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What are modern procedures to prevent carbonate deposits over the coil of indirect DHWT ?

Dear Members ,

To begin with , i would like to thank the manager of this Website for providing us with much more informative lessons on whatever belongs to this vital industry . Before I posted this topic , I was searching through former posts about the above topic and I learnt some thing practical . Indeed, my current project and enthusiasm for learning encourage me to share these photographs and to hear your take on this particular problem which always takes attentions of many installers and engineers to find a practical and affordable remedy for residential application. Thank you for taking the time to consider my post and do appreciate your support ,as always.


This boiler room has been installed for 12 years . A 1200 liters galvanized indirect domestic hot water tank has got dismantled last week for descaling the coil and removing mineral deposits from inside of it .This project is our last traditional boiler room that we installed ,and have maintained it up to now . There are two sectional boilers for Radiant floor heating system and swimming pool , spa ,and indirect domestic hot water tank respectively .

As scaling the coil of the tank is quite prevalent in boiler rooms in here , we often descale them between 7 to 10 years after their installation when their make up lines is city water ( Tehran city water which supplies by water organization ).In other words, City water in terms of minerals are acceptable medically .For instance, Its PH is 7.9 , TDS 150 ppm .However, Galvanized tanks are still good choice for providing plenty of hot water for apartments buildings without occupants experience cold sandwich phenomenon . Thus, I would like to request for further information on how to protect the coil of the tank against mineral deposits and how modern tank type put an end to this problem ?


Once more, thank you for your time and help,



Also, congratulate you all for your country accomplishment in Rio Olympic .


I look forward to hearing from you ,



Yours Sincerely,

Roohollah














Comments

  • hot_rod
    hot_rod Member Posts: 14,753
    Softening the water would help, do you ever apply ion exchange type water softener.
    Any idea how hard the water in, generally expressed as ppm, or grains of hardness?

    A simple drop titration tester is best for checking hardness.

    While not idea looking, I have seen tube bundles with so much build up that they look like a block of stone.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Roohollah
  • Roohollah
    Roohollah Member Posts: 118
    You are right .Sir, There was so much build up over the tube bundles ,and inside of the tank as well . As you shall see, the deposits in side of the tank look like a wormy shape .

    With regards to Ion exchanger , I would like to say that we usually apply it to those projects where City water is not available and total hardness is over 200 ppm . In fact , almost no one prefer to apply Ion exchanger for Tehran city water ,especially north part of Tehran which is called up market places . I have not tested the city water for total or Calcium Carbonate , and you pointed out good point . i will do it and share it very soon .

    Thank you for your constant support and solutions which you share them with us . We treasure your help .

    Now, We have been working on renewing the hot and secondary return manifolds of the boiler room ,and we will attach the photographs of the inside of those corroded manifolds as soon as we dismantle them . There is obvious pity corrosion from inside of the branches of those manifolds which white deposits have stopped leaking out .



    Sincerely,

    Roohollah
  • MikeSpeed6030
    MikeSpeed6030 Member Posts: 69
    edited August 2016
    Wow! I can only say what is prevalent here in the U.S. Midwest. We normally use standalone natural-gas-fired water heaters not connected to the heating boiler (but your boilers surely aren't for space heating in Tehran?). A standard glass-lined, 40-gallon gas water heater here lasts for 15 years, or more (my last one lasted for 50+ years), depending upon the water quality. Usually they fail by springing a leak - then they are replaced for maybe US$300, plus labor (but many of us are do-it-yourselfers - the only big chore is getting the old heater out of the basement).

    The main thing I can suggest is to drain the tank a bit every month to eliminate solids.
    Roohollah
  • hot_rod
    hot_rod Member Posts: 14,753
    It also looks like high iron content or the tank has areas where the galvanizing is failing

    A complete water analysis would determine exactly what is in the water, how much, and what treatment

    Many options to "fix" water but it gets $$ to install and maintain large quantities. Most owners prefer to treat symptoms not causes
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Roohollah
  • Roohollah
    Roohollah Member Posts: 118
    Thank you for the posts .There are practical points to derive ,as always .

    As our friend asked , the boiler just provides heat for domestic hot water tank ( 1200 lit - indirect type ) and towel warmers in floors ' baths and swimming pool and spa heat exchanger and their deck .

    That is true . There is reddish and mud like substance at the bottom and the wall of the tank ,especially where galvanized coating fails . We some times brush and clean the corroded parts of this type of tank in order to apply Epoxy to prevent corrosion or prolong the longevity of the tank .But, as you stated , home owners most of the time prefer to economic solutions or some how transient antidote to get the job done . Also, lack of reliable products or old school type of products makes this story to dominate plumbing world in our area for years .

    believe it or not , when we order this type of tank to our trusty tank maker , he always says that the points that we put emphasis on them to be complied by the tank maker never other guys ask him to do it . For instance, Thickness of the tank 5 or 6 mm , hot galvanized sheet , the thickest threaded sleeves for inlet ,out let , saftey valve and drain valve. tube bundle 7/8 with 0/9 tube bundles , putting metalic barrier inside of the tank while they are welding or cutting during the time of construction in order not to damage the galvanized coating .As you know, respecting these point by the tank maker will result in increasing cost of the tank nearly 30 to 40 % in comparison with ordinary tanks .Here, we just endeavor to install more reliable products for providing home owners with much more peace of mind .

    I am sorry for such a long story . Thank you for your support and patience ,


    Best Wishes,

    Roohollah,

  • hot_rod
    hot_rod Member Posts: 14,753
    Same with over here, tanks are a commodity product, and manufacturers are typically looking for way to take cost out, not add it in!

    Certainly you can have custom tanks built with thicker steel, better coatings, etc.

    We typically glass or cement coat steel tanks for domestic hot water, or epoxy coat for special applications.

    Stainless steel tanks are another common option, many of those are now sourced from China, or at least the heads, then welded to the tank over here.

    Galvanized steel was common for well tanks, I don't see many fired or indirect tanks of galvanized construction. Well pressure tanks are typically thin steel construction with a bladder inside, now.

    There are some crazy laws about when a product can state made in the USA, a % has to be assembled or manufactured here, or it has to state the country of origin if it is imported complete.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Roohollah
  • Roohollah
    Roohollah Member Posts: 118
    With regard to Total harness of the city water , I tested the water and realized that The total hardness of the city water to the above project is 119 ppm at this time . I would like to know that whether it is recommended to soften such a water in terms of healthy views or even in terms plumbing codes ?

    Thanks for all the views and comments ,



    All the best ,


    Roohollah,
    Charlie from wmass
  • SWEI
    SWEI Member Posts: 7,356
    Assuming that's total hardness, it comes to about 7 grains. That's on the low side of hard by most standards, but if the ΔT is high enough (which it is on a relatively small coil) you will get a lot of mineral build-up.
    Roohollah
  • hot_rod
    hot_rod Member Posts: 14,753
    Most potable codes or water quality requirements deal with bacteria or harmful minerals, heavy metals. I don't know of any recommendation for water softness, it is a personal or business decision. A water softener basically exchanges bad ions (hardness" for less bad ones :) It does not strip all the minerals out.

    Only a complete water analysis will tell you what minerals and what levels you have. Just from the pic it looks like high iron, and a softer will not handle that well. I use a product called an Iron Curtin to treat my high iron content well water.

    I also have a softener on the hot water, and carbon filters under the sing for drinking water. Each one serves a different purpose.

    How long has that coil been in use, it's not really that bad. perhaps every 2 or 3 years it needs to be removed?

    They can be cleaned by running a mild acid cleaner through the tank.

    Determine the capacity of the tank, then see how much acid cleaner would be required. Maybe it comes out less expensive to acid clean it without removing?

    I've used a product called Hercules Sizzle for that purpose, I will link the info sheet.

    Remember also, you have a fairly low hardness, but that is a measurement of calcium and magnesium. It is possible to have a low number on softness but a high TDS, as TDS total dissolved solids is all the minerals hard and soft :) in the water.

    For those conditions generally a RO unit is used. Car washes for example use that technology to get spot free rinse.

    RO is an expensive process there is a lot of water, and the membranes need service, it to could be cost prohibitive.

    Generally speaking the customer that complains of the cost of you doing that cleaning will not invest in water treatment.




    http://www.caleffi.com/sites/default/files/coll_attach_file/idronics_18_na.pdf
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Roohollah
  • Roohollah
    Roohollah Member Posts: 118
    A profuse thanks for the new posts and cordial support too . The link is great source of learning for me and guides me to have better view over scale build up over tubes and pipes .

    As regards TDS , I would like to mention that the water make up to the DHWT is 141 ppm that I measured today morning ,and we are about to changing those corroded manifolds during this week and I will share the result .

    Here, we just have access to HCL acid and other domestic products to remove temporary scales . The tank capacity is 1200 liters and it must be dismantled to be acid washed due to its gaskets which are so prone to mild acid . Also, the tank does not have hand hole to remove dirt and deposits ;so, the practical way is to dismantle the tank and renew the gaskets and remove whole dirt . Indeed, the way you introduced is professional method to acid wash with out dismantling the tank . To be honest , if this method were possible in here, most customers never pay to the job . In fact , to their eyes , the job is so easy and most of them say they could do that why do they need to hire heating installer to do it .

    Once more, Thank you in advance for supporting us brootherly and sharing your invaluable experiences and knowledge with us .


    Best Wishes,

    Roohollah

  • hot_rod
    hot_rod Member Posts: 14,753
    Although they are disappearing we have radiator shops around here. They have a large acid bath tank that they dip radiators for trucks and industrial equipment to de-scale them for cleaning and leak repairs.

    I have a customer that takes his DHW flat plate HXers to them to flush out every few years.

    Your water quality numbers do not look bad, even for the boiler side.

    Here are water specs from a few different boiler manufacturers.

    I think what you have there is what we call "job security". that coil will need regular removal and cleaning :)

    If you use acid be very careful you can weaken or pin hole thin walled copper


    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Roohollah
  • Larry Weingarten
    Larry Weingarten Member Posts: 2,129
    Hello: You might want to see if magnesium anodes can be installed in the tank to prevent rusting and keep it going. I didn't see evidence of the tank having anodes. Powered anodes might be a good choice also. ;)

    Yours, Larry
    SWEIRoohollah
  • Roohollah
    Roohollah Member Posts: 118
    Dear Members ,

    I profusely thank you all for providing me with more reliable info and practical solutions to do the job better that before . Indeed , I do appreciate such a hospitality and warm greetings which always live up my time in this corner of the world .

    As Hot Rod stated above, the quality of the water is not that bad ,and this type of indirect tank roughly needs to be acid washed every 6 to 8 years in north part of Tehran , but in fact , the more water gets hotter inside of the tank , the sooner the tube bundle gets covered of Carbonate scale . Most of the owners just prefer to get their tank acid washed when Gas bill goes up sharply . Also, there is an other type of indirect domestic hot water in here which is made by galvanized sheet . i do not know what it calls it in English , but in here it is named two layers galvanized tank in which the inside tank flows domestic hot water to baths and kitchens and outer layer flows boiler's hot water . This type of the tank is about nearly to abolish in here ,but still some old timers prefer them to install in some complex buildings . This type of tank does not need any acid washing and it gives service for nearly 10 to 15 years and when the inside layer gets corroded and water pressure of domestic system penetrates to outer layer , the tank must be changed .I have attached a photograph of this type tank when we installed forcefully for the last time . ( The owner bought it earlier and we had to install it ).


    AS regards magnesium Anode rod , the manufactures of both introduced types of domestic hot water tank never equip them with it , I some times try to do it but i could not find it on the market . This protective rod is available in direct gas or oil domestic hot water which is pretty custom amongest those one family houses in down town and some center districts of Tehran .


    I am sorry for the long story and thanks for your patience,


    Once more, I sincerely do appreciate for all your support and beneficial posts that I do treasure them .



    Sincerely,

    Roohollah

  • hot_rod
    hot_rod Member Posts: 14,753
    The water treatment folks tell me for every 20° increase in temperature corrosion and scaling potential doubles.

    Elevated temperatures in fired water heaters and indirect tanks does reduct the life expectancy. I suppose both the thermal stress of going from 40F to 160F and the additional mineral precipitation have a part.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Roohollah
  • Roohollah
    Roohollah Member Posts: 118
    Dear Members ,
    We are dismantling galvanized hot water and secondary hot water return headers in the boiler room . As we started doing this , we realized protecting metalic pipes against scales in high temperature zones is much more complicated and needed precision maintenance .The time we installed the boiler room nearly 11 years ago , we did not have today's view upon water chemistry . We thank God for such an opportunity to have friends like you all who guide us to deal with this industry mysterious phenomenons .

    As we have traced down for a solution for making more reliable and cleanable headers for domestic hot water , we have come up with this idea that the only affordable choice is to have the header which will be cleanable ( acid washing ) , no branches of galvanized pipes which are thin and very prone to pin hole due to build up scales , and thicker galvanized pipe as main pipe for making it into a header ( sch 40 ) , thickest full galvanized threaded sleeves( 4mm ) which will be suitable for welding ,and brass nipples which covered by Nickle ,full port ball valves ,and Uponor aqua Pex (10 bar ) for supplying water to the floors .We have done this method for 5 years and it looks more reliable and affordable for our customers and if any problem happens ,such as pressure loss over time ,it will be a remedy like bright dipping . We wish that Viega propress or Uponor in line manifolds ( 2" ) would be available in our area to forget this nerve racking situation .

    We have attached some photographs of the introduced headers and corroded domestic hot water pipes of this boiler room .


    We would like to hear your thoughts and take on this type of the header .

    Thank you in advance for your time and posts ,


    Sincerely ,

    Roohollah
  • Roohollah
    Roohollah Member Posts: 118
    I am sorry I could not attach the photographs , I have tried it to do it .
  • Roohollah
    Roohollah Member Posts: 118
    Thanks you all for considering the topic in details and provide us with more reliable solutions . I do appreciate the managers of this Site to give me this opportunity to learn more and more.


    I have attached the photographs that I promised above . I wish I could hear from you .








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