Hot Water PVC Hose - Temp Ratings

[Maine Sail]

[FONT=Verdana, Arial, Helvetica, sans-serif]Here's a question for the group. I have already posed this question to both Jim the product manager of Shields hose and to Trident hose and neither have a solution other than to suggest a an FDA approved PEX tube.
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[FONT=Verdana, Arial, Helvetica, sans-serif]#1 Find me a small marine engine that runs at a nominal operating temperature lower than 145-150 degrees?
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[FONT=Verdana, Arial, Helvetica, sans-serif]#2 Now find me an FDA approved potable water hose [/FONT][FONT=Verdana, Arial, Helvetica, sans-serif]that has a max working temp above 150 degrees that is [/FONT][FONT=Verdana, Arial, Helvetica, sans-serif]made of nylon reinforced PVC. this is the type installed on most production boats for potable water.

#3 Find me even a hand full of production boat builders who offer, as standard equipment, a way to control the temp of the water heater when it is running off the engine?
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[FONT=Verdana, Arial, Helvetica, sans-serif]Here's the rub..[/FONT]

[FONT=Verdana, Arial, Helvetica, sans-serif]The water heaters in boats will eventually heat to the engine's running temperature if run long enough. There is no means, on any production sail boat water heater I have ever seen, to temper the water temperature as it reaches a pre-determined max set temp other than when it is running off 120 volts. I have seen mixing valves used but not very often and usually only on high end/ high dollar vessels.

With a residential indirect fired water heater the aquastat is set at your desired temperature and the aquastat subsequently turns on or off either a zone valve or a circulator to direct boiler water to the indirect fired water heaters coil. When the water reaches the max set point the aquastat breaks and stops the circulator or zone valve from over heating the water in the heater. Most marine water heaters, at least in production boats, are not plumbed this way and when the engine runs the coolant flows until the water heater is the same temp as the engine unless you add a mixing valve..

On our boat the engine runs at 180 degrees. Most PVC FDA rated water system hose has a max temp rating or between 140 & 150 degrees yet the builders have failed to catch on to this dangerous mismatch or address high & potentially dangerous temps in water heaters and the low temp ratings of the hose builders are connecting to it.
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[FONT=Verdana, Arial, Helvetica, sans-serif]Numerous builders still use 150 degree rated hose on 180 degree potential systems???
How safe is this? How safe is 150 degree + hot water for that matter? Not very according to Jim the product manager at Shields Hose who I ran the scenario by. Not only will max working pressure be reduced as temps rise but the hose gets so soft that it can rupture. 180 degrees is enough to scald and burn...[/FONT]

[FONT=Verdana, Arial, Helvetica, sans-serif]Am I off on my thinking here that this is a potentially unsafe mismatch?? I am in the process of converting our current boat to PEX tubing after having a hot water supply hose blow right off the water heater on our last boat and discovering this temp mismatch.

Perhaps Peggy can offer her insight..
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[FONT=Verdana, Arial, Helvetica, sans-serif]Just thinking out loud...
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[Stu Jackson]

Our tractor engines (Universal)

have two different thermostats available, 180 and 160. While many have claimed that salt will drop out at the lower thermostat setting, I've used both and neither seems to get the water that hot, because it is a hreat transfer which is not 100% efficient. Just guessin'...

 

[Maine Sail]

have two different thermostats available, 180 and 160. While many have claimed that salt will drop out at the lower thermostat setting, I've used both and neither seems to get the water that hot, because it is a hreat transfer which is not 100% efficient. Just guessin'...

Stu,

I have measured 165 degree water coming out of my faucet with my infrared. Westerbeke insists that my engine run with a 180 stat and with 2800 hours and zero issues I think I'll stick with it.. These heaters are small capacity and if the engine is run long enough, and the faucet not cracked, they will eventually surpass the PVC hoses temp rating. We sometimes have to motor for a while in zero wind and the water does get hot, very hot..

 

[Bill Roosa]

Put a valve on the anti loop

Pretty simple solution. Cut the heater line to the hot water tank and put a ball valve in. Turn the valve off once the water heater is up to temp.

Sometimes the manual solution is the only solution.

I'm also sure that you could rig a thermostat sensor from an auto to a simple control circuit that controls a solenoid that will turn the valve on and off for you. I can show you how to construct the control circuit once you have the temp sensor BTW.

 

[Ross]

Re: Put a valve on the anti loop

Domestic hot water above 120 degtrees F. is dangerous. Somewhere there must be a 12 volt control that will solve this problem. As for hoses commercial food processors routinely use near boiling water for plant cleaning and have FDA approved hose to handle it.

 

[Don S/V ILLusion]

Re: A Riddle

Although there may be examples, I am unaware of any systemic problems caused by this scenario. Given that this hose is commonly used on boats and there is no rash of failure, what's the real issue?

I can only assume the rating is conservative both in temperature and pressure and the lack of readily available hose with which to replace it would indicate the lack of a market for it - this would seem to bear out that it's a non-problem.

 

[r.w.landau]

Maine Sail, Rehau pex will work to 200 degrees.

Here is an excerpt from their literature.
RAUPEX UV Shield pipe is rated for continuous operation of 160 psi @ 73.4°F (1105 kPa @ 23°C), 100 psi @ 180°F (690 kPa
@ 82.2°C) and 80 psi @ 200°F (550 kPa @ 93.3°C). It is compatible with brass crimp ring fittings certified to ASTM F 1807,
RAUPEX compression nut fittings, and EVERLOC compression-sleeve fittings certified to ASTM F 2080 and CSA B 137.5.
http://na.rehau.com/
r.w.landau

 

[sailingdog]

But is it approved for POTABLE water use???

Here is an excerpt from their literature.
RAUPEX UV Shield pipe is rated for continuous operation of 160 psi @ 73.4°F (1105 kPa @ 23°C), 100 psi @ 180°F (690 kPa
@ 82.2°C) and 80 psi @ 200°F (550 kPa @ 93.3°C). It is compatible with brass crimp ring fittings certified to ASTM F 1807,
RAUPEX compression nut fittings, and EVERLOC compression-sleeve fittings certified to ASTM F 2080 and CSA B 137.5.
http://na.rehau.com/
r.w.landau

 

[sailaway78]

Down and dirty

Maine,
I am assuming that you are talking about the water supply hose from the heater to the faucet, and not engine to heater. My first and foremost thought, would be to be sure and turn the water pump off, and not leave pressure on the system. While this would not totally alleviate the problem it would keep the pressure off, and greatly reduce the risk of a hose failing. As a general rule, I leave the pump off anyway when not using water. Of course my Yanmar is raw water cooled, and doesn't run at that high a temp.

 

[dwain6805]

Simple-

Add a thermostatic tempering valve. My IsoTemp 11 gallon heater has one from the factory. The result is tempered water before it hits the hose.
Dwain

S/V Dancy
KP 44 #279

 

[Maine Sail]

But is it approved for POTABLE water use???

Rehau offers both potable water and hydronic PEX tubing for radiant use. I used to sell Quest and Wirsbo years ago but only for radiant but they now all have potable water certifications as well..

 

[Maine Sail]

Maine,
I am assuming that you are talking about the water supply hose from the heater to the faucet, and not engine to heater.

This is correct..

My first and foremost thought, would be to be sure and turn the water pump off, and not leave pressure on the system. While this would not totally alleviate the problem it would keep the pressure off, and greatly reduce the risk of a hose failing.

I now do this after my incident in 2005...

As a general rule, I leave the pump off anyway when not using water. Of course my Yanmar is raw water cooled, and doesn't run at that high a temp.

Some RWC engines run at temps as low as 155-160. While I don't believe this to be a big failure problem the potential is certainly there especially as the hoses become older and or maintenance has not been kept up with..


I think the bigger problem is the water temp at the faucet if you are not careful as both my wife and I have turned our hands quite red before..

Add a thermostatic tempering valve. My IsoTemp 11 gallon heater has one from the factory. The result is tempered water before it hits the hose.
Dwain

S/V Dancy
KP 44 #279

This along with the PEX is the route I am going with mine. Unfortunately there are thousands of heaters out there running unrestricted..

 

[dwain6805]

A tempering valve

will reduce the temp of the water at it's outlet. Standard equipment in nursing homes, hospitals, solar heaters and Isotemp marine heaters.
Also called a mixing valve, it's a solution to scalding water temps. Installed at the heater output, it reduces the hot water temp before it reachs the hose, and faucets. A byproduct of this is it will increase your hot water volume by diluting it with cold before it gets to you.
Dwain

 

[Benny]

Re: A Riddle

The solution is very simple; I'll use whatever hose is rated to handle the temperature and will not worry if it is FDA approved potable. I use my hot water to shower and not to prepare tea or cocoa.

 

[sand sailor]

Re: A Riddle

try a heat exchanger and a mixing valve ? you can adjust it to the temp you want

 

[Scott B]

But is it approved for POTABLE water use???

From the PPFA ( plastic pipe an fittings association) website FAQ.

PEX tubing can be used up to 200° Fahrenheit for heating applications. For plumbing, PEX is limited to 180° F. Temperature limitations are always noted on the print line of the PEX tubing.. PEX systems are tested to and can be used with standard T and P relief valves that operate at 210” F and 150 psi.

 

[Scott B]

[FONT=Verdana, Arial, Helvetica, sans-serif]Am I off on my thinking here that this is a potentially unsafe mismatch?? I am in the process of converting our current boat to PEX tubing after having a hot water supply hose blow right off the water heater on our last boat and discovering this temp mismatch.[/FONT]

[FONT=Verdana, Arial, Helvetica, sans-serif]Perhaps Peggy can offer her insight..[/FONT]


[FONT=Verdana, Arial, Helvetica, sans-serif]Just thinking out loud...[/FONT]

I guess Hunters not so cheap after all..... all the new boats come with PEX already installed

 

[Maine Sail]

My question...

My question is more of a "why" do builders do this, rather than what is the solution.

While there are many solutions including mixing valves, a bypass valve or FDA PEX tubing I was more wondering why boat builders allow & contunue the construction of boats with water heaters that can reach engine operating temp and then on top of that they slap on a hose not rated for that temp ??

It seems awfully strange to me that in 2005 I could buy a boat with an unregulated water heater and hose that is not rated for the potential temps. While I fully understand that quality water heater makers such as IsoTemp include a mixing or tempering valve the cheap "low buck" makers do not and the builders usually do not add them either?

How can the standards currently allow this? Shouldn't a means of controlling water heater temperature, when running off the engine, be a standard requirement just as it is in your home?

 

[BobM]

Re: A Riddle

Regarding potable, keep in mind that most folks don't drink hot water out of the tap anyway.

For plastic hoses, FDA's definition of potability likely has a lot to do with the amount of plasticizers that will come out of the hose. The more rigid the hose, the less plasticizers are in it typically. The hotter the water and the longer a quantity of water is in the hose, the more leachables you get.

Long story short. You all should let your water run for a moment if you have plastic tubing so you aren't drinking water more saturated with leachables from the tubing. Regarding your hot water Mainesail, when you replace the tubing I suggest you get it up to temp a few times and flush it out to get what is likely to be a higher inital quantity out of the tube.

Regarding the high temperature? Plan on replacing the hose fairly frequently as it will likely get brittle. Note that how you treat your potable water can impact it as well. If you use bleach to treat your water it may have an impact. I use bleach, because I trust its sanitizing ability but I don't drink the potable water. I really just wash dishes with it.

 

[garylinger]

Re: A Riddle

I don't know about all of the S2 models but my 1980 9.2C has copper hot water lines leading from the water heater to the faucets.