Is EPDM for tank liner a catch-22?

[flyingcow]

I'm using the square tank you see in tarms website. PVC liner, works great,hx heat coils transfers heat very well(haven't hooked up the dom coil yet). Easy set up. I liked the idea of having to not watch my water ph(and yes its baking soda that will effect ph, or you can get a little better grade from pool supply house) and not having to be so careful about trying to stay below 170/175. If I had the option of using anything else, I would have located my storage in the garage and used an old S/S milk tank from a dairy farm. These will be discarded because of problems in the freon system developing a leak. But it will hold water and its S/S, no rust problems. They have a big cover so a man can enter from the top, easy access for coils.These tanks are designed to hold lquid and water is very close to the weight of milk. Call any installers of these and get put on a list for the old ones. 1000 gal tank will be about $1000. my .02

 

[mwk1000]

Thanks, STSS Manual says PH at 8.2-8.3 it is on the basic side as said here. Baking soda , if I remember my chemistry is a buffer to help keep the ph in a stable range. In any case , that is a big help since I still have my college text book and can look up the situation. I think the idea is to set the water with a base chemical ( all the base chemicals I know are nasty like lye,"drano", etc ), and then buffer it with sodium bi-carbonate. I'm not sure if the baking soda by itself will raise it up that much.

Know that I know what to aim for I can find a suitable additive, I'm pretty well versed in pH from my aquariums. I have all the test gear from that hobby.

 

[Fred61]

When I was electroless nickel- cobalt plating in another life, I used ammonium hydroxide to raise the pH of the baths where lime or sodium bicarbonate could not be used. I would goto a hot tub or pool store to get the chemicals.

 

[danmitchell9]

Neoprene looks good. 230F high end temp. Now if only I knew someone with a wetsuit factory.

 

[tom in maine]

There are a couple materials like Neoprene that are decent. They are expensive and are difficult to work with in sheet form.

All these materials have their pluses and minuses. There is always a balancing act between the cost/benefit of any given storage scheme or material.

As I mentioned, we have had good results with high temperature PVC's that we have custom run. It is more expensive than EPDM, but it is weldable,
field repairable (that is, patchable, in case someone attacks it with an ice pick or drill!) and we have liners that are over 25 years old in thermal storage applications.

PVC's age by loss of plasticizer. When you have a storage tank that is not constantly be flushed out with new water, the plasticizer stays in equilibrium in the water and the plastic
stays flexible. Even if it aged, it would become rigid, which is not an issue unless you need to move the tank. That is not a usual situation.

There is a lot of art that goes into producing a decent tank liner out of any weldable material, that is why there are not tons of them out there and most people use EPDM.
We hope to change that.

 

[free75degrees]

Hey Tom, would you be willing to sell a custom welded seam pvc liner if given a set of dimensions?

 

[tom in maine]

Right now, no. We are in the midst of making some changes and are working only with stock sizes.
If you have some time, we might be able to provide custom liners for folks in a couple months.

 

[Ugly]

too bad resin has gotten so expensive... high temp acid resistant Vinylester Resin runs about 180.00 for five gallons.... a thin coating bonded to light fibreglass or other mat is all that's needed to protect against water on a built in place concrete reservoir...keep in mind resins like that don't like the cold much and shouldn't be exposed to temps below -10c too often or they will begin micro fracturing...

 

[free75degrees]

Right now, no. We are in the midst of making some changes and are working only with stock sizes.
If you have some time, we might be able to provide custom liners for folks in a couple months.

Sure, I have time, probably a lot of time. I currently have epdm, but I regularly hit 180+ so I'll probably have to replace it some day. If you were willing to do it in a few months I would have to seriously consider doing it because I wouldn't want the opportunity to be gone when in a few years when I need a replacement.

 

[tom in maine]

I would not use aluminum in any plumbing situation. I have seen way too many weird electrolytic failures when aluminum is used in contact
with water and copper.

If you want to think about metal, how about copper flashing. It is more money, but it is copper!

I prefer polymer liners and copper heat exchangers. Both are serviceable and easy to work with and fairly easy to get.

 

[tom in maine]

Styrofoam will start to melt at 140F. Looks like a blow torch hit it over those temps.

 

[NHFarmer]

My tank is 7' in diameter, I used 4'x10' sheets of galvanized steel pop riveted together.The base is concrete and it is lined with EPDM. I feel that I will need to replace the liner at some point but I keep thinking that there must be a better way to make the tank waterproof without the EPDM.I am thinking that something like a spray on bed liner would work.I just don't want to be the Guinea pig

 

[tom in maine]

I am not sure I understand what the wood is doing. If you are asking about wood supporting a HX, no, use CPVC.

Extending surface tubing generally does not enhance heat exchange enough to warrant its extra cost. And it does have some impact on flow.

 

[tom in maine]

I would like to hear from people who have used EPDM that has been in service for five years or longer. Is there any degradation? What kind?
Effects on copper?

I suspect that everyone's fears about EPDM's premature failure are overstated. It does degrade, but no one is giving numbers.

My experience with EPDM is with solar products like Solaroll. It was a EPDM solar collector that deteriorated big time in service. It was permeable to oxygen.
Another one was Entran radiant floor tubing, which used EPDM. Similar failures.
This is not a similar use since these uses were under pressure and perhaps experienced some surface erosion.

 

[Der Fuirmeister]

How about aluminum flashing as a lining material? I once made a very simple wooden water trough lined with aluminum flashing. Each plank was faced with it and then silicone at the butt joints, screwed together, super simple. Could I make a tank this way, or is wood not suitable to take the heat?

not good unless you used all PEX tubing for the hx. Aluminum just reacts poorly with dissimilar metals.

 

[tom in maine]

Wood should be fine against the liner. I would prefer to use the foam as a buffer to protect the liner against any stray splinters or fasteners.

 

[thearvman]

This is my first post. This thread is fairly similar to my concern. I am installing a Tarm Solo 60 with 1200 gallon unpressurized storage. The tank liner is EPDM. The house is being renovated for infloor radiant heat. The basement is going to have a concrete over pour. We wanted to do this on the main floor also but the floor joists and hangers etc would not support the load. So we built the floor up with 3/4 plywood strips and aluminum transfer plates with pex running in the transfer plates. With concrete only the design water temperature was going to be in the 100 degree range now with the transfer plates it is going to be about 125 degrees. Planning to not heat the tank to above 175 and that a full load of wood in the tarm would raise tank temperature about 40 degrees then I only have a small window to fill the boiler again on very cold days. Is this a huge concern or not really because there are only so many super cold days and the tarm could be fired somewhere around 150 degrees ( in the storage tank ) safely because of the tank temperature continuing to drop while the boiler is being fired?

 

[tom in maine]

Hi,
It depends on the heat load of your building. The heat output of the radiant floor will be a function of what the floor covering is. It is likely that the only pinch point could be on really cold days, as you said. (Of course, we have had a whole month of this weather in Maine!) And then, the house might underheat slightly.
Check out www.builditsolar.com and look at the heat loss calculators.

That will tell you a lot. If the radiant floor is inadequate for the heat load, it can be supplemented with high output baseboard or radiant panels, to help you stretch to a bigger temperature differential from storage.

Welcome to Hearth.com

Tom

 

[thearvman]

Hi
Thanks for the quick reply. I have ductless mini split heat pumps also but the don't work when it is really cold. We are installing an electric boiler for backup ... It is not huge ... ie meant to keep house from freezing when on vacation. I am not sure if it could operate at the same time during really cold days.? I am not sure what you mean by high output baseboards and radiant panels. I do not really want to install any baseboard heat. What is a radiant panel? The guy doing the concrete over pour in the basement mentioned that we could do a 5/16 inch skim coat of some type of concrete product upstairs that would make the heat transfer better which would lower the design water temp of the system. I am not sure how much of a difference that would make.
Thanks

 

[tom in maine]

A radiant panel is like an old fashioned radiator, but it is made of steel and is wall hung. It puts out a lot of heat, like a mini radiant wall or floor.
www.qhtinc.com has them. They are available at most plumbing houses.
I suspect a skim coat might not function that well in boosting heat output on the floor. It depends how much is in contact with the tubing. 5/16" is pretty thin.
Thin radiant slabs are usually about 1.5-2" and completely encapsulate the tubing. An educated guess is that it will not function much better than what you were planning.

Radiant panels are small enough that they can be discreetly used and are not as ugly or obtrusive as baseboards.

 

[DaveBP]

The guy doing the concrete over pour in the basement mentioned that we could do a 5/16 inch skim coat of some type of concrete product upstairs that would make the heat transfer better which would lower the design water temp of the system. I am not sure how much of a difference that would make.

A professional radiant designer told me to never let concrete or cement tile setting mortar contact the aluminum heat transfer plates. They will corrode the metal. I've seen aluminium that was in contact with concrete. I believe him.

I would like to hear from people who have used EPDM that has been in service for five years or longer. Is there any degradation? What kind?

My experience with EPDM is with solar products like Solaroll. It was a EPDM solar collector that deteriorated big time in service. It was permeable to oxygen.
Another one was Entran radiant floor tubing, which used EPDM. Similar failures.

I think it's going to be difficult to reach a concensus on EPDM and its suitability for tank liners. EPDM is another one of those industrial materials that have been outsourced over the last couple decades. Most of it is made in China and India now. EPDM can be mixed with lots of different materials for different properties. It can also be cut with ground mineral powder just to cut costs. Some stuff out there labeled EPDM is over 50% ground stone.
What 15 or 20 year old EPDM did in service may not have a lot to do with what modern-sourced EPDM can be expected to do. Too many examples in the news lately of what a mess Asian quality control can be; and just how much some American corporations really care before they get caught.

I think there is probably still good quality EPDM out there but you'll need to do your research and ask for source certiticates if you can. You may not find it on Ebay.

 

[tom in maine]

DaveBP,
Both excellent points. If you were using the skim coat, you should not be using plates, they would be extraneous.

EPDM has a lot of variants out there. I hate to think that much of it comes from overseas, but have found that is the case with a lot
of polymers that we have researched.ARGH.
I am very skeptical of this type of material that is produced overseas. Quality is questionable and engineering support is not immediate.
I am still waiting to hear back from a company that responded to my initial query in November 2008. They needed to confirm something with the engineers in Formosa.
I don't think we will be doing business!

Fortunately there are still some manufacturers of these product here in the US and we can reach the right people with a simple phone call and speak English to them.

My experience with Solaroll, was not good. It was pulled off the market, for good reason. Entran was a different case, but spoke to the issue of formulations and additives.

All that being said. EPDM does work. I am certain that there are better quality versions of it. Who that is and where they are, I am not sure.
Tom

 

[pybyr]

Here are some leads I found - this product looks as if it is similar to Tu-Tuf, only a lot thicker.

If it is up to lining landfills, which it apparently is, then it ought to be up to the use for a heat tank
http://www.geocheminc.com/hdpealloy.htm
and they’ll apparently fabricate it into a pre-shaped-to-dimensions tank liner:
http://www.geocheminc.com/tank.htm
looks hard to beat unless the cost is insanely high- which I tend to think it actually may not be if people are using it for the applications that they describe.

If I did not already have some gorgeous already-fabricated stainless steel that is worth about as much as a roadworthy used car in the cellar, I’d be pursuing this membrane like wildfire- and I think that the “homemade tankage” thread from "Smee" in Maine represents the most elegantly simple DIY membrane support structure that I have seen yet- just that I would not use either EPDM or PVC

 

[tom in maine]

When it comes to plastic liners, you need to be over 20 mils thick. Anything under that is too permeable and water will migrate across the plastic. Add heat into that equation and it becomes more pronounced.

HDPE will not take the temperature. Polypropylene will, but it is rather stiff. These are both usually used as geomembranes and are used for large tanks, landfill or lagoon applications, which stiffness is a plus and handling is simpler than trying to do a small (500-1,000g) tank.

There are some options out there. They all have limitations. And unless you have used them for a very long time, you cannot necessarily believe everything that a salesman tells you! I am afraid I know that all too well.

At this time, even though there are some limitations, high temp PVC and some alloys utilizing it and EPDM are the ones that work well for this application.

As a DIY project, one can certainly site weld thicker PP sheeting for a liner.
I am intrigued but leery of truck bed liners. They could take the temp, but being sprayed on a tank and then exposed to the temps could cause differential expansion failures between the adhered liner and the shell.

 

[Fred61]

My tank is 7' in diameter, I used 4'x10' sheets of galvanized steel pop riveted together.The base is concrete and it is lined with EPDM. I feel that I will need to replace the liner at some point but I keep thinking that there must be a better way to make the tank waterproof without the EPDM.I am thinking that something like a spray on bed liner would work.I just don't want to be the Guinea pig

Well I'm going to be the guinea pig. I located a two part epoxy called water insensitive coating and if I can believe the sales person, it has been used on tanks at IBM and other industrial locations. It's rated for 320* wet. Check out the link below. This isn't the stuff I'm using but is interesting. I had a couple more links but I screwed something up when I posted them.

(broken link removed)