10 seconds before heating the fitting. When I heat the fitting, I start from the bottom and feed the solder from the top, anyhow, always feed opposite side of which you are heating as to not heat the solder itself. You wanna let the heat from the joint suck the solder in via capillary action (watch video to better see).

Once you’re done, you wanna let the joint cool down on its own. Never use a wet rag to accelerate the cooling process, doing this could cause micro cracking in the solder and will leak. A good visual example is if I put an ice cube in hot water. The shock caused by the difference in temperature causes the ice to crack, so always wait for it to cure on its own or the same thing will happen to the joint. Once the joint is cooled down, grab a rag and wipe the excess flux off as good measure and test your joints by turning the water back on.

If for whatever reason there’s a small leak, you’ll have to unsolder the joint, clean everything and start over to properly fix it. If you wanna see how to unsolder a fitting, go check out this video right here.