Cleaning/Descaling Indirect Water Heater-Or is it too rusty?
Any tips on cleaning the inside of an indirect water heater? I've seen mention of using vinegar, or some mentions of commercial descaling products that are use in tankless water heaters.
Working with a Weil Mclain Gold 50 gallon indirect water heater that's connected to a Weil Mclain boiler. This is an older Triangle Tube Weil Mclain Gold, not the newer style so there is no actual drain. If the water sits in the tank without constant use, it turns yellow/rusty colored.
This water heater sat unused for about a year from what I understand. Everything seems to be working as it should, no actual leaks, just that the water has a rusty color if it sits unused. I already pulled the inlet pipe and did manual flush with a piece of 1/2 Pex to the very bottom of the tank. I also pumped the water out from the bottom multiple times, so I am certain this tank has been completely emptied and refilled multiple times.
In this last test, the water heater sat full for about 2 months unused, and the first gallon of water came out dark rusty colored. The rest of the 40+ Gallons has a yellow color to it, so the entire holding tank is being effected. This tank will not be sitting unused any longer as there will be people in the house soon, but, I still want to try to get this thing running clear before I decide if I need to just replace it completely.
From what I can tell this issue is in the tank, tank walls, or possibly the coil surface inside the tank from the boiler. The plumbing coming in, and going out is nearly all new, so no components to cause rusting. The pressure in the boiler is staying the same (Not rising, or falling) so it seems the boiler supply/return isn't damaged.
I may get an inspection camera to get a real good look around. Trying not to replace this unit just yet since the entire boiler setup will be replaced in the next few years.
Could the holding tank simply be too rusted from sitting unused/possibly empty for so long? This particular water tank is supposed to be stainless, but I know stainless still rusts.
Any tips to help me get this thing cleaned inside, or any other ideas?
Comments
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Any time water sits in a steel or stainless steel tank for a long time undisturbed there is going to be some corrosion ("rusting"). Can't help it. This is what, I expect, you are seeing. Due to natural convection in the tank the colouration will spread through the entire volume of water. Can't help that, either.
Now… how to get rid of it. Well, multiple drain and fill cycles will certainly help to reduce the problem. However, if you have access, a pressure washer with a nozzle set at right angles, slowly rotated around the entire wall of the tank (with the tank empty) and even more slowly lowered to the bottom will speed up the cleaning. A lot…
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England1 -
Thanks for the idea of power washing.
I attempted to drain and refill it with a normal hose pressure on the inlet side of the tank with a piece of 1/2" pex to the bottom that I used to fill and them pump it out. I managed to get some sediment and crud in the first pump out but all seemed fine after that. This house hasn't been lived in regularly, so the water has been sitting so I don't have a good gauge of what it does day to day and if it continues to be rusty or not, or if it clears once used steadily.I like the power wash idea, but getting it into the small sized nipple is going to be a challenge. Guess I need to get creative and think of a way to either get some water in there under pressure, or, possibly some type of brush or something I can move around to help get the crud off the interior. If the rust is coming from the coil, I probably won't have much luck.
I called the manufacturer and they said if its not leaking, and I don't find evidence of a broken coil, chances are I should be able to do flushes to get it back clean and they were pretty confident in that.
Time to get a small camera in there so I can see what I'm dealing with.
If anyone else has any experience or ideas what I can try in this situation, I'm all ears.
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From what I remember about that Triangle Tube tank, there are no access openings for cleaning. There is an inner Stainless Steel tank that is filled with potable water and an outer tank that has the boiler water in it. (no heat exchanger coil). The only access to the inner tank is through the ¾” male, hot and cold water openings that are welded to the inner tank and welded through the outer tank. Not much space for a spray wash nozzle at a 90° angle to fit in those openings. The cold inlet has a plastic dip tube that runs to about 4" from the bottom. So no real access through that opening.
Since that tank is over 30 years old, you may want to think about replacing that indirect with something compatible with your new future system.
The center opening is for a vent to purge Boiler Water from the top of the tank. No potable water access there.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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A wet vac with a long skinny wand
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream
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I doubt it is worth the effort to attempt any sort of cleaning. From what you described the integrity of the tank itself has been compromised and it is probably not going to last much longer.
This is like trying to buff and wax a car with a rotten frame.
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Hi, If you could prevent further rusting, than flushing would likely be sufficient to give you clear water. If there is a way to install a powered anode, that would stop the rusting. I'd also make sure the water has little or no salt in it.
Yours, Larry
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As Ed mentioned that may be a tank in tank design. The inner tank is stainless. Not many connections into that tank to add an anode?
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
Is there no drain port? At this point, I would try adding a couple of gallons of vinegar and letting it sit a day or two before cleaning again. It can't hurt and it probably will help loosen the rust and lime scale that's settled at the bottom of the tank.
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This is a tough problem. The inner tank wall is corrugated so there’s plenty of surface area there in addition to what might be a lot of sediment on the bottom. It sounds like you’re doing a good job flushing. I’d follow the manufacturer’s advice or replace the tank. What’s your water quality like? Is it high in iron? What happens if you use it everyday in a normal way? It might eventually clear up and be fine. This sediment is probably in all the piping too.
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Thanks Ed, you are spot on with your info. Triange Tube, no access other than the 2 nipples. I changed out the dip tube a few months back. Thanks for the diagram, I knew there was an internal storage tank, but my mind had me thinking there may be a coil of some type that also flowed inside the hold tank, so its good to know its just a bit empty open space and in theory there is no actual coil to get extra build up on, just the walls of the entire steel tank. That diagram was helpful to visualize it exactly.
A few months back I popped the cold water inlet off, and I used a piece of 1/2 Pex to reach the bottom and pump water out, and flush it in. At that time I got a bunch of sediment out and things were looking pretty clear if water was used instantly, but if it sat for days/weeks it would rust. This time the water sat for a good 2+ months so the entire holding tank is showing light yellow, where the first gallon was dark rusty water. Your mention of corrugated walls and lots of surface area to hold rust is sounding more and more like the case here.
Thanks to EVERYONE else for your feedback, its all helpful at all angles. From the comments saying to just get a new tank, to others saying there's possibly a chance and to keep with the cleaning.
I think my game plan now is going to be to do another flush and cleaning as one last ditch effort, before I hack this thing out and replace with a similar indirect. A few more hours worth then I call it quits. Some things i'm going to go at it with:1.) My inspection borescope camera didn't show much, but its old and I need to do an inspection on the main line at this property, so I may invest in something better and use it for this purpose as well, just to see what I'm dealing with inside.
2.) Flush with my 1/2" pex from the bottom of the tank, and then pump it out. Do that a few times and then fill it up and access. I have the pex setup ready to go, and a power pump so this isn't very hard to do. The hard part is knowing if the water will yellow after time, so I'll have to do this, then wait and see what the next days/weeks bring3.) I have a power washer and see they sell those main line drain unclogging heads. Those unfortunately may not fit into the nipple after all, but its worth exploring. If I can't get something to fit in the nipple, this idea goes bust.
4.) I'm considering dropping some vinegar inside and letting it sit a few days. I'm assuming the steel walls are pretty thick so it may be worth a shot. Debating on dilution since I have high acidity vinegar I can dilute down to whatever percentage I want. I could rig up my pump to circulate the water from the inlet to outlet and let it run a few hours to break up any crud.
5.) If I can figure out some type of brush to fit into the nipple I may take a chance at scrubbing the walls best I can reach them.
Lots of chances to give this thing life. The rep at the manufacturer was adamant the yellowing should stop after flushing and said if there are no visual external leaks, flush and send it working till it does leak. So that gives me some hope in salvaging it and getting a few more years out of it. I've come to terms with the fact that this may just be a remove and replace job though, so I'm already shopping for a replacement.An exact replacement Triangle Tube Indirect same gallonage is about $1600 delivered. So if I can't get it figured out in about 2-3 hours of efforts, its off to the scrap yard and in with something new.
Thanks again everyone. Any last ideas, send them my way.0 -
Just to add one thing that may help with cleaning.
Most of those tank (50 gallon and above?) had a third connection in between the hot and cold. You could put a relief valve there and also use for a re-circulation line. I believe they even included an extra dip tube for the third connection.
If you have the third connection, maybe set up the pex and pump on the cold line and make a clean out tool with a piece of 1/2" or 3/8 OD copper(bent at the end) using the third connection. Wash and pump out at the same time.
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I really appreciate your effort and determination to get this tank cleaned up and get the most you can out of it. I hope you succeed. The only other things I can think of is make sure you don't have any ferrous fittings or pipe anywhere to the tank. I have seen that mistake made twice recently. My concern is that once any rust or degradation of the tank starts it will continue no matter how well you get it cleaned.
It's quite possible that particular indirect is not the best choice for the water in your area. Before you get another indirect tank just like it I would have your water checked out and then choose a tank that is the least prone to issues with the quality of water in your area. A glass or stone lined indirect might be better than a stainless one in your area.
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It is probably all the minerals in the water that have collected in there. I would use a good amount of citric or hydrochloric acid to re-dissolve them then flush it out. If there is significant sediment on the bottom which there could be several inches or more, you would have to break it up and suck it out. There is equipment to do this for commercial tanks but it could cost more than an new tank.
Make sure there is no steel piping from the tank. A single steel dielectric union can make a big slug of rusty water it is sitting for a while.
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Any idea the ratio or concentration of citric acid that would be ideal in this case? Google says 5%-7%, up to 10% but not sure that's reasonable, and assuming water temp may affect it.
Good point on the possibility that the sediment on the bottom could be caked. I'm going to drop an inspection camera inside and see what I'm dealing with.0 -
Generally minerals and heavy deposits sink and settle on the bottom of the tank. In an indirect like that is doesn't cause a lot of heat transfer penality. As it does in a tank with a burner below.
You can get hot water rated cartridge filters that you could install on the HW outlet to catch any deposits.
if it is rusty water, that is coming into the tank from the supply, stainless tanks don't rust, oo put a sediment/oder filter on the cold side.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
Good point on the heat transfer since it doesn't have the burner at the bottom like a natural gas setup.
I was thinking about that, putting some type of general sediment filter on the HW output, I guess that's an idea if this issue only creeps up when the water heater sits dormant.
The rusty water is definitely from within the tank, as I'm running the cold water beside it and comparing it in white buckets as my baseline of color. The place has nearly all new Pex, so the tank itself seems to be the culprit. It did sit unused, uncertain if it was full or empty during that time, so it may just be rust from that period.
I'm getting into it tonight and over the weekend, I'll report back any findings.
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Try putting some cold water in a plastic bottle with a plastic cap and letting it sit a while. It could be iron in the water that changes oxidation states from something soluble to insoluble over time.
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If you're getting a slug of a gallon or so of very dark colored water and it almost immediately gets much clearer that would point more to a fitting in the piping than the tank itself. The water comes off the top of the tank so it isn't like the outlet is sitting in some sediment in the bottom of the tank that is flushed out in the first gallon. Are you sure the inlet and outlet are piped to the proper tapings so that the dip tube is connected to the inlet?
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You can get a piece of half inch PEX in there? OK — here's a cleaning wand for you. Take a piece of half inch PEX and plug one end. Doesn't matter how, but it must be firm. Then just above the plug drill holes around the pipe — say four of them, 1/8 inch. Don't worry about burrs. Connect the other end to a pressure pump — as much pressure as the contraption will take — and lower it in slowly rotating a quarter turn back and forth as you go down.
Instant lateral pressure washer nozzle. Red neck style.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
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With that tank, the outer shell is plain steel, under boiler pressure. It could be a pin hole is allowing the boiler water in to the inner tank? But generally the boiler pressure goes up in that case, and the relief valve seeps. Really no other way to get rust in a stainless tank, it must be coming in from another source..
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
The first gallon or so of water is dark after the line is cleared (Newer pex lines). So its definitely whatever is sitting at the top of the tank also. I haven't looked at the hot water nipple yet (Stainless), but the cold water inlet nipple definitely is yellowing/rust/darker colored. I took a small brush to it and tried to clear it up. The coloring didn't seem to change, but at least if there is something that was on it, its no longer on it. I'm going to do the same with the hot side and check the dielectric union there. I swapped the dip tube last year, don't think there is also one on the hot side, but I may as well check at this rate.
Great idea! I tried to hook my wet/dry vacuum to a 1/2 piece of pex, but for whatever reason it couldn't pull strong enough. I got some water up, but it was a struggle. I may try again with a slightly smaller vacuum. I ordered a sewer jetter powerwasher accesory set that has different nozzles and a smaller sized tube that I'm almost certain is going to fit into the tank, so if that doesn't cut it, I may try your homemade pex tube idea.
That was my initial thought too, that something is coming over from the boiler water since that tends to get dark as I added radiators to the system. However, the pressure is dead set at around 10-11psi cold, and goes up to about 15-16psi or so while heating, and returns back to 10-11 once its totally cold again. I'm still not ruling this one out, but, I have none of those symptoms you mentioned so for now I'll table this one.
Update:
So I went exploring last night with a borescope, and felt like I was exploring the surface of Mars. From what I can see, it looks like there is a bit of a film on the tank in most areas across the entire thing, yellowish colored, but I can see it has been wiped away everywhere my pex tube rubbed while I was trying to move it all around. Some bits of the old blue plastic tip tube that broke. Then, a bunch of very small tiny pieces of rusty metal on the bottom, and then small pile/chunk of rust. Almost looks like something small made its way into the tank and is rusting down there. Maybe it was an old dielectric part that somehow fell in, or something like that.
An attempt to hook my wet/dry vac up didn't work all that well with some water in the tank. So I may go at it again with some other vacuum. Almost like the 1/2" tube is too restrictive so the vacuum can't pull the entire height to get the water or stuff up and out. I may try again with a different vacuum.I did some research and it seems a sewer jetter setup that goes on a power washer may actually fit down the nipple. It comes with an assortment of nozzles that shoot in all different directions, so I think this may do the best possible job of attempting to clean the inside up. Then I can just keep filling and pumping the water out until all that muck is gone.
As for the chunks of rust/old metal parts, and the old dip tube, I don't think there is any hope of getting any of that out, so it may just have to live inside. That chunk of rust may be the culprit here sadly.
I'm giving the power wash a go over the weekend, and then am hooking it all back up and getting it up to temp with hopes it runs clear. Now that I know this is mostly just some rust from some metal part down there, I may simply install a hot water in-line filter IF it won't drop the water pressure too much for showering, and call it a day until I'm ready to upgrade the entire system in the future. Even if these efforts give me 2-3 more years, it would have been worth it so the money spent can go towards whatever new system I end up installing.
Hope you all don't mind all the fine details, but I figure I may as well take you all along for the ride. Thanks again to everyone for the ideas, they've all been helpful and have pretty much gotten me to where I am at now.
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Don't use a dielectric union or steel nipples, that is where your slug of rust is coming from. Use a brass nipple. Are you sure the nipple you think is stainless isn't just galvanized?
Loop the pex up and down to the level of the vacuum so once the pex is filled the vac isn't lifting the water. Might have to prime it somehow.
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Hi, Long ago I designed and built tools for vacuuming the sediment out of tanks. Motive power came from a bilge pump. This is a positive displacement pump that is self priming. Water and sediment would flow up a "wand" that was inserted into the tank. Then into a filter and then to the pump and water back into the tank. Maybe you can use some of that thinking to solve your problem? 🤔
Yours, Larry
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You should show a pic of the Muck Vac for folks to see how it was built?
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
Here it is. 😊
Yours, Larry
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These nipples are welded directly into the stainless steel tank. I had an issue on one of the threads where I was trying to rework it and turns out they are welded in, so I'm stuck with the stainless.
I tied the vacuum from the basement ceiling and it helped, but not enough to actually get more than a little water, no actual bits could make it up, so I gave up. I am thinking I may use stainless corrugated type water supply tubes, then transition over to pex with a brass fitting. Stainless and Brass are ok when it comes to dielectric, right?
GENIUS contraption and design, nice work! I have an electric water pump I am using to pump it dry during flushes, but I doubt it could pass much throw its vein/impeller so I won't be able to successfully do that. I use an extractor to drain motor oil on some vehicles, so from the drawing I totally get the concept, but I don't think I'll be able to go through the work of building one just for this 1 water heater. If I was encountering them regularly, this would certainly be an invaluable tool to have around. Maybe I'll have a stroke of luck and have some parts around that I can concoct something to vacuum the bottom.Time to get cranking on power cleaning over the weekend, wish me luck!
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Wow @Larry Weingarten, that guy looks just like you!
Long hair, bearded, 20 something, from the 1970s. Nice Disco Shirt!
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Stainless and brass are fine. If there is a dielectric union in there, those are made of galvanized steel and have left a little slug of rust with the first draw of water after sitting a while whenever I have used them. You could use a brass or copper union or just connect a pex adapter right to the tank with brass or stainless fittings if needed.
If I were planning on replacing the tank soon I would be even less concerned about galvanic corrosion.
The various iron oxides are more dense than water so they will settle to the bottom of the tank after sitting for a while, I really highly doubt the stuff you see at the bottom of the tank is what you're getting in your water.
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Good points all around. With water heater connections to the nipples, are you stubbing off with copper or a corrugated style tubing before transitioning over to brass/pex? I know some codes used to require that, but maybe that was only on natural gas? I was considering using a few stainless corrugated lines and reworking all the plumbing/valves in/out of the water heater so when I do a replacement, all I have to do is unscrew the corrugated line ends off the nipples and swap the new water heater in. That ideal? Or should I first stub up a few feet with copper, then go over to pex?
You could certainly be right on the dielectric slug running the water rusty, especially the first gallon since it may be siting right there at the top. This tank ended up turning almost all yellow though, so I'm guessing that was probably a combination of everything and since it sat for a good 3+ months unused since I last flushed it. If there was a dip tube wrongly installed on the hot side, that could certainly be adding to the issue pulling from the bottom, but my guess is that is probably not the case.0 -
Hi @EdTheHeaterMan , Actually the shirt is the same chambray blue work shirt I have on now. I make 'em last a long time. 😏
About hooking up the tank, I vote for corrugated stainless flex lines with true dielectrics in the ends. This allows for simple hookup when you get a new tank, and doesn't work-harden like copper. I would re-tighten the nuts about six months after initial installation as the washers can shrink with heat.
Yours, Larry
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Thanks Larry. What do you suggest as a true Dielectric end? Can I go from the stainless nipple off the tank, stainless corrugated flex line, and then go directly to a threaded brass NPT to Pex adapter? Almost sure Stainless and Brass may cause some galvanic corrosion. Would it make sense to just use a Stainless 3/4" NPT to 3/4" Pex adapter and eliminate brass or a separate dielectric in the scenario completely?
I see SupplyHouse sells this Stainless adapter that may do the trick and then the entire setup stays stainless from the nipple, to the flex tubing, to the pex adapter.
The Stainless Flex tubes I'm using say they have integrated dielectric sleeves to help with dissimilar metals?These are the stainless corrugated tubes I'll use:
https://www.supplyhouse.com/Brasscraft-SWB00-24N-3-4-ProCoat-Flexible-Corrugated-Stainless-Steel-Water-Heater-Connector-24-Length
Should I grab one of these adapters?
https://www.supplyhouse.com/Boshart-SSPEX-MA07-3-4-PEX-x-3-4-NPT-Stainless-Steel-Male-Adapter
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Hi, Look for flex connectors that look like this: You want them to have the plastic sleeve between tube and nut. That along with the rubber washer inside makes them real dielectrics. If you took an ohm meter you would find no continuity between nut and tube. This sort of flex along with nearly any other brass or stainless fittings will work. 😊
Yours, Larry
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Very helpful, thanks for that photo and the extra info. And if I used that stainless adapter and went right to the pex that in theory should be fine as well, right? Since its going stainless nipple, to stainless tube, to stainless pex adapter.
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