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Old 07-06-2012, 09:40 AM   #1
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Water Heater - pipe coming from drain/flush valve?


On my old water heater there was a standard hot water line running out at the top. HOWEVER, the previous installer also had a hot water line running from the bottom using an additional attachment placed before the flush/drain valve. He had a line running from that.

What I ended up doing was cutting that line and placing a T at the top hot water out. That works fine, but now I'm noticing that it takes significantly longer for the hot water to reach our shower. I'm pretty sure the line that was connected to the base goes to our master bath.

My initial thinking is that there would be higher pressure at the base of the heater, thus forcing the cold water out faster by having a hot water line attached there. The negative would be that sediment would be pushed up and into the line?

Does anyone have any thoughts? Why else would someone attach a line to the drain?

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Old 07-06-2012, 09:49 AM   #2
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Water Heater - pipe coming from drain/flush valve?


The pressure inside a sealed tank would be equal in all directions.
Personaly I would never have plumbed anything to that drain line like that. And your right it would dump all the heavy sedimant right into the supply lines which would end up plugging up the aeriators on the faucets.
Are you sure it did not go to a cirulator pump?

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Old 07-06-2012, 10:05 AM   #3
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Water Heater - pipe coming from drain/flush valve?


Sounds like they plumbed for a recirc line. Look for pump nearby.

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Old 07-06-2012, 12:54 PM   #4
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Water Heater - pipe coming from drain/flush valve?


I'll have to do some searching to see if there is a pump. The ceiling in the basement is finished. Perhaps it will be in the crawl space under the master bath.

Will it hurt the pump the way that I have it setup right now (if there is a pump)?

Also, when I was setting up the water heater if I turned on the cold water, then turned on the shower, cold water would start gushing out of the "hot water" output pipe. I'm really confused by that. Would that negatively impact the hot water output?
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Old 07-06-2012, 09:01 PM   #5
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Water Heater - pipe coming from drain/flush valve?


A recirculation loop would draw water out of the normal water heater hot outlet, up the normal line to the bathroom some distance away, then (just before the faucet) back down an additional line to re-enter the water heater, here via the drain valve. So sediment would not be going up into the plumbing system.

Some recirculation loops will work with no pump, the method is called gravity feed. How well it works depends on the exact positioning and routing of the outgoing and return pipes. The arrangement of the pipes is much the same as with a forced recirculation loop (with pump). The gravity loop should return the water into the tank as low as possible on the tank and this may be why the drain valve was used. If you took the pipe that was connected to the drain valve and hooked it up to the outlet pipe at the top of the water heater using a tee, then gravity recirculation will stop and a pump would be needed. Also it won't accomplish anything because the same water will now be going around and around in the loop and cooling off without new water from inside the tank joining the mix.

A gravity hot water recirculating loop works best if the outgoing pipe has only horizontals and rises (no dips or sags) and the return pipe has only horizontals and drops (no rises or up-and-overs).
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Last edited by AllanJ; 07-06-2012 at 09:15 PM.
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Old 07-07-2012, 03:25 AM   #6
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Water Heater - pipe coming from drain/flush valve?


Quote:
Originally Posted by AllanJ View Post
A recirculation loop would draw water out of the normal water heater hot outlet, up the normal line to the bathroom some distance away, then (just before the faucet) back down an additional line to re-enter the water heater, here via the drain valve. So sediment would not be going up into the plumbing system.

Some recirculation loops will work with no pump, the method is called gravity feed. How well it works depends on the exact positioning and routing of the outgoing and return pipes. The arrangement of the pipes is much the same as with a forced recirculation loop (with pump). The gravity loop should return the water into the tank as low as possible on the tank and this may be why the drain valve was used. If you took the pipe that was connected to the drain valve and hooked it up to the outlet pipe at the top of the water heater using a tee, then gravity recirculation will stop and a pump would be needed. Also it won't accomplish anything because the same water will now be going around and around in the loop and cooling off without new water from inside the tank joining the mix.

A gravity hot water recirculating loop works best if the outgoing pipe has only horizontals and rises (no dips or sags) and the return pipe has only horizontals and drops (no rises or up-and-overs).
hope i don't say this wrong, i'm trying to understand this gravity theory.Ok water has let say 40 to 60 psi hot water out top of w/h and for argument goes up 1" rise to first fixture then 1" up to next fixture and so on, lasts fixture starts back to w/h with perfect fall down to bottom inlet/drain your saying that would work as good as a circ pump.I'm thinking without the circ pump the return would only be some what useful only when using h/w with a pump it's circulating when not using so when you do open a valve instant h/w i know almost instant.Won't pressure push water from tank down 10' back then up to w/h.Again i'm not saying your wrong just never heard of it used in this application only with a boiler when heating using radiators-steam.Still willing to learn.
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Old 07-08-2012, 05:55 AM   #7
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Water Heater - pipe coming from drain/flush valve?


Gravity flow of water in a loop happens because hotter water is less dense than cooler water and tends to rise. The pressure in the system does not matter. Gravity flow does not happen fast and is significant only when no water is being used.

For both pump fed and gravity feed, the "recirculating" pipe must have a check valve so that when water is used, all comes from the regular hot water line from the top of the water tank and no possibly cooler water comes out of the bottom of the tank and up the recirculating line. In an actual gravity loop, a check valve must be positioned so it "drops open" in the water filled pipe if there is no water flow and is not stiff.

Still, you should check your system to see if there is a pump.

By the way, a steam heating system requires some steam pressure generated down at the furnace to push the steam up the pipes to the radiators. At first the steam condenses up in the radiator (which is what heats up the radiator) preventing a pressure equilibrium from happening up there so more steam will keep coming up. When/if the radiator gets hot enough the steam stops condensing and the radiator fills with steam and the flow up from the furnace stops. (Usually the room warms up enough and the thermostat stops the furnace before steam stops condensing inside the radiators.)
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Last edited by AllanJ; 07-08-2012 at 06:07 AM.
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Old 07-09-2012, 10:28 AM   #8
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Water Heater - pipe coming from drain/flush valve?


Allanj,

Thanks for your insight. I find that information extremely helpful. Based on what you have said, I'm pretty sure it was using a gravity feed. There is a valve that was hooked up to the gravity feed line that was going down to the drain. I'm going to close that off for now since it seems I just end up forcing twice as much cold water through the "T" (since it just sits there).

Regarding the "check valve", should I be able to get one from Menards? Is there something specific I should ask for? I'll probably reconnect the gravity feed if closing off the line doesn't improve the time for hot water to reach the faucet.

Thanks again!
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Old 07-09-2012, 05:46 PM   #9
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Water Heater - pipe coming from drain/flush valve?


I wanted to confirm that shutting off the valve for the line that was the gravity feed cut the time for hot water by a significant amount. The water gets warm very quickly, and hot in less than half the time as when I had the valve open.
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Old 07-09-2012, 06:00 PM   #10
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Water Heater - pipe coming from drain/flush valve?


Can you possibly post a picture of your piping? I'm curious and also a little confused by your description.
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Old 07-09-2012, 10:06 PM   #11
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Water Heater - pipe coming from drain/flush valve?


The valve I am referring to is the one that goes into the "T". I turned that off (this line originally ran to the drain on the old w/h), thinking that I was just pushing water in a circle. I'm not 100%, but I think it helped. I did another test and the water didn't heat up quite as quickly.

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Old 07-09-2012, 10:08 PM   #12
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Water Heater - pipe coming from drain/flush valve?


The term is thermal siphon will only work if the servicing plumbing is above the water heater very inefficient. He may also have an A/C recovery system.????? The things people go through to avoid paying for professional work. Saving a few bucks now usually ends up costing more down the line in one shape or form.

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