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 local 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.

  • Darryl Iorio

    Your old dielectric union looks totally worn out and rusted. It’s a good thing that you learned that this was the root cause for the low hot water pressure of your heater and that you were able to it all on your own. I bet it saved you a lot of money too.

    Darryl Iorio

    • yeah I was quoted $275 to have it fixed or $1,000+ for a new water heater

  • Phil Holloway

    What is the silver bolt for that is taped to the copper pipe?????

    • That is part of the dielectric union that you have to slide on before sweating the pipe

      • Jack Bravatto

        this may be a dumb question but why couldn’t you just replace the corroded part of the dielectric union so you didn’t have to cut anything. or is the whole union shot once it corrodes???

        • I am betting you could just replace the corroded part. However, at least what I bought, it was a package deal and the few extra minutes it took to cut and solder I don’t think was too big of a deal. That said, logically (i’m no pro), I don’t see a reason you couldn’t just change the corroded part other than for mine the non corroded part was the part with the gasket on it.

  • Thanks for the help..

  • Ims

    can you post the final picture. And why did you have to add a pipe extension. Couldn’t you simply replace the dielectric union. And why did you cut the pipe. Apologies if I am missing something here.

    • I cut the pipe because that is how you install that end of the dielectric union (see picture with tape). The pipe “extension” is simply a male to male connector be cause my dielectric union and water heater were both female

  • Michael

    Leave the guy alone with “Why did you do that?”. He fixed it and it works. You did good bud.
    From a retired union pipefitter.

    • Thanks Michael. It took me a lot longer than I wanted it to, but ultimately it worked out ok. 1.5 years later and the water heater is still running like a champ. So it at least put off the $1k or so we will eventually have to spend for a new one. Maybe i’ll even try to to tackle that myself to save some $$$ but I dunno…

  • Avalon Morley

    Very interesting post, and thanks for documenting all that. I don’t suppose you live anywhere near Dallas, TX, and want to be hired to do the same job on my heater? I’m only sort of kidding. If I could, I’d try to do this myself, but there are reasons I can’t right now; also, I’m not 100% sure this is my problem, though I think so, as the pressure has gone considerably down on the hot water throughout the house (I wonder if it signifies anything, that it’s come on rather suddenly–though maybe it had been progressing, but only got to a point where I noticed it recently). Anyway, this certainly seems the most likely problem (does anyone know of any other possible scenarios?), and I really would like to find some very handy person who could do a competent job of this, but doesn’t charge as much as the plumbers around here do. Anyway, thanks!

    • Haha, sorry it would cost more for me to get to Dallas, TX than a plumber would charge probably.

      As for it coming on sudden I could see it maybe being clogged somewhere on the hot side coming out of the water heater by maybe a chunk of debris (build up or perhaps rust depending on age and water quality in the area).

      Ours was slow but somewhat tolerable for the first 6-8 months we lived here and then it seemed to almost stop (not exactly suddenly but a quick progression from bad to terrible).

      It really was an easy job and I was able to remove the dielectric union without any thing but a monkey wrench and channel locks basically (see pictures 1 and 2). So you could technically just take the old one off to see If it is clogged before you actually get into the real work.

      • Avalon Morley

        Just found the reply, so thanks. Very fortunately, it turned out to be only that the shut-off mechanism (that has a sensor to shut off the flow of water into the heater when it senses moisture down at the heater’s base, which it does from time to time when there is no moisture at all) had somehow gotten stuck at half-closed. I had tried more than once pushing the green “open” button, which did nothing because this mechanism was convinced that it WAS open (and the indicator light was blinking in the ‘all’s well’ pattern). A friend who knows a bit about these things came to help and tried pushing the red “shut off” button; it made the noise that usually makes, but only for about half the time it usually lasts. Then, once we were sure the hot water was shut off completely, he pushed the green button, which made its customary ‘whoosh,’ for the normal length, and then the water pressure was back to full strength. Hooray for easy fixes! Thanks again.

        • Awesome, glad you got it figured out. Also your comment may help another soul out there with similar problems.

  • Gter

    Thanks for sharing your experience and detailing it with great photos. I was away from home for a couple weeks and came home to just a trickle coming out in the shower when I turned on the hot water.

    I was pretty surprised when I loosened the connection and took a look at the problem. I’m including a photo of part of what I saw.

    With a $12.99 part and the tools you recommended–as well as a brush-up on soldering class from metal shop in high school–I was able to fix something I thought was going to require a whole new water heater in less than an hour (once I had all the parts).

    • AWESOME. Glad you got it done quickly. Glad my hours of research + realizing the tools/parts I needed helped save someone some time.

  • Larry Salberg

    Read this post with interest, having lost our hot water pressure and finding little/no help from the average plumber phone call. After identifying this, a called one plumber who came out and did a quick fix by reaming out the cold water intake with a coat hanger (because tearing into the piping would take time he couldn’t spare in the quick inspection visit. Voila! Hot water returned!

    The question I have is whether you ever replaced your hot water heater sacrificial anode? It’s the device designed specifically to corrode to ensure things like the couplings you showed in this post do NOT ever get corroded. I read, with horror, that a homeowner SHOULD inspect the anode on an annual basis, replacing the (relatively inexpensive) anode whenever it gets too far gone (i.e. corroded). Our heater is eight years old and I know we’ve never done that, nor have any of our neighbors, who are now experiencing similar problems.

    I located an an excellent white paper by Rheem/Ruud on cathodic protection of hot water heaters that discusses how this works and how to inspect/replace the anode. Here’s the URL:

    Since your heater is (was) 12 years old when you wrote this, I’m wondering what its present status is? The plumber who fixed our hot water said that, unless you’ve checked your anode on a fairly regular basis (not necessarily annually, he said), it may be problematic to attempt to replace it. In fact, he said that, for a unit as old as our 8-year old heater, he would not even attempt it himself since he has ended up damaging a heater to the point it had to be replaced immediately.
    Based on the external corrosion we have on the hot & cold water connection couplings plus the internal blockage, he said we may have another year or two before ours fails catastrophically (translation: starts leaking all over the place). So, he recommended planning to replace it. Since he doesn’t install heaters anymore, I’m thinking that’s a fairly professional & unbiased recommendation based on many years of experience.
    Just wondering if you’ve ever inspected or replaced your anode.
    Thanks again for a great write-up!

    • Hey, thanks for the post and extra info. I will read the pdf or at least skim when I get some time but here is an update. Our heater is now 14 (almost 15 years old) and works perfectly fine atm. The $50ish fix I did 2 years ago saved buying a new heater by at least 2 years and counting.
      I am not a plumber and don’t have all the info, but from my research the dielectric union (part I replaced) is also meant to take the corrosion instead of your pipes. Perhaps what you describe and the dielectric union work in tandem to help the longevity of a water heater, but I do not know.
      Thanks again

  • Pat

    Thank you for your post. And the pictures were very useful. Lost all hot water pressure a week ago and this weekend tackled the job. Because if your post and the very detailed explanation I was able to fix the clogged pipes in just a matter of a couple hours. I did also replace the steel nipples in the top of the water heater because they were clogged too. After a little pipe cutting to fit everything back together I had no leaks. Lots of hot water. And a happy wife. Your post was the best I saw and you saved me over 500 bucks by not buying a new tank. Thanks very much. Pat.

    • Glad it helped. We have been living here for 3 years now and the water heater that I was told would need/should be replaced is still chugging along. I know i’ll have to replace it some day, but I at least set that $1k bill back by several years.