Bad mixing valve?

frankjc

Hi. I have an oil fired boiler, with the coil inside. I am not getting hot water at my sinks or showers. It's actually mildly warmer than the cold water. It has a watts 70a mixing valve. The pipe from the boiler is hot where it connects to the valve. The mix side is not. If I shut off the water to the cold connection, I get nothing at the sink. The boiler does fire up. Also the forced hot water heat does work. Does this sound like a bad mixing valve? The water in my town is terrible and known to ruin things.
Thank you.

EdTheHeaterMan

There are replacement elements for that part.
https://www.supplyhouse.com/Watts-0125129-Lead-Free-Repair-Kit-for-Watts-1-2-3-4-70A-Series-Tempering-Valve-70A-RK

Start there. If that is not fixing things you may have a coil that is loaded with calcium or other contaminants. this makes the heat transfer slower and the cold water does not pick up as much heat as it used to. This problem happens over time and is not noticed right away... Your problem sounds like the element went bad.

With bad water, you may need the coil cleaned. If it has never been done before you may need to add some valves to perform the operation. Once the valves are in place then you can DYI every few years.

You could also have a valve closed. Can you take some pictures? About 12" to 18" away from the coil and the mixing valve, and also at say 5 to 6 feet away. This may help with the diagnosis.

EBEBRATT-Ed

yes, it sounds like the mixing valve

hot_rod

I'd be tempted to replace the valve, good chance that is not a lead free version.
Shop for a valve with an ASSE 1070 listing., a true thermostatic mixing valve
Delime the coil as @EdTheHeaterMan suggested.

frankjc

It's obviously leaked, it would drip a bit at the stem and seemed to stop if I worked it back and forth.  The pipe on the top right which connects to the hot side of the valve is hot to the touch, the pipe on the left side which is the mix side is cold. The bottom is where the cold connects. I shut off the supply to that connection, and I get no water at all.

Big Ed_4

Replace it's innards , No big deal .. Cheap mixing valve

frankjc

Hopefully it would come apart. Looks pretty crusty. Last week I had to change out the supply valve for my washing machine because the hose was fused to it. Our water is terrible.
Would I have to drain the boiler and then  purge the air out when I'm done?

Jamie Hall

That does look pretty crusty. I'd just simply say the heck with it, and change it out for a true thermostatic mixing valve. You'll be a lot happier.

And no, the actual hot water in the boiler -- and the rest of the heating system -- shouldn't be disturbed in the slightest, either changing out the valve or deliming the coil. Both of those activities are on the domestic water system. No need to drain or any of that hassle.

STEVEusaPA

https://www.supplyhouse.com/Webstone-H-54443WPR-3-4-Sweat-Isolator-E-X-P-E2-Tankless-Water-Heater-Service-Valve-Kit-w-150-PSI-Pressure-Relief-Valve-Lead-Free


Pipe these in with the relief valve when you change the mixing valve. Then you’ll be able to easily flush the coil.

frankjc

So just shut off the water supply to the boiler and the cold supply going to the mixing valve?
I just realized that there is a forum for domestic hot water, couldn't see it on my phone. I guess I was supposed to post there?

Jamie Hall

More or less. You should find that there are two water supply lines to the boiler, not one. You don't need to shut off the one which is tied into the heating circuit -- but you do need to shut off the one which goes to the hot side of the mixing valve.

frankjc

Does the valve with the yellow tag on it relive the pressure inside the coil?

mattmia2

frankjc said:

Does the valve with the yellow tag on it relive the pressure inside the coil?

Yes. If you add isolation valves to the coil they must be after that valve ties in, there can be no valves between the relief valve and the coil.

It should also have a short length of pipe that brings it within 6" of the floor so if it opens it doesn't spray hot water all over the place.

frankjc

I tried to loosen in today did not want to budge. Might be time to call a professional.

frankjc

It it ok to apply heat to get it apart?

mattmia2

If you have a new part. Heat will most likely destroy any seals in the old one.

STEVEusaPA

Just cut it and repipe it. Trying to get that off with heat and a new one on the same pipe is nearly impossible-especially for a beginner.

frankjc

I think I will just pay someone to do it. I have no experience sweating pipes, I am not sure this is the right situation to learn on. I have always wanted to learn though. I will give it one more try without heating it, then I am done.
Thanks everyone.
i appreciate the input.

Larry Weingarten

Hi, I’ve worked on lots of these . Try two pipe wrenches. Use one to hold the body and one just on that cap. Squeeze between the wrenches.

Yours, Larry

Intplm.

@frankjc what you have pictured is not a mixing valve but what is called a tempering valve.
They are of the old technology grind and are no longer installed in "most" newer installations. They have a very high failure rate and do not take well to rebuilds.

If you are considering going to all the trouble of changing the element in your current tempering valve. Why not just change the entire valve to a thermostatic mixing valve?

The one pictured below is just one example of a thermostatic mixing valve that will serve you well for many years to come. A tempering valve will more then likely not.

Install one of these as pictured below. It will serve you well with better and safer temperatures.

frankjc

I may go with the same part that is on there, for simplicity sake. Also because of my limited plumbing abilities. The less new connections the better.
If I do it myself, I have a few questions. (I am an overthinker)
1: Can I heat the joints and reuse the old fittings?
2: If so, do I have to get every bit of solder off the pipes and fittings?
3: Will it cause damage to the valve, if I apply heat to it when soldering? Or do I heat the pipes instead?
4: Is tinning solder better?

hot_rod

1st time soldering? Might want to get some tube and fittings and practice first. Working on disassembly and reuse will be a tough first go
First all the water needs to be evacuated somehow, a wet vac or air compressor may be needed.

I'd highly recommend installing a valve better suited for that application, I doubt that is a code approved valve, needs to have ASSE listings on it. Yes, some repiping will be needed.

mattmia2

I would use something like this version with built in unions, especially if it were my first time soldering:
https://www.supplyhouse.com/Taco-5003-C3-G-3-4-Sweat-Union-5003-Mixing-Valve-w-Gauge-Low-Lead?gclid=EAIaIQobChMI0NXb9-nw6wIVBdvACh1ArQ5zEAQYASABEgIETPD_BwE

The outlet gauge is convenient, but you might do less re-piping with the version without it.

hot_rod

Or... a fast responding valve, fails cold, built specifically for tankless coils and heaters. Rent a press tool for 1/2 day and you have a easy, appropriate solderless replacement.

frankjc

So it's not as simple as heating it with a torch, sanding the old solder off the pipes and sweating it back together?
Also it does sound like a good idea to get some parts to practice. It is a skill that I've always wished to have.

mattmia2

Desoldering a fitting and putting a new pipe in it or vice versa is the masters to phd level of soldering skills. You need some practice to not overheat and burn everything and to tap/wipe/brush the molten solder off so it will fit back together with the new parts.

The easier and more standard way is to cut it out in straight sections of pipe and fit it back together with couplers and new pipe sections and fittings.

SuperTech

I just wanted to also recommend ditching any thoughts on rebuilding that Watts valve. The difference between that valve and the Caleffi thermostatic valve that Hot Rod mentioned is like comparing a Model T to a new Corvette.  I recently installed one myself and have been very happy with it. 

Soldering is easy if you make sure to clean the pipes and fittings properly and make sure that everything is dry before starting. Using a press tool is simple if you can get one. 

mattmia2

I was just suggesting an integral union type valve, not necessarily that specific valve so that they won't melt that valve and if they screw the soldering up badly enough they can get a new union half.

frankjc

I'm torn between wanting to do it myself, and learn a new skill at the same time, and just getting it done by someone who knows how to do it. 
I had a friend who was supposed to call a friend to see if he would do it for me, I would have gladly paid him for his time, but I haven't heard back.
I just need some hot water....
I may go to the store, buy some supplies and sweat a couple of practice joints and see how it goes.

Larry Weingarten

Hi @frankjc , I agree with the others about replacing the valve. The reason I got to work on so many is because they failed. Seems it is time for you to play with soldering a bit and gain that skill. Try making up some joints and then hook them up to water and see if they leak! FYI, the flux I like is called C-Flux. It turns dark just as the temperature is right for adding solder. You can find other threads here on soldering technique and preferences. There are lots of ways to do it successfully

Yours, Larry

SuperTech

@frankjc I believe that you can do it! Go for it, feeling proud of job well done and learning a new skill is well worth it.  And its always great to know that in the process of performing a repair you have improved your boiler at the same time. With a little practice I'm sure that you will be able to replace that beat up old tempering valve with a superior modern thermostatic valve. 

frankjc

So I got it loosened, carefully with vice grips. I'm probably going to pick up the repair kit. I think for my skill level that is the best bet. 
If I connect a hose to that relief valve with the yellow tag on it, will that drain the water out of the coil and make it safe for me to work on? 

STEVEusaPA

There’s not much water in the coil. If the domestic supply is off you can just open the relief valve and drain into the bucket.
The only problem is it may not seat again. Relief valves should be tested annually. You should probably replace it anyway, with a proper replacement and pipe the discharge down to within 6” of the floor.
When you get the tempering valve apart, some water will probably drain out of that too.

GroundUp

I'd be willing to bet you're not going to like the outcome of a rebuild on that Watts tempering valve. It's very likely that it'll fail cold and you'll end up replacing it anyway. There's a reason those valves are $35, they're garbage

frankjc

Larry Weingarten said:

Hi, I’ve worked on lots of these . Try two pipe wrenches. Use one to hold the body and one just on that cap. Squeeze between the wrenches. Yours, Larry

What is the dissembly process? I have the replacement part. Thanks.

Larry Weingarten

Hi @frankjc , Once you have the cap off, (better have water off as well!) the innards should just lift out with the cap. There is a spring that the new cartridge will fit into, so it's held in place while putting it back together. When you have it apart, be sure to clean out any scale you can see and give it a flush so debris doesn't mess things up. Even though it's an O ring seal, I like to put a turn or two of teflon on the threads so it will come apart easily next time. As long as you have it apart, it's good to exercise the knob on top so it can travel it's full range, while you can see and clean the internal parts.

I've run across these primarily on old solar thermal systems and they failed so regularly that people were wanting to rip out the solar. On the next round, you would probably be better served by going with a modern valve. Just sayin'

Yours, Larry

frankjc

I replaced the part, cleaned out the inside best I could, still same problem. The strange thing, it won't fire up to make hot water unless I turn the lo control on the aquastat past 180. When I was poking around the other night that happened too. Wasn't sure what to make of it.

frankjc

Also, the pipe on the left which goes to the hot side of the valve is hot at the bottom, but much hotter at the top, above the connection in the middle. What is that connection?

mattmia2

That's just a union. it just is a fitting that allows two pipes to be screwed together without either turning. It means the valve still isn't flowing(or something somewhere else in the system). You could pull the guts out and turn the hot water on slowly and see if water flows out of the valve body(with a bucket or something under it). Maybe you just need to turn the knob more toward hotter?

Can you take another picture of the front of the tankless coil that shows how that is plumbed?

frankjc

Knob is turned all the way hot. Always has been. I'm done playing with it for today. I was thinking about taking the thermostat completely out of the valve to see what happens. I'm really tempted to just get an electric on demand hot water heater. My hot water has never been much good anyways.

mattmia2

See the comment about people wanting to rip out their solar because of the crappy valve you have. I guess the tankless is rather inefficient so the electric could cost less to run.