Hot Water Plumbing Issue Help

 
Waswood
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Post by Waswood » Fri. Oct. 28, 2016 12:08 pm

Well it's that time of year again to start up the stove. I have been burning a few wood fires to knock off the night chill. My stove heats 100 gallon (2-tanks) of water and I turn the electric off to hot water heater. My problem is it will occasionally blow off hot water when the temp gets to 210. I have it hooked up as a gravity system with no pumps .the tanks are set up on stands in basement next to the stove and cold goes in the bottom and hot out the top back to the top of the water tank. I was looking for submersible pump that would act as a sub pump to pump out the hot water when it does dump. I call my local store and they tell me to add an expansion tank above the tank and that will solve the issue he thinks. I'm on well water and there's already a tank . Can anyone help me with this problem? As it stands I have a water alarm in a 5 gallon bucket that will alarm when the tank dumps and that's usually in the middle of the night so I get up and go dump it. I notice it happens more when burning wood due to the open flame I guess. Coal only does it when its real cold and its burning hot. I like the ideal of the stove heating my water but I'm not sure it's worth it. Any ideals?
Last edited by Waswood on Sat. Apr. 01, 2017 11:54 am, edited 2 times in total.
Reason: Moved to Venting, Plumbing, Chimneys, Controls, Coal Bins


 
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pintoplumber
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Post by pintoplumber » Fri. Oct. 28, 2016 12:26 pm

Can you pipe your relief valve to the outside? Dennis

It's dumping on temperature not pressure. An expansion tank isn't the solution.

 
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lsayre
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Post by lsayre » Fri. Oct. 28, 2016 6:42 pm

I didn't know that pressure relief valves blew on temperature. Wouldn't they call them temperature relief (or perhaps "dump") valves if that was the case?

 
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Lightning
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Post by Lightning » Fri. Oct. 28, 2016 7:05 pm

I believe they dump on either/or. If either pressure gets too high or temperature gets too hot.

Waswood, did you post this last year or some point in the past? This seems familiar.

 
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davidmcbeth3
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Post by davidmcbeth3 » Fri. Oct. 28, 2016 7:50 pm

Can you put in an automatic valve that would stop the water?

 
Waswood
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Post by Waswood » Sat. Oct. 29, 2016 12:15 am

Yes I did post this last year. I changed some plumbing so both tanks were in the circuit to be heated instead of just preheating the water in 1 tank. The valve blows off on pressure or temp 210 I believe it is. The whole set up is in the center of my basement and can't gravity it outside . That's why I was thinking I could find a sub pump that I could put in my bucket and let it pump it outside but the ones I found are $$. I can't see paying another $500 for the pump. Midaswell just use elect to heat the water. Although I don't like that ideal when I can use the stove.

 
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Lightning
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Post by Lightning » Sat. Oct. 29, 2016 3:55 am

Home Depot sells little sump pumps that will fit right in a five gallon bucket. I have one in my basement. I use one like this, it's less than $100.

http://m.homedepot.com/p/Superior-Pump-1-2-HP-Submersible-Thermoplastic-Sump-Pump-92572/204610256


 
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Post by Freddy » Sat. Oct. 29, 2016 5:37 am

How much water dumps when it does dump? Even though you have a well tank it may be dumping on pressure. The well tank has a back flow in it & perhaps it can not expand backwards into the tank, or, if the water pump just shut off, there may be very little expansion room left. Have you measured the temperature to see if it's actually 210? Is there steam in the air when it dumps? My gut says it would take a lot of fire to boil 100 gallons. It could be done, but that's a lot of heat. Is there a temperature/pressure blow off valve on each tank? There should be. Thing happen real fast if water boils.

Maybe add 12 feet of baseboard heat? That would gravity off extra BTU's.

Maybe shorten the coil in the stove?

 
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Post by plumberman » Sat. Oct. 29, 2016 6:12 am

going with pintop, plumb the outlet end to outside of basement. drill/tap nearby waste line and plumb in is also another choice. :idea:

 
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Post by Richard S. » Sat. Oct. 29, 2016 6:15 am

First thing I would do is put a psi/temp gauge on the water tank so you know what is going on. You have just a short coil going through the stove? I would look at ways to lower the heat. If it's consistently that high use some finned radiation on the hot end of the coil feeding the tank to bleed off some heat, no sense dumping it down a pipe. ;) Shorter coil, deflector of some sorts etc. may be other option.

You have a T&P (temperature and pressure)relief valve, it will go off when the temp hits 210. You can replace it with pressure only valve but with those high temps that might be safety issue, also keep in mind some of the things in your house may not be designed to handle water that hot like the dishwasher. If you don't have mixing valve get one. If you go with pressure only valve keep an eye on the system pressure gauge and make sure expansion caused by the hot water tank is not driving it above 60psi.
Waswood wrote:I call my local store and they tell me to add an expansion tank above the tank and that will solve the issue he thinks. I'm on well water and there's already a tank .
We have ours set to cut off at 60psi, that's the highest it should be AFAIK. If it's pressurizing the system above 60 lower it. If it's going up to 60 or expansion from the hot water tank is driving it above 60 after the well pump ran a quick fix here may be lowering the cutoff to 55 or a little lower.

Never occurred to me but I guess the well tank would act as expansion tank however if the well pump just ran there may not be much room for expansion. I would check this as well, drain the water out of the system and tank. It should sound hollow If you hit the side of it. If it sounds like there is water in it then it may be toast. Test the pressure on the tank while you have it drained. It should be a few PSI below the cut in pressure on the regulator.

 
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Post by pintoplumber » Sat. Oct. 29, 2016 8:18 am

There should be a 75 psi relief valve at the well tank to protect the tank in case the pressure switch doesn't shut the pump off. If there's a check valve, it would be on the pump side of the tank. The relief valve at the tank would be leaking if it's going off on pressure.

It's hard/expensive to find a sump pump rated for higher than 140 degree water. Dennis

 
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Post by bobok » Sat. Oct. 29, 2016 8:47 am

A T&P valve is not supposed to regulate pressure. It is only a SAFETY valve. A picture of this setup would help. Is the pressure tank an old fashioned tank with no bladder? If it is water-logged you could be getting a spike when the pump comes on that in turn trips the t&p. How big are the pipes to the tanks? Does the hot water thermo siphon quick enough to prevent the top of the tanks from reaching 210 while the bottoms are still cool? temp guages on the supply and return would tell. Finally a T&P that blows off frequently will soon leak on its own and need replacing. Pictures, pictures, pictures ;) BoboK

 
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Post by Waswood » Sat. Oct. 29, 2016 5:44 pm

I will ty to get some pics when I get time . Working 16hrs a day now for a couple more days. The water that comes out is very hot maybe a little steam . Only the tank closest to the stove releases water not the 2nd tank. Both have a T&P valve on top. Their are temp gauges on the top pipes stove to 1st tank , 1st to 2nd tank and bottom cold side tank to stove. When it blows off the top stove to 1st tank is over 210 and the bottom maybe 150 ish. The t&p valve is very close to hot coming from stove but that's the only place I had to put it. Note the bottom of both tanks are tied togeather then go back to the stove. There is a mixing valve where the hot water goes up to the house . I do believe it's temp not pressure that's causing the issue. I was thinking a cir pump to better balance the tank temp but didn't want to have something in the system using elect and just something else to fail? Thank you for the input and ideals.

 
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Post by blrman07 » Sun. Oct. 30, 2016 6:44 am

I thought you had this piped up with the stove to tank one bottom, then top of tank one to bottom of tank two, then out of the top of tank two?

If I read this right you have both tied together at the bottom but feeding hot water to only one tank? and that is the one that is blowing off right?

 
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Post by plumberman » Sun. Oct. 30, 2016 7:05 am

add a 3 speed grundfos circ set on low speed to the picture. this should help you out with temp variations/blow offs.


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