04:21PM | 11/09/04
Member Since: 11/08/04
2 lifetime posts
I have a gravity fed hot water recirculation system in my house that has given us great, fast hot water. 75G Bradford-white hot water heater; 2 storey house with hw heater in basement.

However, we've discovered that hot showers can turn lukewarm pretty fast with the return line open -- especially for the person who is second in line for the shower.

With the return valve closed, we don't have this problem -- hot water is plentiful. But we have the "3 minutes to hot water" problem, which is why a return appealled to us in the first place.

It is weird, the 1st hour rating on this 75G water heater is great, so it is hard to imagine that we could be out of hot water in 10 minutes of showering (primary shower head is not a 2.5 gpm head, but shhhhh, don't tell anyone...).

I wonder if the balancing valve in the shower is somehow mixing hot water with cold and sending the mixture down to the hot water heater?

So diagnosing help would be great.

But, I'm also wondering if I can kill this problem at the hot water heater, since I know that with the valve off there I enjoy long hot showers. Could I install a valve on the return line that would shut off the return when the water fell BELOW a certain temperature, yet stayed open when the water was pretty hot? All the thermostatic valves I've seen work the other way around.

Thanks for any help in diagnosing and fixing this problem!



05:48PM | 11/09/04
Sounds like your system is not circulating. That when you shut the system off you have plenty of hot water from the tank. But with the system on you are not pulling all hot. I doubt it is the shower valve. It is often hard to get a gravity system to work.

I presume your system must be designed correctly and that it has worked for several years. Was the heater changed recently or the temperature lowered on the heater? What event may have occured around when you started having the shortage of hot water?

I am not aware of a valve that shuts the flow down but there may be one. I have not worked on a gravity system in twenty years so my knowledge is not the best.


06:07PM | 11/09/04
Member Since: 11/08/04
2 lifetime posts
Lonny, thanks for your reply. House is new and builder was pretty good. Codes in my town are unbelievably strict, (copper required, cast iron no-hub required, galvanized sump required, etc.) So hoping the system was well-designed, but no way for this novice to know.

So when you say the system is not pulling all hot, what do you mean?

Would a recirculation pump fix this, provided it was designed properly? Does that typically mean you have to add other items, too?



08:42PM | 11/09/04
If your new house is still under warranty you should call the builder. Has this system ever worked? Yes a pump would cure gravity recirculation problems but it's about $200. for the pump. and maybe the same each for the plumber and electrician. You shouldn't have to do that if it's a simplier matter of getting your system to work correctly.

Oh, do you have a check valve on the circulating line? I think you should post your question on There are two threads on recirculating lines going on now and there are plumbers there more experienced than I am on the circulating lines. Perhaps one of them have gravity knowledge. You can say LonnythePlumber sent you.
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