The problem of the water heater at one end of the house and master bath at the other is a classic bad design.

A small point of use mini tank will provide you with immediate hot water for washing hands, etc. but won't provide enough water for a shower (they provide 4-6 gal) That would give you about 2-3 minutes of hot water in the shower... enough for the hot water from your main heater to get to the bathroom.

So, the answer is that you should plumb it in series with the existing water heater.

Are the hot water lines to the bathroom insulated?

Thanks Jake. I appreciate your response.
That's what I was hoping I could do. However, the spec on the Bosch model says "not intended for a hot water inlet" Do you know if it is possible to run cold water in and T off one outlet for the sink and the other into the existing hot line in the wall which would still be connected to house pressure?

I don't think the pipes are insulated. The plumbing is 99% plastic, except at the shower fixtures, as far as I can tell.

Mark,

The spec sheet for the heater shows it being used in series with a main water heater - which is the way you want to plumb it.

If you can't access the plumbing such that you can supply both the sink and the shower, just do the sink. That is where it will get irritating not having hot water in a hurry.

All of your hot water lines should be insulated. Do they run through a slab?

Here is a link that might be useful: Spec sheet showing connection to water heater

Thanks for the link. That's perfect. I must've read the no hot water connection somewhere or maybe I'm loosing it.

I do not have direct access to the line that goes to the shower, so I will start with the sinks, but the shower wastes the most water. Luckily, since its a new home, they are building more right now and I'm going to go check the plumbing layout to see how to tie into the shower.

No pipes running through slab. I'll see about insulation, but I doubt it. Is it typical to insulate the plastic pipes too?
Thanks again. - Mark

I think it's code that hot water lines are to be insulated... but you can find out. On a new house, I'd call the builder back. It's crazy to run a hot water line 50 feet with no insulation.

I'm curious as to why the recirc didn't work. My previous home was a ranch style with MB at one end and the water heater at the other. When we remodeled we had a recirc pump installed and we had hot water nearly instantly thru-out the house. I remember the pump was attached to a small tank which sat next to the water heater so I'm wondering if size/brand would make a difference in your situation.

I agree with nigelsgarden that the recirc should work. Did you run a new line back to the hot water heater and feed the recirculated water back into the cold water inlet fitting on the heater? There are easy to install recirc pumps which use the cold water feed to the bath room as the return pipe. The problem here is that with the recirc pump running you won't have any cold water, because the cold water pipe will get packed full of hot water.

Mark, if you saw anything discouraging feeding the mini hot tank with the hot water line it would have been to avoid the following situation":
1-You start showering, and the tank gives you nice hot water right away.
2-The nice hot water you use from the tank is replaced by the cold water in the 50 feet of pipe from the hot water heater to the bathroom.
3-As the limited supply of hot water in the mini hot tank starts to become exhausted, the shower will begin to cool down, because the cold purge water is filling the mini hot tank.
4-The shower probably won't go completely cold, because when the pipe purge is done, there will be hot water from the big hot water heater filling the mini hot tank, and the outlet temperature will rise again, until the temp at the shower equals the output form the main hot water heater.

If you like to sing in the shower, the cold phase might give your voice a nice operatic vibrato (caused by shivvering) and the arrival of the very hot water can help you with a couple of high notes till you get everything regulated.

Nigels,
I'm not sure why the recirc doesn't work, but it doesn't. I don't have a dedicated return. I installed the bypass valve that came with the pump to use the cold return under the sink in the master and the pump is at the tankless heater in the garage. There are no mini-tanks anywhere right now. The guys at Watts Premier said that the recircs don't work with tankless. Did you have a tankless water heater?
Stan,
I guess you're right. The mini-tank can't heat water fast enough to fill the void between the mini-tank being empty of hot water and the fresh cold water coming into it, right?
So what can be done?
Thanks.