Fixing Low Hot Water Pressure Problems by Replacing Your Dielectric Union

What You Need

  • Big channel locks
  • Monkey(pipe) wrench
  • Copper tubing cutter
  • plumbers tape
  • New dielectric union (and maybe a male to male galvanized nipple)
  • Torch
  • Solder
  • Flux

Don’t let the list scare you. I was worried about the torch and solder but it is much easier than I thought, thanks to the internet. You can get solder(sweating) kits at Lowe’s for pretty cheap.

If you are a homeowner then chances are you have had some things that needed repaired, replaced, or updated somewhere along the way. Since buying a place earlier this year I have already had a handful of those projects including; fixing a leaking, wobbly dishwasher with broken racks, fixing a leaky icemaker that made little to no ice cubes, laying a subfloor in the attic, and one of the trickiest for me to figure out was extremely low hot water pressure throughout the house. Since we moved in the hot water pressure was low but it got to the point where you couldn’t really take a shower. You just had a few dribbles falling on your head which made for unnecessarily long showers.

Figuring Out The Cause of Low Hot Water Pressure

I can’t even imagine how many Bing and Google searches I did for figuring out hot water pressure problems. Over the course of a couple of months there were several search/research sessions that lasted for multiple hours trying to figure out how I could fix my hot water pressure. But almost nothing that I found seemed to be very relevant. I was able to find something about a dielectric union on a forum somewhere but, there was no end answer or pictures or anything so I was still left in the dark. I am hoping that this write-up here saves at least one person hours of searching.

Giving Up And Calling A Plumber

The water heater is probably about 12 yeas old so at one point I figured it was time to just throw in the towel and have it done professionally. I got a few quotes on full replacement and was not very happy with the prices. However, there was one helpful company that was actually straight forward with me and instead of making me pay for someone to come out and try to sell me a warranty he said he knew exactly what it was and it would be a couple hundred to fix. He didn’t tell me it was the dielectric union but he said it was the connection on one of the lines on top of the water heater. This got me searching around trying to figure out if we had a dielectric union and/or what they look like. I had little to no success on finding this information so I also searched a lot on how to replace a water heater myself.

Somewhat Blindly Digging In

One morning I had nothing to do so I decided to fix the water heater myself. Not knowing what I was replacing exactly and not having the tools to do it I just took the precautions suggested in some videos for the gas line and such and started removing things from my water heater. I successfully disconnected the exiting hot water line and discovered that it was most likely the problem. However, without a monkey wrench I was unable to remove the piece that I assumed was the core problem and I was unsure what the piece was called, making it hard to find a replacement.

Before you get started, make sure that you turn off the gas, shut off the water supply to the heater, shut the gas line going to the heater, release the pressure in your tank, and have some backup plans for if you make a watery mess.

Dielectric Union Side Shot Still Attached
Getting started, finding the cause of the low water pressure. You can see I detached the hot water line here.

At this point I am feeling pretty good about myself and thinking that it can be a pretty quick fix once I get the tools.

Dielectric Union Top View Corroded and Blocking My Hot Water
Here you can see that the dielectric union is completely done for. I don’t know how any water was making it through there.

At this point I still didn’t know that this was a dielectric union but I was pretty sure that it was the problem. So now I needed a replacement part and the tools to actually replace it. I thought I could just buy one of these things and a monkey wrench and be done with it. I found out I was wrong. After traveling to 4 different stores I ended up going to a┬álocal store to find what I needed and the guy behind the counter told me it was a dielectric union and that I had more work than I had thought. Turns out I was going to have to cut some copper pipe and learn how to solder. So this information ups my needs list to include; solder, torch, and pipe cutter. Back to work.

A Bad Dielectric Union Compared To A Good One
You can see why my hot water was having some trouble getting around my house.

Now we need to cut off the old female dielectric union. For me, I needed a male to male nipple which was about 6 inches long so I had to make sure that I figured that in when cutting. Using a small copper tubing cutter I quickly had the pipe cut and ready to solder the new dielectric female end on. The nut needs to go on the pipe before you do this so it can be screwed down. I grabbed some masking tape to get the nut out of my way.

A Bad Dielectric Union Compared To A Good One
I taped this up so that it was out of my way for soldering on the copper part of my dielectric union.

There are plenty of videos and resources to find how to sweat(solder) copper tubing so I am not going to go into details on that but here is one that I looked at before operating.

New Dielectric Union Ready to Solder
Here you can see I have screwed in my nipple and dielectric union male part to my water heater and ready to solder.

In the above picture the white parts on the nipple and dielectric union are where the plumbers tape comes into play. Read the instructions on applying the tape because it is important. I had to undo all of the screwed in parts 3 times because I screwed up the plumbers tape and had a slight leak. It is really annoying to have to undo your work because of leaks. You can see that I used this configuration to hold the dielectric union in place to do my soldering. I didn’t have an extra set of hands or any tools to hold it in place while soldering but this worked splendidly. I think I applied the solder on too heavy but it is doing the job so I will let that slide.

Dielectric Union Soldered And Ready
This is just after I soldered the dielectric union on and it is ready to tighten down.

At this point you will just untape your nut and fasten it down onto the other part of the dielectric union.


Replacing the dielectric union ended up being a much easier job than I though that it was going to be. Once you have the right tools and have done your research it isn’t too bad. So stop sitting under a shower head that is only dripping out and get the nice high pressure warm shower that you deserve. This is certainly one of the best decisions I have made. I think grand total it cost me about $50 but that is mostly on tools that I can use again. And including driving around and everything it took me about 4 hours but I bet I could do it in 1 now.