"But wait! There's more. Buy one and we'll send you a second Hot Water Lobster, absolutely free!" That's what you usually hear in one of those pitches for a totally useless gizmo. I'm surprised it wasn't included here.

How far is your kitchen from your water heater? Is your water heater in a basement, or on the same floor as the kitchen? Are your hot water pipes insulated? If your water heater is on the same floor as your kitchen and your hot water pipes aren't insulated, this thing's chances of working are pretty slim.

IMO, even if your kitchen faucet is directly above the water heater, and there are no other hot water taps in the house, the chances of this gizmo working are next to zero.

If you want a device that actually does work, take a look at the Grundfos Comfort System. It's designed for retrofitting an existing home with a hot water circulation system. It too, relies on the cold water pipe in place of a dedicated return line, but it moves hot water with a pump that's installed at the water heater. It will actually work.

There are also systems available from other manufacturers that also utilize pumps. Do a google search on "Residential Hot Water Circulation" and you can find several. Grundfos, however, is the leader in the field.

The Hot Water Lobster looks totally useless to me. Even the name is stupid.

Just my two cents.

Here is a link that might be useful: Grundfos Comfort System

You can buy the Watts version at Home Depot for $199. (made by Grundfos and uses their older style circ platform that works just fine)

I don't know if the 'lobster' would work or not, but I can think of two things straight away: 1) you are going to use more energy, not less, because your hw heater will actually have to heat more hot water, to keep the cold water warm and replace the heat loss in the hot pipes. Effective insulation would be better.
2) you are going to contaminate your cold water with hot water tank residue. This is a no-no and why you should have an expansion tank on the cold line of your hw heater if you have any sort of backflow prevention or check valve on your water supply - if you have a pressure regulator, water meter or any sort of backflow preventer, then you need an expansion tank.

Apart from actually consuming more energy (I suspect hw recirc systems do) I've also heard a lot of posters say it puts a much greater strain on the pipes using recirc pumps because of the added volume of water movement.

My ex wife's crusty old plumber grandfather told me you could balance your hot water flow and reduce hot/cold rushes by making your hot water into a 'loop' ie running a line back from the furthest hot tap, back to the hot outlet on the hw heater. I have been curious to try it in my house, don't know if it'd work (I may have misunderstood his instructions, but he was pretty smart about this stuff) or if it's legal...anybody know more about it?

pjb,

What your papa was describing was a old time gravity recirc loop.

Correction on the install though. The return pipe is tied into the farthest run or the run that you wish to achieve recirc on and it is not tied into the top, but extend out the drain and tie it into the bottom of the tank. Thus this only works with tanks, gas-fired is better and mainly performs only when burner or lower element is on.

I would like to hear more about this circ loop. Does the temp actually get far enough apart to flow? Does this increase demand on the heating justify the the conversion? Not counting the install cost. Does it help with the cold rush?

In order to tie into the bottom of the tank, would it have to connect to where the drain valve goes? I suppose that is doable, you would then put on a tee or similar to put the drain on, but would this be legal, and would it work? I suppose the water in the pipes would heat faster, but you might use more energy since there'd be more heat loss....

If it helped the pressure fluctuations, it would be a good thing. In my house, though, there's limited access to the plumbing since it's a finished basement, if I reno the kitchen and have to move some flooring (we have a squeaky section) it might give me enough access to consider it, I guess that's a place where Pex might be good, if you're blindly feeding a pipe through a tight spot (not to mention its insulating qualities, I guess for such a system, you'd want to insulate the pipes)

Thermosiphon loops work if the height differences vertically are not very large.

They are very wasteful of heat though.
The return line cannot be insulated since it is the loss of heat that drives the loop to circulate. A check valve is also needed to prevent back flow in the return loop when the faucets are opened.
The return line also must be as large as the supply side since the force generated by the cooled water is very low.

A pump system can use timers or sensors to only circulate water when needed, and can use a smaller insulated return line.
The power to run the pump still is much smaller than the pipe losses from having all the pipes always at tank temperature (or only slightly below).

Part of the trade off is the cost of wasted water vs. the cost of heating it, and the convenience of having 'instant' hot water.

I cant help wondering if we are not talking about two seperate techniques. Hooking into the top of the heater may indeed help with cold rushes. I would connect the pipe into a spot close to the furthest shower. It may even need a branch off of the second pipe at each shower to be effective at that shower.
Tapping into the bottom does indeed seem wasteful of heat.

All water heaters built after 1989 have internal "dip tubes". This is an internal pipe, which channels the cold water from the inlet connection (at the top of the tank) to the bottom of the tank for better efficiency. Therefore, the Hot Water Lobster Instant Hot Water Valve works fine-without changing any connections to your water heater.

After buying a Hot Water Lobster (did'nt work worth a s--t) and trying to deal with the company. I would,nt buy a Hot Water Lobster if they gave me 5 more for free. Worthless product.

Greg,

The Hot Water Lobster Instant Hot Water Valve is a GREAT product...mine has been working great for years!

If you read the system requirements before purchasing the Hot Water Lobster, you would have realized that it is designed to be used with hot water "tank" type water heater (where thermal convection is generated to circulate the water) and not intended to work with your "tankless" hot water heater.

JUNK! I bought this with the hopes of getting hot water at my master bath instead of waiting for a long time. Not the case. I installed it per the directions, waited a few hours and anxiously tried the hot faucet. Same old thing cold water for a good minute. Re-read instructions, retried 'flushing air pocket' out the Lobster. No change, cold water. I emailed Hot Water Lobster and they sent me the instructions which were included with the unit. I reviewed the instructions again and looked for reversing valves and manifolds in the water lines (which is lots of fun going through the crawl space in December). Turns out I didn't have any of those obstacles. Lastly, instructions say 'heat traps' in my water heater could be the cause. I reviewed the service manual for my water heater and low and behold, I have them! So that must be it, right? I emailed Hot Water Lobster, had them 'review my water heater specs' as they said they would do if you have this type of difficulty and they said they doubt the heat traps would cause it not to function, which I thought was strange since their instructions say it could, but to remove them anyway. I removed them, which took 1 trip to Lowes and about $10 for APEX connectors and water lines to replace what I had to cut apart to get them out. Turn the water back on, wait a few hours, same result, cold water out of the hot side. I emailed Hot Water Lobster again, no response. Now after reading other reviews I see this is their std procedure. I sent it back and did receive a refund less the $28 shipping (they charge $28 to ship via USPS priority mail that costs $11.35).

Buncha one post wonders hawking products smells awfully SPAMMY.