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Old 09-09-2012, 11:34   #31
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Quote:
Originally Posted by foggysail

Chick!

Geez, it sure helps to have a technical background!!! I share your thoughts but just never got around to look for potable tanks. Heck, I just Googled between posts and found there is a bunch of potable tanks out there for almost peanuts! By that I mean for less than $50.

Darn it though, they are just not stamped "marine use "

I have been putting off adding a tank to my current boat, after reading this thread I will look into installing one.

Plastic fittings--- We traveled this road before and of course you were correct then so ... I don't know what fittings are used in my boat other than they are plastic which hopefully I will change later to PEX.

Getting back to the OP, i still believe his best solution is simply to wire a pump pressure switch in series with his pump's 12vdc power. Of course it also requires plumbing it in series with his water line. I also don't see a need for high water pressure in my boat, I keep mine below 20psi.

Foggy
If I start with zero pressure (pump breaker off and pressure relieved), the motor for a few hours and it builds enough pressure to blow a hose off, how would a pump pressure switch help?
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Old 09-09-2012, 12:50   #32
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Re: High Fresh Water Pressure When Running Motor

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Originally Posted by phantomracer View Post
If I start with zero pressure (pump breaker off and pressure relieved), the motor for a few hours and it builds enough pressure to blow a hose off, how would a pump pressure switch help?

And you're heating the water with circulation from your engine? And your engine temperature is below boiling and of course boiling temperature increases with pressure?


I have seen similar problems with hot water tanks in a couple of our apartment buildings that get their heat from a hot water heating system boiler but you're not going to like the cause. In the cases I just mentioned, the boiler pressure started out at 0 psi the fresh water feed to the boiler turned off. Over time the boiler pressure increased even though the water feed to it was shut off. Next the boiler over pressure valve purged boiler water to reduce its pressure.

The cause was the high pressure potable water seeped into the boiler via leaking into the heating coils inside the hot water tank. AND WE WENT THROUGH 5 TANKS IN ONE BUILDING (in 7 years) AND 1 TANK IN ANOTHER BUILDING AND THE TANKS WERE STAINLESS STEEL!!!

And the high pressure potable water was set in one building to only 60psi so the problem was not caused by over pressuring!!! IT WAS CAUSED BY GALVANIC CORROSION!

So based on my shared experience, my guess is you have a failed hot water tank. Your engine's coolant is getting into your potable water and you may not notice it because the volume is small compared to the amount stored.

Foggy
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Old 09-09-2012, 13:33   #33
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Re: High Fresh Water Pressure When Running Motor

That is a possibility, though you would notice that the engine would overheat from loss of coolant. Plus the sweet taste of glycol antifreeze in the drinking water and resultant kidney failure would have been noticed by now.

In an apartment boiler, boiler pressure is probably 15 psig or so. Water pressure is oh anywhere from 30 to 80. so a cracked pipe causes the water to flow to the boiler, which then floods the expansion tank and pops the relief.

In a boat the same thing is more likely to happen. A cracked pipe in the water heater heat exchanger causes flow from the water heater to the engine, popping the 13 psig pressure relief in the radiator cap.

Sure starting at zero pressure its possible, but only till the water heater built up pressure to 11-13 psig. Above that the radiator cap pops vents to overflow. As the OP blew a hose off of the water system and did not vent coolant from the engine, we can deduce that the heat exchanger is fine.
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Old 09-09-2012, 13:50   #34
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Re: High Fresh Water Pressure When Running Motor

Quote:
Originally Posted by foggysail View Post
And you're heating the water with circulation from your engine? And your engine temperature is below boiling and of course boiling temperature increases with pressure?


I have seen similar problems with hot water tanks in a couple of our apartment buildings that get their heat from a hot water heating system boiler but you're not going to like the cause. In the cases I just mentioned, the boiler pressure started out at 0 psi the fresh water feed to the boiler turned off. Over time the boiler pressure increased even though the water feed to it was shut off. Next the boiler over pressure valve purged boiler water to reduce its pressure.

The cause was the high pressure potable water seeped into the boiler via leaking into the heating coils inside the hot water tank. AND WE WENT THROUGH 5 TANKS IN ONE BUILDING (in 7 years) AND 1 TANK IN ANOTHER BUILDING AND THE TANKS WERE STAINLESS STEEL!!!

And the high pressure potable water was set in one building to only 60psi so the problem was not caused by over pressuring!!! IT WAS CAUSED BY GALVANIC CORROSION!


Foggy
Nice. So by any chance was the heat exchangers in the stainless steel water heaters copper. My guess there is that the copper exchanger tubes and stainless tanks had a wee bit of electron interaction going on...

Though the same issue would happen with copper water pipe and a stainless steel heat exchanger without dielectric unions / flanges
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Old 09-09-2012, 14:10   #35
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Re: High Fresh Water Pressure When Running Motor

I still think controlling the amount of heated coolant flowing through the heat exchanger is the key to this. I have a similar problem when I heat water with my engine coolant, I don't blow hoses off fittings but when I open a faucet the water spurts out under higher than normal pressure and the water is dangerously hot. I've been thinking of installing valves so I can throttle the amount of coolant flowing thru the heat exchanger and see if I can keep the temp below about 140F. I guess given a long enough run, and it isn't that long, the water temperature gets pretty close to the coolant temperature. On my boat that's about 170F.

Sailorchick, you're the engineer here. What do you think? Reduce the flow of hot coolant through the water heater?
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Old 09-09-2012, 14:13   #36
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Re: High Fresh Water Pressure When Running Motor

Foggysail,

don't use a heating expansion tank. Yes, they look the same and the prices are vastly different, but the tanks for heating systems are not coated against corrosion, which mwans if you use them on fresh water, a) you will generate rust continuously, which tends to spoil your coffee, and b) you will develop a leak in a very short time.

Expansion tanks for domestic hot water are coated or have a bladder that encloses the fresh water completely and keeps it fresh.

Chick, seems like we come from the same industry - I've been building pumps for decades until I grew tired of it...

Oliver
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Old 09-09-2012, 14:28   #37
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Re: High Fresh Water Pressure When Running Motor

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Originally Posted by sailorchic34 View Post
That is a possibility, though you would notice that the engine would overheat from loss of coolant. Plus the sweet taste of glycol antifreeze in the drinking water and resultant kidney failure would have been noticed by now.

In an apartment boiler, boiler pressure is probably 15 psig or so. Water pressure is oh anywhere from 30 to 80. so a cracked pipe causes the water to flow to the boiler, which then floods the expansion tank and pops the relief.

In a boat the same thing is more likely to happen. A cracked pipe in the water heater heat exchanger causes flow from the water heater to the engine, popping the 13 psig pressure relief in the radiator cap.

Sure starting at zero pressure its possible, but only till the water heater built up pressure to 11-13 psig. Above that the radiator cap pops vents to overflow. As the OP blew a hose off of the water system and did not vent coolant from the engine, we can deduce that the heat exchanger is fine.
Well, there are some maybes here. Consider first why others do not have similar problems with their water heaters causing pressure build up just due to water expansion. Next, cracked pipes. No, the pipes were not cracked and it took a long time to nail down the cause of failures that are now well know to Weil-McClain who made both the boilers and most of the tanks. By the way, the construction of all the failed tanks were constructed with one the high pressure tank inside the low pressure tank (or visa versa). There were no coils commonly known for this purpose.

Now taste of anti freeze??? Maybe not! It would be such a small part of the total quantity of stored water. Further, not many people I know use their hot water for anything other than washing.

Consider pressure as you mentioned. Yes, I agree that the pressure would seemingly be insufficient to cause a hose to pop off. But as the number of times this occurs along with maybe a failed pressure cap for the cooling system, high pressures can build before although there would be higher engine temperatures.

Who knows what the actual causes are, as I stated, my analysis was just a guess. But again, if this is a normal situation caused by plain old water expansion from temperature increase, the solution would be all over boating forums.

Might be worth the OP to at least check the water in his cooling system. But if his cooling is done with raw water, then I am out of ideas.
Foggy
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Old 09-09-2012, 14:55   #38
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Re: High Fresh Water Pressure When Running Motor

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I still think controlling the amount of heated coolant flowing through the heat exchanger is the key to this. I have a similar problem when I heat water with my engine coolant, I don't blow hoses off fittings but when I open a faucet the water spurts out under higher than normal pressure and the water is dangerously hot. I've been thinking of installing valves so I can throttle the amount of coolant flowing thru the heat exchanger and see if I can keep the temp below about 140F. I guess given a long enough run, and it isn't that long, the water temperature gets pretty close to the coolant temperature. On my boat that's about 170F.

Sailorchick, you're the engineer here. What do you think? Reduce the flow of hot coolant through the water heater?
Reducing the flow rate, only delays the problem, but will not stop it. Force 10 makes a thermostatic valve that cuts the engine water off after the water heats up to about 140. Could do that with a two way or three way temperature control valve too.

Putting in a larger accumulator will reduce the pressure issue, A tempering valve or a thermostatic mixing valve ( better but $$) on the hot water heater discharge would keep the water at the sink safe.

Tempering valve L70A is the right one to get
http://www.watts.com/pages/_products...ls.asp?pid=717

Oh this is cool too
http://www.cashacme.com/prod_thermostatics_WHTC_kit.php
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Old 09-09-2012, 14:57   #39
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Re: High Fresh Water Pressure When Running Motor

Quote:
Originally Posted by foggysail View Post

Might be worth the OP to at least check the water in his cooling system. But if his cooling is done with raw water, then I am out of ideas.
Foggy
The water in a raw water cooled engine only gets to 120-130 maximum, with a 10 degree drop across the heat exchanger you would only get 100 to 110 degree water. does not work so well heating water and you would not have the pressure issue either.
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Old 09-09-2012, 15:01   #40
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Re: High Fresh Water Pressure When Running Motor

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Originally Posted by Oliver L. View Post
Foggysail,

don't use a heating expansion tank. Yes, they look the same and the prices are vastly different, but the tanks for heating systems are not coated against corrosion, which mwans if you use them on fresh water, a) you will generate rust continuously, which tends to spoil your coffee, and b) you will develop a leak in a very short time.

Expansion tanks for domestic hot water are coated or have a bladder that encloses the fresh water completely and keeps it fresh.

Chick, seems like we come from the same industry - I've been building pumps for decades until I grew tired of it...

Oliver
+1

I've used a lot pumps over the years. All types and sizes, well up to heavy commercial / high tech anyway. Even engineering gets boring after a while. Tough I still love problem solving...
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Old 09-09-2012, 15:55   #41
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Re: High Fresh Water Pressure When Running Motor

Quote:
Originally Posted by sailorchic34 View Post
That is a possibility, though you would notice that the engine would overheat from loss of coolant. Plus the sweet taste of glycol antifreeze in the drinking water and resultant kidney failure would have been noticed by now.

In an apartment boiler, boiler pressure is probably 15 psig or so. Water pressure is oh anywhere from 30 to 80. so a cracked pipe causes the water to flow to the boiler, which then floods the expansion tank and pops the relief.

In a boat the same thing is more likely to happen. A cracked pipe in the water heater heat exchanger causes flow from the water heater to the engine, popping the 13 psig pressure relief in the radiator cap.

Sure starting at zero pressure its possible, but only till the water heater built up pressure to 11-13 psig. Above that the radiator cap pops vents to overflow. As the OP blew a hose off of the water system and did not vent coolant from the engine, we can deduce that the heat exchanger is fine.
makes sense. It only happens on long engine runs (6 hours+) never happens (yet) on 0-5.999 hour runs. Happened on a 2 8 hour runs and one 6 hour run.

I am sure if the coolant was being fed into the hot water tank, that it would take a lot less than 6 hours to build that pressure. Just seems slow but surely, the hot water pressure builds. zero taste in the water and zero antifreeze missing after hundreds of hours motoring the last couple seasons.

more importantly no extra antifreeze in the motor either. SEEMs like the water and coolant are still separate.

Paul
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Old 09-09-2012, 16:35   #42
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Re: High Fresh Water Pressure When Running Motor

" Force 10 makes a thermostatic valve that cuts the engine water off after the water heats up to about 140."

That's the answer. It would act just like an electrical thermostat and shut off the source of heat at a set point.

Sailorchick, a friend of mine is a hydrologist in Everglades National Park. He designs systems to control the flow of water through the park. He has shown me some of the structures that do this. They are equiped with huge pumps that have discharges about three feet across. I asked him what kind of pumps they were. He said he didn't know. He just told the engineers how many millions of cubic feet of water he wanted to move and how fast he wanted it done. They had to figure out how to do it. Of course now I have to get into one of these things to see what makes it go. I'm guessing they are pretty simple. Something like a propeller in a pipe.
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Old 09-09-2012, 17:19   #43
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Re: High Fresh Water Pressure When Running Motor

Probably vertical turbines with a few larger turbines. in series. Pumps, well the bigger ones have a pretty complicated impeller and volute design. wear rings, bearing life and lubrication, shaft seals, etc..

Gee are they still trying to drain the swamp. Though I'm guessing they are trying to fill it now.

Spent a day or two anchored in the little shark river down by point sable on the west coast years ago. Pretty, but a little buggy.
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Old 09-09-2012, 18:06   #44
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Re: High Fresh Water Pressure When Running Motor

"Though I'm guessing they are trying to fill it now."
Exactly right.
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Old 10-09-2012, 10:24   #45
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Re: High Fresh Water Pressure When Running Motor

Thanks everyone for the input. So I think the first thing that is needed is the relief valve.

The valve WATTS Relief Valve, 1/2 In, Brass, M x FNPT - Relief Valves - 1X624|530-1/2 - Grainger Industrial Supply should blow before a clamped hose comes off I assume! So I would just T it into the line from the hot water tank, drain to the bilge.

Have to scout out on the boat where I can put the tank ProFlo Thermal Expansion Tank 2 Gallon - FreshWaterSystems.com on the boat.

what pressure should the tank be set at?

Thanks again!

Paul
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