Tankless as a booster?

[MikeFromHC]

When my old water heater died I put the new one at the front of the house rather in the garage. (Previous owner used a *lot* of hot water in teh garage and it made sense.)
Now the front gets hot water fairly quickly but the back gets it slowly and it has cooled a lot.

Does using a small tankless heater to supply an initial flow of hot water and boost the rest when it gets there make sense in a situation like this?

[jadnashua]

That would probably work, but at a high cost. If you don't run out of hot water, but don't want to wait for it, why not put in a circulation system. You don't need to run it all the time - you could use a timer, or a momentary contact switch, or a proximity sensor to restrict the amount of time it is running. They range from say around $200-400 for parts, depending on the brand and type.

Keep in mind almost all tankless systems use a flow restrictor and if you have a big tub or a multi-head shower, the reduced flow might mean it takes longer to fill the tub or your pressure could be affected. Might not, but increased flow means bigger unit.

[MikeFromHC]

That would probably work, but at a high cost. If you don't run out of hot water, but don't want to wait for it...

Thanks. Waiting for it is not the problem. In winter the water that comes out at the back of the house is cool enough to shower in with no need to mix cold water if the water at the front of the house is at around 130 degrees at the faucet. (As I found out the hard way) This is a constant loss.
I have no idea how much underground pipe runs from front to back.
(A light goes on) But That might be a solution. Cut that underground section out and replace it with a straight run to the back.
Even uninsulated a pipe to air is going to do better than a pipe to wet earth.

[Redwood]

Mike, is the mixing valve at the tub/shower at the rear of the house a single handle type?

[jadnashua]

What Redwood is getting at is that all new (and they've been around for awhile) single handle anti-scald tub/shower valves have a limit stop. You might only need to adjust that to allow the handle to add more hot to the faucet output. Is the water temp at the vanity faucet hot? If so, that's probably your solution. That's one reason why I like thermostatically controlled valves, regardless of how cold the incoming water is, assuming it can, it will provide the same temp season-to-season. On a pressure balanced valve, you may need to change the limit stop from season-to-season if you want to maintain the safety margin.

[MikeFromHC]

Mike, is the mixing valve at the tub/shower at the rear of the house a single handle type?

No and before I moved the hot water heater from the garage the back of the house got hot and the front got warm.
There are no limiters on either. Also during the summer both get and got good hot water.

[jadnashua]

It might be cheaper to find a new way to run hot water to that end of the house.