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Old 08-22-2012, 10:44 AM   #29
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Doug, I like your water softener idea.

I still think from a saftey and maintenance viewpoint a small expansion tank is needed for this application. The tank is designed to provide an air cushion automatically and is a device that provides the reliability needed to correct this potentially dangerous situation.

I look at the end result of an pver pressureized hot water system and see the possibility of a joint failure and an open ended line spraying scalding water and possibly injuring someone.

If anybody wants the info, I will spec an expansion tank and describe an installation process.

Adios,
Dan
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Old 08-22-2012, 12:37 PM   #30
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Ok, another dumb question, does the leak problem only show up with electric operation or with gas also? Doug k's response certainly indicates he has only seen the problem on electric.
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Old 08-22-2012, 12:45 PM   #31
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Rick, there are no dumb questions. I don't know... It seems like the electric element is set to a higher temp though. The real problem here is the very limited expansion space.

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Old 08-22-2012, 01:03 PM   #32
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Originally Posted by danlehosky View Post
Rick, there are no dumb questions. I don't know... It seems like the electric element is set to a higher temp though. The real problem here is the very limited expansion space.

Dan
Sort of. The problem is it's a recreational trailer water heater planned for relatively short term use, therefore a limited expansion place within the water heater is provided. On longer trips (we were out six months) the air in the expansion space is absorbed by the water, hotter in the combo units.

A complication is that RV parks use a backflow preventer valve that makes the RV have a closed loop system; when the water heats up it expands and increases system pressure.

Another factor is the new Atwood combo heaters probably reach water boiling temperature, say overnight, or at higher altitudes when a faucet is opened and the pressure is suddenly released. There is a "shot" of steam produced in the heater forcing some steam and air out of the heater pressure relief valve. The result of this is less air expansion space, each time it happens, and it can happen a lot if you leave the electric function switch on steady. I shut mine off at bedtime and that takes care of it. We have never had water leakage because of it, but I don't like steam/air/water "burping" out of the pressure relief valve during the night.

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Old 08-22-2012, 01:22 PM   #33
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Doug,I hear what you're sayin but I disagree that something should be designed for "limited use".

Maintaining an air bubble when travelling and water is shloshing around is difficult. Opening the T&P valve is not the best idea as you can be scalded with hot water and these are installed as a limiting device and not for maintenance.

There was a post on this thread comparing checking your tire pressure and wear with maintaining this air bubble. I think it's a poor example. Tires can be visually inspected and signs of wear and underinflation are easily observable.

I also don't buy the limited use arguement. You use yours extensively and should have the protection afforded by a properly designed system that incorporates the proper safety devices to make your experience risk free.

Expansion tanks are designed for this very purpose and the addition of one would cost very little.

Doug, I know you maintain your trailer well and understand how to keep your system functioning properly but this expansion should be compensated for automatically and not be viewed as a maintenance item

I really think AS should take another look at this and make some design changes that will make this system much safer

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Dan
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Old 08-22-2012, 02:01 PM   #34
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The pressure relief valve at the hot water heater is 125psi, the pump puts out 45psi and the incoming shore water is limited to 65psi. You are over pressurizing the water system 100% (double) the factory design of 65psi. BY CURRENT DESIGN and WARNINGS the significantly higher temperature/pressure of the new XT series water heater will constantly stress the water system with every heating cycle.

There are two glaring views or “camps” present here:

The first is the George R.R. Martin camp: “Most men would rather deny a hard truth than face it.”. The few who were fortunate enough to purchase perfect airstreams and are staunchly adamant that there are no issues with the Airstream that are not directly attributed to the owners lack of experience, proper maintenance and proper operation of the Airstream.

The second is the Ben Franklin camp: “An ounce of prevention is worth a pound of cure.”. Those of us who see simple fixes to design issues of which I whole heartedly subscribe, always have.

While one could argue the point of “design flaw”, one cannot honestly argue “design deficiency”. While I personally decided to replace the water heater with a premium product to go with my premium trailer the over pressurization problem as stated/cautioned by Airstream and explained by others could have been/can be solved with a $25 bypass valve or expansion chamber and moreover should be! Why would you want to run the risk of needing to replace a rotting floor in the coming years? This seems to be a predominate issue with the Airstream product and it appears that the constant repeated over pressurization cycles of the hot water heater could be most of the problem. I just can’t believe you would not want to protect your 60K investment with a simple inexpensive fix! Why tell everyone to simply follow the air cushion procedure, open a faucet repeatedly during each and every heating cycle, turn it off when not in use etc.?

How many of you actually pressure relief the system every time the hot water heater is heating? Really! In twenty years of trailering I have not once and will not need to in the future.

I do not understand the constant denial and blind loyalty to the Airstream brand by some any more than some believe I am just an anal Airstream basher. To each his own, but at least no one will be able to say “I was not warned”.

I love my trailer but there are issues, (“opportunities for improvements” for the other camp) with it that should not be there period. They are areas that even Airstream warns you about that could be solved by simple improvements.

After having the proper use of the hot water tank explained to me over and again I am more adamant that the problem should be solved not worked around by constant “baby sitting”.

Dan has graciously offered design help and I am happy to loan anyone my PEX tool with free return UPS label included should anyone want to put the bypass valve or expansion chamber in. Location will be important to make sure you have access/room to use the tool. Mine being under the bed was a perfect spot.

However, it should be done by the factory for anyone that has the newer XT water heaters. Just saying
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Old 08-22-2012, 02:05 PM   #35
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My Airstream manual says my trailer is designed for recreational use only, not for full-time living. I suppose that's why the RV manufacturers consider the Atwood heater adequate. I'll buy that, do the extra steps for long trips. No more risk here than many, many RV'ing procedures we do if done improperly.

My sense is that the conditions that cause the leaks we are talking about here are not unique to the combo elect/propane unit. My sense is that people frequently have internal water leaks from high pressure they simply don't realize, old and new Airstreams and almost everything else in the park. These are closed water systems are subject to conditions mentioned in this thread that will cause internal leaks from time to time.

You just won't know it, and many times there will be no harm done. It is important to inspect regularly for evidence of leaks, as well as many other issues. More important I believe than trying to engineer a bullet-proof Airstream, which of course will have it's own issues, not the least of which is large up-front expenditures that may be unnecessary.

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Old 08-22-2012, 02:59 PM   #36
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Doug, I am installing a 2 gallon expansion tank that will allow me to enjoy my recreational time without stressing about where my pressure is at in my potable system. Total cost....... 63 dollars.

I simply cannot understand your and Airstreams argument that defining a use as recreational should change the commitment to established standards. I'll be very disappointed if AS does not address this issue.

However, I am done with it. I made a change in my system piping that should have been been done as part of the manufacturing process. I should not have to deal with "value engineering" practices. My system is now properly protected and adequate for the purpose intended.

Adios,
Dan
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Old 08-22-2012, 03:26 PM   #37
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Dan,

A 2 Gallon tank is pretty large especially for as often as I winterize. Had I not replaced the heater I was planning on installing a Jandy Laars Lite2 / Legacy Pool Heater Pressure Relief Valve 75 PSI P/N: R0040400 on eBay for $50 into the vertical or two horizontal cold water lines right at the hot water heater and push the drain line out the same opening in the floor as the drain valve line. You would only need to make one cut install a SharkByte tee, two SharkByte adaptors to connect the pressure relief valve, some ĹĒ PEX line and or hose for drain. This protects the system from any over pressurization. Thoughts?

I might just do this anyway.
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Old 08-22-2012, 03:33 PM   #38
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engineer a bullet-proof Airstream
doug k
Not "bullet-proof" just reliable and more importantly not self destructive if your forget to do the all-important hot water over pressurization safety procedures as recommended by Airstream and Atwood.
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Old 08-22-2012, 03:52 PM   #39
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I guess my question was really dumb. No responses. The reason I asked was kind of answered by Doug. These are closed systems, right? The only flow control devices are outside of the rv unit. So if I am thinking right, the water pressure increases to the pressure at the water heater, if its 100 psi there its 100 psi everywhere, hot or cold. My relief valve on the water heater is 150 psi. Atwood recommends, as one of their permanent solutions, putting a 125 psi relief valve in the cold water inlet. If thats a permanent solution, why not just put 125 psi valve in the hot water tank? Am I over simplifying this? Does anyone know the water pressure in the lines when everything is correct (ie. right air bubble in water heater)? Thanks for the answers to my dumb questions.
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Old 08-22-2012, 03:55 PM   #40
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Howard, I had it in the shop....... Bring on those pressure fluctuations... I like the on demand too. If we end up using our trailer as planned this will be what I will eventually install. Why not bulletproof????

Dan
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Old 08-22-2012, 04:25 PM   #41
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I guess my question was really dumb. No responses. The reason I asked was kind of answered by Doug. These are closed systems, right? The only flow control devices are outside of the rv unit. So if I am thinking right, the water pressure increases to the pressure at the water heater, if its 100 psi there its 100 psi everywhere, hot or cold. My relief valve on the water heater is 150 psi. Atwood recommends, as one of their permanent solutions, putting a 125 psi relief valve in the cold water inlet. If thats a permanent solution, why not just put 125 psi valve in the hot water tank? Am I over simplifying this? Does anyone know the water pressure in the lines when everything is correct (ie. right air bubble in water heater)? Thanks for the answers to my dumb questions.
Mike, I'll take a stab:

When I spoke with Airstream they stated it was 125psi but I did not look and perhaps they were thinking of the old lower temperature design. It would make sense that it needs the higher pressure to reach 160 degrees. If it is actually 150psi that is much worse than I thought. If the pressure relief valve at the hot water heater is lowered it might cause real problems with the higher temperature heating design. If a secondary lower pressure relief valve is placed in the hot water line than you would lose hot water not cold, safety? If the incoming pressure is limited to 65psi by Airstream I would think 75psi would be plenty of head room for the secondary, but maybe that is not high enough for the water to heat to 160 degrees. Maybe you do need the expansion tank as Doug suggested but does that mean there is still 120psi in the lines? A hot water tank expert needs to chime in or maybe a discussion direct with Atwood.

The issue for me was 100% resolved with the installation of RV-500. It only heats when the water is flowing at static pressure which should never be above 65psi.

When mine was leaking under the sink the hot water pressure relief valve was also leaking. So if it is rated at 150psi would it not be 150psi at the sink? Ironically this is also the pressure Airstream said they test the trailer to. This seems like a hell of a lot of pressure for a small closed loop system.
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Old 08-22-2012, 04:32 PM   #42
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I guess my question was really dumb. No responses. The reason I asked was kind of answered by Doug. These are closed systems, right? The only flow control devices are outside of the rv unit. So if I am thinking right, the water pressure increases to the pressure at the water heater, if its 100 psi there its 100 psi everywhere, hot or cold. My relief valve on the water heater is 150 psi. Atwood recommends, as one of their permanent solutions, putting a 125 psi relief valve in the cold water inlet. If thats a permanent solution, why not just put 125 psi valve in the hot water tank? Am I over simplifying this? Does anyone know the water pressure in the lines when everything is correct (ie. right air bubble in water heater)? Thanks for the answers to my dumb questions.
That's my thinking. Why would you not just replace the existing valve with a lower psi valve. Hopefully someone else will chime in and answer it.
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