Sidearm Plumbing Help Needed
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Take a look at this tread. You will need to rethink how you are plumbing this.
https://www.hearth.com/econtent/index.php/forums/viewthread/8168/
https://www.hearth.com/econtent/index.php/forums/viewthread/8168/
Thanks Don. I had read that thread before posting.
I am still at a loss of how to plumb the two lines, one from the top of the sidearm, the other from the bottom. The exchanger is hot. Hot water is being pushed out into the pex line, but runs cold after about 5 feet. The bottom line out of the drain valve in the tank is hot for a few feet.
My guess is that the hot water cannot overcome the water pressure and therefore does not siphon.
Since almost everyone on the boiler room has a sidearm, I thought someone might offer a suggestion how to plumb it. With only two lines, how complex can it be? Yet I can't get it to work.
I am still at a loss of how to plumb the two lines, one from the top of the sidearm, the other from the bottom. The exchanger is hot. Hot water is being pushed out into the pex line, but runs cold after about 5 feet. The bottom line out of the drain valve in the tank is hot for a few feet.
My guess is that the hot water cannot overcome the water pressure and therefore does not siphon.
Since almost everyone on the boiler room has a sidearm, I thought someone might offer a suggestion how to plumb it. With only two lines, how complex can it be? Yet I can't get it to work.
I am not an expert by far but have built a couple of sidearms.I think you should have the pipe leaving the top of the sidearm plumbed to the hot side or to a T where the blow-off is. the cold side has a drop tube stopping short of the bottom of tank causing there to be little if no temp difference between one end or the other of siphon loop.
I think the pex run may be to long. Horizontal runs within the loop detract from the flow of water...Vertical runs make the delta T flow the water. A short loop plumbed close to the tank in a vertical fashion will create the delta T to get the waterflowing. I also agree to use the side blow off fitting as return port into you hot water storage tank.
I agree with both previous posts. Look at your diagram and that of Eric's in the link I suggested. They are not the same. Your sidearm should not flow back into the mixing valve, It should go into the side of the tank where the pressure relief is located. Just tee that connection and put the pressure relief back in. Look for examples on this site of how to connect the mixing valve. Redraw your diagram correctly and repost for comments before making changes just to be sure you have it correct..
There are many things wrong with the piping in the picture, but the question is why does it not work. It does not work because there is no way for it to thermsyphon. The reason no thermosyphon is occuring is because you have piped your side arm into the cold supply of the water heater. The cold supply has a dip tube. That tube runs to the bottom of the heater and that is how cold water is suppled to the tank. The themosyphon principle relys on natural convection to work, you killed that, basicly you created a heat trap.
Where is your tempering (mixing) valve?
Where is your tempering (mixing) valve?
The mixing valve is still in the box but is part of the plan.
I'll plumb into the PRV opening with a cross so that the line out of the top of the sidearm comes into the top of the cross. The PRV will go on the right arm. The Left arm of the cross will go into the tank where the PRV was previously. The lower arm of the cross will be a ball valve for extracting water for odd-ball uses. The drain valve in the tank will be plumbed to the bottom outlet of the sidearm.
Ironically, that is what I had originally planned to do, but I was afraid to disrupt the PRV thinking that I might break it off, (in the attempt to extract it, leading to complications and expenses. Regrettably, I opted for an incorrect solution.
Mhearts thinks the pex is too long. That might be right. In the barn I had thermo-siphoning for almost 40 feet through 1/2" pex; so I'd like to at least try the above re-plumbing suggestions in hopes that the thermo-siphoning will work.
If I have to move the sidearm to the tank for better thermo-siphoning, it will have to wait for spring/summer. I'd rather move it then add a pump to the circuit but I think that would work also.
I'll plumb into the PRV opening with a cross so that the line out of the top of the sidearm comes into the top of the cross. The PRV will go on the right arm. The Left arm of the cross will go into the tank where the PRV was previously. The lower arm of the cross will be a ball valve for extracting water for odd-ball uses. The drain valve in the tank will be plumbed to the bottom outlet of the sidearm.
Ironically, that is what I had originally planned to do, but I was afraid to disrupt the PRV thinking that I might break it off, (in the attempt to extract it, leading to complications and expenses. Regrettably, I opted for an incorrect solution.
Mhearts thinks the pex is too long. That might be right. In the barn I had thermo-siphoning for almost 40 feet through 1/2" pex; so I'd like to at least try the above re-plumbing suggestions in hopes that the thermo-siphoning will work.
If I have to move the sidearm to the tank for better thermo-siphoning, it will have to wait for spring/summer. I'd rather move it then add a pump to the circuit but I think that would work also.
Eric Johnson
Mod Emeritus
Hi, Tim.
Because you're relying on gravity, things like the distance of the sidearm from the tank itself might cause a problem. I also notice that you're piping into the cold water feed line. That's not how it's typically done, and it might also be part of the problem.
All I know is what works in my case, and that would be to hang the sidearm on the tank itself and connect the top to the PRV outlet, instead of the cold water supply, as per my diagram. I've had at least three sidearms hooked up this way, and they all worked well.
If it's impractical to reposition the sidearm, then at least make sure the lines are well insulated. You might also consider putting a circulator on there. I did that once and got (I think) about 7 or 8 years out of a simple cast-iron Taco 007. That would solve any thermosiphon problems, and allow you to put a check valve somewhere, which is something that will typically stall out a regular gravity feed arrangement.
In any event, I'd re-pipe the top of the run into the PRV outlet. I think that's probably your biggest problem.
Oh, one more thing: If you have mineral deposits in the bottom of your hot water heater, it will stop the thermosiphon flow. If you have hard water like I do, you need to drain about 5 gallons off the bottom of the tank periodically (like once a month) to keep it clear. If yours is jammed up now, you need to flush it out really good.
The last thing you want to hear, my friend, are those dreaded words: "Honey, there's no hot water."
Because you're relying on gravity, things like the distance of the sidearm from the tank itself might cause a problem. I also notice that you're piping into the cold water feed line. That's not how it's typically done, and it might also be part of the problem.
All I know is what works in my case, and that would be to hang the sidearm on the tank itself and connect the top to the PRV outlet, instead of the cold water supply, as per my diagram. I've had at least three sidearms hooked up this way, and they all worked well.
If it's impractical to reposition the sidearm, then at least make sure the lines are well insulated. You might also consider putting a circulator on there. I did that once and got (I think) about 7 or 8 years out of a simple cast-iron Taco 007. That would solve any thermosiphon problems, and allow you to put a check valve somewhere, which is something that will typically stall out a regular gravity feed arrangement.
In any event, I'd re-pipe the top of the run into the PRV outlet. I think that's probably your biggest problem.
Oh, one more thing: If you have mineral deposits in the bottom of your hot water heater, it will stop the thermosiphon flow. If you have hard water like I do, you need to drain about 5 gallons off the bottom of the tank periodically (like once a month) to keep it clear. If yours is jammed up now, you need to flush it out really good.
The last thing you want to hear, my friend, are those dreaded words: "Honey, there's no hot water."
Thanks Eric. The PRV input was going to be the next step. Insulating the line is a good idea. I thought circs would wear out fast but if I could get say 5 years out of a circ in this application; I'd think it worth it.
A circ might give a faster recharge rate on the DHW too. I'll plumb without the circ first and see if that works.
Thanks to everyone for their help.
A circ might give a faster recharge rate on the DHW too. I'll plumb without the circ first and see if that works.
Thanks to everyone for their help.
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