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schoonmakerjon

Fresh water tank replacement

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All, I'm evaluating replacing the RV fresh water tank.  It is the original and ~20yrs old.   The tank's drain fitting has a minor leak, (see pic, lower right) that I've repaired once, sealing with SikaFlex 221, having some success, and not completed fixing.   The tank is ~45"long x 22"tall x 21"deep, and I expect this is ~80gals+.  the standard tanks are available online and YouTube videos illustrate how to insert and seal the fitting outlets.  This tank needs 4 outlets, a drain, water pump connection, fill port and air vent.  I am interested in anyone having taken this DIY approach and understanding the work effort and the reliability of these outlet seals.

Another approach is to go to a plastic "welder" providing the dimensions and port/outlet locations.   I understand these plastic "welder" will then custom build the new tank.  This new tank would basically "pop-in" and I would only need to make the necessary connections, water pump, etc.   Alternatively, I could take the coach to the plastic "welders" and they would build and install.   Again, I'm interested in folks that have taken this custom build approach and your overall cost and success.  Please advise any recommendations/suggestions and overall experience.    Thank you.

water_tank.jpg

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If the tank is in good condition other than the leak, you can have the tank repaired and a new drain fitting installed.

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1 hour ago, richard5933 said:

If the tank is in good condition other than the leak, you can have the tank repaired and a new drain fitting installed.

I think that is the way I would go.

Bill

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Bill and Richard,   this is quite helpful.   what groups do these repairs?   Plastic welders?  Tank specialist?   Easily found via an Internet search?   Please let me know any supplier pointers.

Also, I've found some Uniseal products that could fit/seal this opening and these products indicate a reliable seal.   Do you all have any pointers about these Uniseal products?  There are numerous YouTube videos illustrating application/use.    thank you.

 

     ---  Jon

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A Plastic Welder would be where I would be looking. It does take a special torch to do the process. The last time I saw it it was a hot air gun using heated nitrogen with a feeder tube for the plastic rod as a filler material. Kind'a like a Hot Glue Gun.

Seeing your tank, it may have to be removed to do the weld due to space restrictions. However that may have changed since I last saw the process working,

Herman

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You're likely looking for a company that does spin welding. That's what the technique is called that is used to install the new fitting. Who ever does that should also be able to handle other repairs to the tank.

If you can't find a shop by using that term near you, try looking for the nearest plastics supply house. They should be able to direct you to a shop in your area that can do the work.

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8 hours ago, schoonmakerjon said:

Also, I've found some Uniseal products that could fit/seal this opening and these products indicate a reliable seal. 

Not familiar with that product but I bet there are some epoxy products that will work on that type of plastic. I don't know how much it would cost to have a shop do a hot air weld repair but they have guns on Amazon for around $100.00 + https://www.amazon.com/s?k=hot+air+plastic+welder&hvadid=77653062753171&hvbmt=be&hvdev=c&hvqmt=e&tag=mh0b-20&ref=pd_sl_7y3qv1xc3o_e

I would look at you tub and look for videos on how to do it. Then decide if it is something you want to try.

Bill

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Uniseal products are rubber seals which use a tight friction fit. Insert the seal into a hole in the tank, and then a PVC pipe is inserted into the rubber seal. The seal is made by a tight friction fit. Although some have used these as permanent solutions, I'd only use them as a temporary solution, as the rubber is going to harden and shrink over time.

Trying to glue a plastic tank is difficult, especially near the drain or other parts of the tank which are always wet. On the top it is easier to use glue or epoxy since there is no water pushing on the repair, but even then it's difficult to get things to stick permanently to the type of plastic used in most water tanks which is why they use spin welding.

The best solution is to get a new fitting put on with spin welding. Next would be to use a plastic welding gun and some appropriate plastic welding rod to make a repair. I've done this, and while there is a learning curve it's not that difficult for anyone who is used to doing similar things.

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Any competent auto-body shop should be able to plastic-weld the pipe into the tank, IF you can clean all other sealants off the parts. You must know the type plastic of the tank.

Edited by rayin

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Richard, I remember when you went thru the learning curve on your tank!  Perhaps you can PM the OP and help out?

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30 minutes ago, manholt said:

Richard, I remember when you went thru the learning curve on your tank!  Perhaps you can PM the OP and help out?

Good point. My leak was along a seam line and quite easy to fix. A crack next to a fitting is slightly different, but depending on the severity of it there is still a chance an easy fix would work.

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All,   I appreciate everyone's replies and insights.   Also, a respondent has encouraged me to continue to describe the repair activities and process here.   

After making one SikaFlex 221 sealant repair attempt with limited success and your all feedback, I located a somewhat convenient plastics fabricator, Emco Plastics, in NJ.  I was able to remove the tank and transport it to Emco, yesterday.   This firm appears from my research and yesterday's conversation to be a well informed and a knowledgeable crew.   They will do both the plastic and spin welding for 2 new fittings, drain and pump.   The drain fitting is visible in the prior picture and behind it, same side, is the pump connection fitting.  At this point the estimated price range is $250-$350, and this might change based on the fittings needed.   I'm expecting to have this work completed in 2-3 weeks.

As some background, this tank was the original installation in a MCI bus conversion done in ~2000.   I purchased the coach from the original owner, then operated as a celebrity coach for industry participants ~ 1 year ago.  There is indication this drain had been leaking for some time, years?, given the plywood layer/section under the drain is deteriorated and will need to be replaced/patched.  The Emco plastics fabricator, doing the initial tank inspection yesterday, did confirm that any attempt to fix and/or seal the leak with any approach other than plastics/spin welding would only be temporary and fail.  So again I appreciate everyone's experience and feedback here, and finding what appears to be a competent plastics fabricator for these repairs.

I'll provide follow-on updates and a brief reinstallation description as these activities occur.   Also, since I've limited pumping experience, I may have some added questions for folks following this thread, particularly about rebuilding and making the pump connection.   I intend to do this with PVC piping.   Thank you for everyone's help and insights.

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Thanks for the update. Would be great to see photos of the repaired fittings when you get the tank back - maybe even before you re-install so we can see how they put them in. You're certainly not the only one that will face repairs like this, and I think the added information you're providing is helpful.

Edited by richard5933

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All following this topic,

I signed the contract today, for EMCO to do the work, so I'm expecting 2-3 weeks for completion.   Their work includes 2 new fittings, drain and water pump connections, to be installed in the tank.   The est. cost is $300 for both the plastic welding repairs and fabricating/installing the 2 fittings.  I'll have pictures once the repairs are complete and will post here.

Additionally, I'm expecting to use PEX piping to make connection from the tank to the pump, as PEX is now available in 1" piping.  If you all have some experience/insights here, please do pass them along.

Also, I'm looking for any insights/recommendations for securing the tank in the water bay/compartment.   Thank you.

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1 hour ago, schoonmakerjon said:

Also, I'm looking for any insights/recommendations for securing the tank in the water bay/compartment. 

How was the old one held in? The picture shows groves like it was held in with straps.

Bill

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I agree that something could easily be rigged up using the two grooves across the top of the tank. If you have a small (1" or so) curb on each side of the tank to keep it from sliding, then the straps only need to be snug enough to keep it from bouncing upwards.

Are you thinking of using 1" Pex tubing for the outlet of the freshwater tank? Not sure that it's necessary to go that large. The plumbing for my whole house is only fed with 3/4" copper pipes from the well, so using 1" for the water outlet on the tank would certainly be overkill. My 90+ gallon freshwater tank is connected to the bus with 1/2" copper pipes, and we've never had a problem running multiple plumbing fixtures at the same time.

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As Herman pointed out, the small block in front was probably meant to prevent the tank from sliding, most likely one on each of the three other sides. If this was mine, I would add two straps across the tank where the cross ribs are. Being an MCI conversion, the floor is heavy aluminum, you can use metal straps fitted into those ribs and use stainless steel bolts to attach this to the floor of the compartment. Be sure to place some material such as rubber between the strap and the 90 degree bends on the tank. Also I would use either a rubber mat or carpet foam under the tank instead of plywood. I have almost the same setup in my coach, except I used two forty gallon tanks side by side to limit height, my waste water tanks are mounted above the two fresh water tanks. One other thought, you can drill through that floor to secure the straps, just make sure that no pipes or wiring will be drilled through.

 

water_tank.jpg

Edited by kaypsmith

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14 hours ago, manholt said:

Kay, black over fresh?

Yes, nearly every MH that I have worked on, quite a few, are set up that way. Black, gray, and fresh are sealed units, the overflow on the fresh is pointed downward, so no chance of mixture there. The black and gray are in most cases dependent on gravity emptying them, even with a macerator the entrance to the macerator depends on gravity, while the fresh uses a real pump to send the fresh water to the faucets within the coach.

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I agree with Kay. However I can just see the germophobic crown reaching for their bottle of sanitizer just because they read that. :lol::P

Bill

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Hello all following this thread,

The tank is repaired and a picture is below.   This work was done by Emco Plastics, Cedar Grove, NJ.  When looking at the prior tank picture, the drain value and the pump connection lines (although not the tank connection fitting) are both visible on the right side.   I pulled the tank myself bringing it to Emco and it took them ~3 weeks to complete work, including fabricating the pump and drain connection fittings.   Again see pic.   The drain fitting is 1" diameter (left) and the pump fitting is 1 1/2" (right).   The prior pump fitting was 1", and I'm planning on stepping the new fitting to 1", as I believe this will be a more effective match to the pump.  Also, I'm planning on using PEX for these new connections.

As I understand Emco's tasks here, the following was done,   1.) old metal fitting were removed, 2.) matching plastic patches were "welded" in place 3.) new matching plastic, threaded fitting were fabricated 4.) these new fittings were spin "welded" in place and.   5.) fittings were sealed and all work tested for leaks.   Total cost ~$360.00

Here is the repaired tank picture with explanation.  The 2 new  outlets are at the picture bottom, drain is left and pump right sides.  In this picture the tank is on its end and the orientation from the fully installed tank is to turn the tank 90degrees counterclockwise, i.e. you are now looking at the tank's right end.  The prior metal fittings are sitting in the ~lower/middle of the picture.   Drain lower left and pump center, extending to top.   In the upper part of the picture the fill spout is visible, upper left and the overflow spout, lower right.

Your comments about securing the tank in place are all helpful/useful, and I'm currently planning on using marine plywood, as suggested by the prior owner.  Kay's comments about a rubber mat makes me rethink the plywood.  However, plywood allows using plastic blocks, replacing the wood, and securing these to the marine plywood panel to prevent the tank moving.   The prior owner indicated previously the tank has a tendency to "walk" toward the storage bay door, and the wooden blocks, secured to the prior plywood panel prevented this movement.  Unfortunately, the leaking rotted this floor panel, and marine plywood will hold up to occasional water spills.

I'm planning on doing the tank re-install Friday, 5 March with some plumbing help, as I do not have PEX experience nor the needed crimp tool.   This RV repair person has both.   Please let me know any questions and/or re-install directions.    Thank you for your help and interest.

 

repaired_tank.jpg

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