How much can a stainless steel tank rust inside?

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  • #1
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There is a lot of rusts in my water supply. Im suspecting the inside of my stainless steel pressure water tank is rusting.

But can the stainless steel pressure tank rust inside?

When i put magnet it doesnt stick to it.

I plan to replace it with very expensive Aquaflow pressure tank because I assume its so rusted inside. Been thinking for months.

Wish i didnt sell my fiber optic scope so i could peek inside.
 

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  • #2
jrmichler
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You could disconnect the piping from the tank, shine a light into one opening, and look in the other opening. The pipes look like galvanized steel. I would look at the piping for the source of rust before looking at the stainless steel tank.
 
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  • #3
Baluncore
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Stainless steel is only stainless in the presence of oxygen. If the water contains sulphur or chlorine then the steel may be corroded, but the product is usually a black crumb.

Water flowing over stainless steel will deposit iron from the water in the surface that will give it a rust colour as the added iron oxidises.

Your tank is almost certainly OK. It is the pipes you must check.
 
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  • #4
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Thank you.

20200903_133144.jpg


Another reason i plan to change to bladder or diaphragm pressure tank is because i think there is a hole in my existing stainless steel pressure tank.

Actually the pump has not been running for years (there is defect sometimes it wont turn on). This is because when i turn it on. Pressure in tank can reach 40psi but then it goes down to 18 psi in 2 minutes. I dont use check valve or one way valve so not sure if it is leak on tank or lack of check valve. However my system running fine without check valve for 7 yrs prior. Now i dont know if the pressure at souce gets lower so water in tank goes back just now. Possible?

Anyway in case i wont use the pump. And replace the tank with newer bladder or diaphragm tank. If my water souce is 18psi. Will i still get 18psi after the tank or would the bladder or diaphragm turn it to just 5psi or something if i dont use pump (because 18psi is sufficient for my home use)? Something about materials deflecting energy or absorbing them in deformation.

By the way. If there is hole in tank. Can it maintain 18psi constantly (with pump off)? If you will put 18psi pressure in a tank and put hole. Could it get out? What you think?

20200903_141855.jpg
 
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  • #5
Tom.G
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That pressure leak down to 18psi sounds like a pump seal or check valve is bad, or maybe there is a leak in the building plumbing that you haven't found yet. Leaks in toilets are rather common, either the float valve or the flush valve. If it is a centrifugal pump there is a check valve Somewhere. A positive displacement pump will have a valve or two of some sort; although if it is designed for a positive source pressure they may not be obvious (think of a 2-cycle engine). The pump may just be worn out.

In your photo, there is a rust deposit around the pressure gauge, could be a leak there or within the gauge.

The plumbing at the bottom of the tank looks like there is an adapter or reducer there that shows as black in the photo, is that corroded or the wrong material?

Much cheaper to investigate those than replace the tank!

And I fully agree with @jrmichler and @Baluncore on the pipes being responsible for the rust deposit. In fact that was my first thought when you mentioned it. Could also be the pump rusting, or the water source is high in Iron.

Tip: When you see a problem, try to think of ALL the possible causes, otherwise you are using what's called the 'shotgun' approach; throwing a bunch of 'fixes' at it and hoping something hits the target. :wink:

Let us know what you find.

Cheers,
Tom
 
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  • #6
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That pressure leak down to 18psi sounds like a pump seal or check valve is bad, or maybe there is a leak in the building plumbing that you haven't found yet. Leaks in toilets are rather common, either the float valve or the flush valve. If it is a centrifugal pump there is a check valve Somewhere. A positive displacement pump will have a valve or two of some sort; although if it is designed for a positive source pressure they may not be obvious (think of a 2-cycle engine). The pump may just be worn out.
If the tank has hole. Musnt it go to 0 psi?

Or the hole rate of atmospheric dissipation is matching the pressure of the source? Im thinking what newtonian principle can maintain the 18psi.

There are gate valves at inlet and outlet of tank. Ill try to turn them off at same time after pressure reach 40 psi.

I cant just turn them off bec when i do and my GI metal pipes have no water. Ill have rusts in my faucets after turning them on.

Isnt there any special liquid or material that you can let flow to the pipes and it coating the rusts all over the pipes with plastic film? This will be useful to millions of old houses.

In your photo, there is a rust deposit around the pressure gauge, could be a leak there or within the gauge.

The plumbing at the bottom of the tank looks like there is an adapter or reducer there that shows as black in the photo, is that corroded or the wrong material?

Much cheaper to investigate those than replace the tank!

And I fully agree with @jrmichler and @Baluncore on the pipes being responsible for the rust deposit. In fact that was my first thought when you mentioned it. Could also be the pump rusting, or the water source is high in Iron.

Tip: When you see a problem, try to think of ALL the possible causes, otherwise you are using what's called the 'shotgun' approach; throwing a bunch of 'fixes' at it and hoping something hits the target. :wink:

Let us know what you find.

Cheers,
Tom
Ill check more. Thanks!
 
  • #7
jrmichler
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Keep in mind that pressure gauges fail. You don't know that zero on the gauge is really zero unless you physically remove the gauge and confirm that zero is zero. It could be pointing to 18 PSI at zero pressure, or it could point to 18 PSI at, say, 30 PSI.
 
  • #8
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Keep in mind that pressure gauges fail. You don't know that zero on the gauge is really zero unless you physically remove the gauge and confirm that zero is zero. It could be pointing to 18 PSI at zero pressure, or it could point to 18 PSI at, say, 30 PSI.
There is bottom plug in the tank. When i open it.. the pressure further drops to zero psi. So it is under pressure. Last year i tried closing the inlet and outlet gate valves right after tank. Pressure continued to drop from 40 psi to 18psi. Tomorrow ill do it again to make sure pressure drops before i have the tank removed on saturday. Plumber charging expensive so thinking twice.

Last week after opening the bottom plug after 2 years of not opening it. Water couldnt flow out because so much rusts and sediment collected at bottom of tank and i had to insert wire to remove sediments. But after plug remained opened for 30 mins. All water came out with 18psi go down to 0 as water splashed out. So imagine how dirty inside tank.
 
  • #9
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Ok. I turned on the power pump and closed the output gate valve of the pressure tank. Pressure still went down from 40 psi to 18 psi. When I tried to close the input gate valve of the pressure tank (located before the pump) with the tank output still closed. There was no decrease from 40 psi to 18 psi anymore. In other words, no leak anymore so water is returning to the souce.

So it's the lack of check valve causing pressure loss. Here is the weird thing. The house had no check valve for 8 years and pressure didn't go down but can be mainted at 40 psi. Say. If the water company has poorer pressure now, the water in the tank can go back to the source? But before even when it was 40 psi, the water didn't return even without check valve. So usually what must be pressure difference before water gets back to the source?

Thank you.
 
  • #10
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Ok. I turned on the power pump and closed the output gate valve of the pressure tank. Pressure still went down from 40 psi to 18 psi. When I tried to close the input gate valve of the pressure tank (located before the pump) with the tank output still closed. There was no decrease from 40 psi to 18 psi anymore. In other words, no leak anymore so water is returning to the souce.

So it's the lack of check valve causing pressure loss. Here is the weird thing. The house had no check valve for 8 years and pressure didn't go down but can be mainted at 40 psi. Say. If the water company has poorer pressure now, the water in the tank can go back to the source? But before even when it was 40 psi, the water didn't return even without check valve. So usually what must be pressure difference before water gets back to the source?

Thank you.
Here to visualize the above mystery.

20200904_102101.jpg
 
  • #11
Baluncore
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There may be a NRV outside the building, buried with a stop valve on the water main connection.
 
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  • #12
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There may be a NRV outside the building, buried with a stop valve on the water main connection.
All houses have NRVs (non return valve)? What would happen for those houses without?

I noticed last month the water meter moved clockwise then a bit anticlockwise for a sec. My water bill is twice higher. Do you knew a scenerio where non presence or defective non return valve can make the meter run higher?

Anyway last year i bought a 3/4" check valve at a store but didnt put it since i couldnt find a cheaper plumber. What would theoretically happen if you put a 3/4" check valve in the water pump that has 1" piping? And where is the best place to put the 3/4"? Thanks!

20200904_130714.jpg
 
  • #13
Baluncore
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All houses have NRVs (non return valve)? What would happen for those houses without?
You could push water back out through the water meter into the main. That might lead to contamination of the mains.

A 3/4 " valve has approximately half the area, so lower flow than a 1" valve.
Area 9/16 compared with 16/16.
 
  • #14
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You could push water back out through the water meter into the main. That might lead to contamination of the mains.

A 3/4 " valve has approximately half the area, so lower flow than a 1" valve.
Area 9/16 compared with 16/16.
I asked the water company. They didnt put any non returned valve underneath main water meter.

If the pressure tank is 40 psi and the water supply is 18 psi. The water can flow back? Even if say pressure tank is 20 psi. It can flow back?

But for 10 years prior to it. It didnt flow back. Maybe water flow from a supply is not measured in psi but something that perhaps matches 40 psi in the tank?

I read in the net check valve is not always required in pressure tank and pump.

This is a great unsolved mystery.
 
  • #15
Baluncore
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I read in the net check valve is not always required in pressure tank and pump.

This is a great unsolved mystery.
Plumbing standards differ. What country are you in?
A pump should have a NRV.

All houses have NRVs (non return valve)?
If there is debris in the water, such as you report accumulated in the tank, then any NRV may be jammed open.

You must draw a schematic diagram of the system. It will be impossible to guess what has failed without a full diagram.

All houses have NRVs (non return valve)?
Was that a question? Statements that end in a question mark are usually rhetorical questions that express doubt by the writer, but do not expect an immediate answer.
Questions in the English language usually start with the word "What, Where, When, Why, Who, Will, Is, Do", then the question ends with the question mark.
 
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  • #16
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Plumbing standards differ. What country are you in?
A pump should have a NRV.


If there is debris in the water, such as you report accumulated in the tank, then any NRV may be jammed open.

You must draw a schematic diagram of the system. It will be impossible to guess what has failed without a full diagram.


Was that a question? Statements that end in a question mark are usually rhetorical questions that express doubt by the writer, but do not expect an immediate answer.
Questions in the English language usually start with the word "What, Where, When, Why, Who, Will, Is, Do", then the question ends with the question mark.
Ok you convinced me a check valve is required and my pump and pressure tank have hidden defective check valve somewhere. Tomorrow expensive plumber coming and we will be in full gear ppe to fix all of it. They will put bypass and adjustable with gate valve so i can divert water to pump or direct to house at will. Thanks for all the tips guys. After this weekend over. Id forget all about plumbing.

To be on topic for this subforum. There should be liquid material that can coat all rusty piping surface with plastic. Perhaps some nano tech material that can sense metal and bind to it as it flow then turn themselves to colored liquid as extra is flushed out of water system after procedure done. This is because its not possible to take apart all piping and replace them manually because it would mean taking apart many concrete in the house and bathrooms.
 
  • #17
Tom.G
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The "hidden" check valve would most likely be either in the pump or at the tank inlet. Maybe it is that Black fitting at the bottom of the tank.

Putting any "plastic" coating in the plumbing has a few problems.
  • It would bond to the existing scale and rust in the pipes, however that rust is not strongly bonded to the pipe body. When the rust comes loose, so does the plastic.
  • You would have to remove every valve/faucet in the house, one at a time, to get the "plastic" thru each pipe without clogging the valves/faucets.
By the way, if they are not drained regularly, hot water tanks here in the USA can easily get 1/3 full of sediment over their lifetime, if even using city water. A clue they need draining is if you can hear them boiling when heating.

Please tell us what the plumber finds and what was done to fix the problem.

Cheers,
Tom
 
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  • #18
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The "hidden" check valve would most likely be either in the pump or at the tank inlet. Maybe it is that Black fitting at the bottom of the tank.
20200905_134431.jpg


The black fitting is just 1" to 3/4" adapter. So imagine the water pump hole and pressure tank hole is 1" but all the pipes are 3/4". Do you use 1" or 3/4" piping? Must it match?

Putting any "plastic" coating in the plumbing has a few problems.
  • It would bond to the existing scale and rust in the pipes, however that rust is not strongly bonded to the pipe body. When the rust comes loose, so does the plastic.
  • You would have to remove every valve/faucet in the house, one at a time, to get the "plastic" thru each pipe without clogging the valves/faucets.
By the way, if they are not drained regularly, hot water tanks here in the USA can easily get 1/3 full of sediment over their lifetime, if even using city water. A clue they need draining is if you can hear them boiling when heating.

Please tell us what the plumber finds and what was done to fix the problem.

Cheers,
Tom
The plumber will just add check valve and make gate switcheable bypass. He will just follow what i want. I wonder if i should use 1" piping between pump and pressure tank or just 3/4" when holes are 1"? But the rest of piping in the house is 3/4".
 
  • #19
Baluncore
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3/4” is sufficient for a single residence. Avoid 1” except where you need to join two 1” fittings. Minimise the cost of the fittings.

1” might be used on the low-pressure input to a pump, but in your case that is not needed since you have a significant positive input pressure at the pump.
 
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  • #20
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3/4” is sufficient for a single residence. Avoid 1” except where you need to join two 1” fittings. Minimise the cost of the fittings.

1” might be used on the low-pressure input to a pump, but in your case that is not needed since you have a significant positive input pressure at the pump.
Im not using pump the past 2 years. I just wonder what would happen if i eventually use the pump. The house piping uses GI that rusts. So i wonder if stronger pressure would accelerate or lodge the rusts in the piping more? What you think? My plumber cant compute it or not good in newtonian physics or hydrodynamics so cant answer.
 
  • #21
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Imagine you have a pipe with rusts in its inner wall. And you increase or decrease the pressure of the water. Do you think the pressure strength can affect the rate of how the rusts were being removed or flaked of and move along with water?
 
  • #22
Tom.G
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Increased water pressure in the pipes will allow a higher flow rate. This higher flow rate of course will depend on how far you open a faucet.

A higher flow rate will tend to remove some of the rust from the pipes. This may be an advantage or disadvantage.

Until the pipes get flushed of loose rust, you will get rusty water from the faucets, also any screen or filter on faucet aerators will need frequent cleaning, as will the shower head. After the loose rust clears, you should have even higher flow rates.

So it pretty much depends on what is important to you.

Cheers,
Tom
 
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  • #23
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Increased water pressure in the pipes will allow a higher flow rate. This higher flow rate of course will depend on how far you open a faucet.

A higher flow rate will tend to remove some of the rust from the pipes. This may be an advantage or disadvantage.

Until the pipes get flushed of loose rust, you will get rusty water from the faucets, also any screen or filter on faucet aerators will need frequent cleaning, as will the shower head. After the loose rust clears, you should have even higher flow rates.

So it pretty much depends on what is important to you.

Cheers,
Tom
I told the plumber to come instead on tuesday because ill buy sediment filters on monday..but your statement worried me. So rusty pipe can get out more from increased pressure, say from 18 psi to 40psi pressure, is this a definite or proven fact elsewhere, any experiments or paper about this?

Also wont the pipe continued to rust until all metal is converted to rust? Then i cant wait for the rust coatings to be gone, because the rust will just dig deeper.

If this is so. I wont use the pump anymore. Right now my shower heater has built in mini pump and adequate.
 
  • #24
Tom.G
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...any experiments or paper about this?
I'm not aware of any. Those comments (and those below) are from my personal experience/observation and that of a Maintenance Man I know that spends much time at an 80 year old building trying to prevent major floods.

Yes, increased flow (rust removal) can lead to holes in the pipe sooner rather than later; and of course higher pressure also leads to holes occuring sooner (higher pressure can push thru a thicker wall than low pressure. Just like a balloon!)

By the way, here in the USA nominal plumbing life (40psi typical) is 'assumed' to be about 30 to 50 years for Galvanized, depending on the local water and whether the pipe was imported or domestic. For cast Iron sewer pipes, somewhere between 40 and 80 years is expected; but the 80 year old ones disintegrate if you touch them!

Cheers,
Tom
 
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  • #25
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I'm not aware of any. Those comments (and those below) are from my personal experience/observation and that of a Maintenance Man I know that spends much time at an 80 year old building trying to prevent major floods.

Yes, increased flow (rust removal) can lead to holes in the pipe sooner rather than later; and of course higher pressure also leads to holes occuring sooner (higher pressure can push thru a thicker wall than low pressure. Just like a balloon!)

By the way, here in the USA nominal plumbing life (40psi typical) is 'assumed' to be about 30 to 50 years for Galvanized, depending on the local water and whether the pipe was imported or domestic. For cast Iron sewer pipes, somewhere between 40 and 80 years is expected; but the 80 year old ones disintegrate if you touch them!

Cheers,
Tom
My Galvanized piping is already 30 years. Iron rusts due to oxygen. If they are soak in water all the time, like in pipes with constant water in them. The oxygen source is only from water. So rusts took longer maybe the 30 years figure? I wonder if the titanic rusts from the salt water or oxygen in the water. What you think? In the literature, how many times slower galvanized iron rusts under water (or soaked in water) versus free air?

I guess i have to put plastic pipes outside the wall. Hmm..
 

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