Reliability SuperStor tank

U023

I'm a consumer in the SF bay area. We use a Munchkin with SuperStore SSU80 for DHW and radiant heat. The tank is about 5 yrs old and has developed a leak near bottom of tank. See pictures for rust near welding seams. Is this a common problem? Should I expect this to be covered under the lifetime warranty? The warranty does not cover return shipping (cross country) or installation. Are there any better products? I would prefer not having have to go through this every few years.

Jean-David Beyer

I have no idea....

... what went wrong with your Superstor, but when you find out, please post what went wrong with it. The inner tank is 316L stainless steel that should resist domestic hot water heater for well over 5 years. The "outer tank" should have no water in it and is just to protect the 2 inches of foam insulation.



Unless your domestic water is seriously corrosive, about all that could have happened is the welds of the inner tank (one at top, one at bototm, possibly one along the side. Or the pipes coming in or out breaking loose from mishandling. But I am not a techie and do not have an answer for you. I hope you have one for me, just for my own curiousity.

Andyk

SS Question

Do you have a Thermal Expansion tank on the unit ? If not and if your water meter has a check valve in it~the thermal expansion has no where to go. This can build stress on the tank and make it fail prematurely. 

Brad White

I tend to agree

with Andy and JDB-

I would start with a water sample for chlorides and system pressure. On the pressure side of things, you do have (or darn well better have!) a T&P valve and a vacuum breaker.  If a back-flow check valve, yes, a thermal expansion tank is highly recommended if not required by your plumbing code.



Absent any these, you have a bomb that does not tick and/or a beer can in the hands of a weekend bar warrior.



The rusty water stains say chlorides to me and even 316L stainless is not immune. Put another way, when stainless corrodes, it rarely puts out rust like that, if that is what it is. Coupled with a pressure incident,



The boiler-water exchanger is cupro-nickel and should last as long as the tank absent chemical or heavy mineral interference. The natural expansion breaks out most encrustations.



I have had HTP SuperStors  in service for years, both my own homes over the years and specified. The only ones I saw fail were in a pool equipment room when I got there.

Jean-David Beyer

Looks as though he has a P&T valve near the top.

That copper tube goes slightly descending from it down towards the left wall. It may be too long, but it is there.

Brad White

I could not tell

for sure. I also cannot see the vacuum breaker and there are isolation valves near the connections, between the tank and the breaker. Won't pass inspection here.



An inadvertent closing and draining and you will hear the sound track for "Das Boot".

bill_105

Why would...

the lack of a vacuum breaker cause a leak in the tank?

About 5 years ago I had a leaking super-stor. It was a factory installed immersion well causing it. I caught it early on. Those wells have like no taper in it's threads  All is well now - that ends well, I guess. As for the rust, that plastic pan-like thing that holds the jacket and everything together retains water, and the jacket is steel.

This retaining water deal is no joke. Seems like a symptom of a certain person I live with. Good luck!

Brad White

Vacuum Breaker

If you do not have a vacuum breaker on a tank and you drain the tank against a closed inlet valve, atmospheric pressure can crush a tank. Not all of them but many.  A drain down incident may be enough to stress a weak weld. "Stresses follow strength until they find the weakness."



The strength of a tank (pressure vessel specifically) is in tensile strength resisting internal high pressure. All of that metal is pulling, usually evenly, and tensile strengths are rather high.



But reverse that and draw a vacuum (essentially allowing atmospheric pressure to push in toward the vacuum now inside the tank), and the tank may be crushed like an eggshell or at least dented a bit under 14.7 psi of pressure.



You can also see this in ductwork. It is easier for round duct to withstand higher pressure but much easier to crush it from the outside. Ductwork rated for high negative pressures (such as wood shop dust collection),  tends to be of thicker gauges and/or more reinforcement than positive pressure ductwork.



Try an experiment- Take a 2 liter plastic soda bottle and fill it with water held tightly to a faucet. Short of taking a shower, that 50 or so PSI can be held there for a moment. Plastic in tension.



Now take the same bottle filled with water, right to the brim. Put a filled hose on the bottle with a hose clamp, tightly. Drop the hose out a second story window to grade and invert the bottle to let the water out from the bottom of the hose. Once the water starts to draw, the suction (vacuum) will be less than atmospheric pressure and the bottle will crush.  A vacuum breaker (a Bic pen for that matter), would relieve this at the bottle.



You can also do this with metal cans such as for brake fluid (metal cans that can be re-sealed), by closing them after heating and letting the cooling collapse the can. I do not recommend this because torches, metal cans, human flesh, not a good combination.



But try the hose trick. You will see what I mean and your neighbors suspicions will be confirmed.

Alan (California Radiant) Forbes

SuperStor

This gentleman is my customer.  He called me in because the original installer does not do service work.



HTP, the manufacturer required him to have a licensed professional look at the leak and make a report.  As you can imagine, it's impossible to see exactly where the leak is coming from without removing the jacket and that amount of rust could not possibly come from the tank itself.  I'm making an educated guess that the leak is coming from a weld.



Water quality here in the East Bay is excellent with only minimal amounts of dissolved solids and minerals and no corrosion issues.  Other answers:



- There is an approved relief valve on the water heater.  The drain is the horizontal pipe you see running from the tank to the wall in his picture.



- I did not look for or notice a PRV or a domestic expansion tank. 



- I did not see any corrosive solvents or chemicals in the mechanical room.



- No vacuum relief valve.  This is not a common device installed in this area, but I agree, maybe one is necessary with this kind of track record - cheap insurance.



I'm surprised no one mentioned an electrical problem, i.e. bad grounding.  It seemed adequate (gas to hot to cold).  Is there an easy way to meter this?



Leaking immersion well?  Hmmmmmmm.  Maybe I should make another trip?

Brad White

Electrical problem

Good point on that one, checking the cathodic protection. Any dielectric nipples (those ball check type devices? May negate it and break the continuity. But good point and a test to run or at least another trip!

tim smith

Re: Superstor tanks

I just had my 1st failure. I tore off the cover after approval for field scrap, scraped off insulation and found the weld had failed around the upper 1.5" outlet nipple. This was an ssu 80. 1st failure out of almost 50 installed over the last 6 yrs.

MANPE

SUPER-STOR FAILURES

While the Super-Stor tanks are made of 316-L Stainless Steel, apparently the welds were not made with the proper welding wire or welding procedure.  316 and 316-L MUST be welded with 316-L welding wire.  The last time I checked the going rate for 316-L welding wire was $12,500. per 50 pound roll.  I wonder if they used a cheaper wire to weld?  Another problem may be with any deep weld, the metal MUST be annealed after welding.  The heat from welding causes the molecules that prevent corrosion to migrate away from the weld.  Annealing is the only way to correct the alignment of the molecules back to 316-L formula.

I would recommend a glass lined holding tank for any municipal water application.

MANPE

icesailor

Tank Vacuum:

Brad,

That's an interesting analogy but although 100% correct in the situation you described, it isn't in the real life application of the draining of the tank.

When you drain the tank with a vacuum valve plugged, or no vacuum valve, the vacuum head pressure isn't any higher than the top of the tank. It only takes enough vacuum pressure to hold the water at 5". The same as taking a well pump and lifting water from 5' below the pump end. It will never be any higher. Unless you do what you describe. Take a 50' hose and hang it out a window in a 10 story building. Then, you can get 30" of vacuum on the tank and collapse it. If you put a water pump on the tank and "suck" the water out of it and the vacuum valve fails, you can collapse the tank.

That's why I now only drain water heater tanks or anything, with an air compressor. When I drain houses, I first connect my air compressor to the water tank and start it up. Then, I go upstairs to start bleeding out. After I drain one toilet, the water heater is drained. When I use a pump, if the WH drain valve had a bad packing, the vacuum leaking would cause the time to drain the tank to sometimes be 1/2 hour. With air, it takes less than 6 minutes with a 80 gallon water heater.

The hose on a water bottle is an interesting analogy. What you are describing though is best understood as like sucking water from the ground. The higher the lift, the farther from the ground the water is, the higher the vacuum needed to lift it up to ground level. The longer the hose from the bottle, the greater the vacuum will be because the air wants to go up the 50 ' hose. And if it was a clear plastic hose, I think you would find that the water wouldn't run out the end of the hose but would be at a level, no more than 33' down from the bottle.