Relative locations of sillcock, whole-house filter, PRV, expansion tank

[sindikeesan]

Is the following setup code and/or recommended?

82 psi.........................50 psi............................................... ............
meter=shutoff==filter==PRV===shutoff============== waterheater
.....................|.....................|...... ................|.............|...........|....... ...
.....................|.....................|...... ................|.............|...........|....... ...
..................sillcock ..........pressure ............exp.........cold......hot.....
.........................................gauge.... ...........tank........water...water....

(Plus addiitonal shutoff valves?)

filter - whole house carbon block filter, which reduces pressure as it ages
PRV - pressure reducing valve (required by code - Michigan, 2009 IRC)
exp. tank - expansion tank (required by code)

Is it code to put the sillcock and water filter before the PRV?

We want to measure incoming pressure at the sillcock rather than installing a second pressure gauge before the PRV, and to protect rubber parts in the expansion tank and keep sediment out of the PRV by filtering before them (as well as removing chlorine from inside water).

The inspector says PRV is required by code even if incoming pressure is 80 psi.

What is the standard setup and why?
We are Owner builders/architects.

[CarlH]

I'm not a plumber so I am not going to comment on the code aspects to this setup. It does look to be a rather unconventional setup. Is the shutoff between the meter and the filter easily accessible? Should a water leak emergency or maintenance be required with the sillcock, PRV or the filter, the water will need to be shutoff at the meter. Around here, that is not something the homeowner generally has access to because it requires a curb key to access the meter and co-located shutoff. I would expect that both the PRV and filter to be located after the in-house shutoff and the filter to be located after the PRV so that it is not subjected to the higher pressures. If you are worried about sediment, most if not all PRVs have a strainer built in. Also, why is measuring the incoming pressure important?

[sindikeesan]

"Why is measuring the incoming pressure important? "
Instructions for the PRV showed pressure gauges before and after - the one before may not be required.

Shutoffs before and after the meter, also after the filter(s)-PRV-gauge (whatever order they are in) before the expansion tank, and for each fixture. Any others recommended?

We could put a sediment filter before the PRV, and the carbon block filter after the sediment filter and either before or after the PRV.
How would higher pressure damage the carbon block filter? Supposedly they reduce the pressure when they have been used for a while, so putting them after the PRV might lower the pressure too much.

Meter and shutoffs will be in the crawlspace near the access door (under the stairs). We plan to use a 29" high lowboy water heater with a drip pan draining to a trap in the adjacent cellar and a water leak sensor in the pan. This minimizes length of hot water pipes. Also a relay and timers to turn the water heater on and off (eliminate standby losses and take advantage of time of day electric rates which are higher 11 am to 7 pm). 10-15 min provides enough hot water for a shower (cost about 7 cents). (http://waterheatertimer.org). The expansion tank should prevent the T/P valve from leaking like it did here when water temp goes from 60 to 120, as should lowering incoming pressure from over 80 to 50 psi, since the leaks occur above 150 psi (due to hot water expanding) and the pressure won't be as high to start with. Comments on all this welcome.

The inspector discouraged us from using a tankless heater with our 100A service - 2 60A breakers needed instead of 1 30A one.

[hj]

At 80 psi I would just crank the PRV to its maximum setting as long as the incoming pressure is only 80 psi. You would be an unusual user if 50 psi gave you a satisfactory shower. I always set my customers at 75-80 psi. At that pressure, it makes no difference what the order of the devices is, but the expansion tank should be on the cold water supply to the water heater, between the tank and the shutoff valve. A tankless heater using 2 60 amp breakers would be marginal, most adequate ones use 3 60 amps or 2 100-120 amp breakers.

[sindikeesan]

We could get over 2 gpm water with 40F temperature rise using a tankless heater that takes 1 60A breaker, or 1 gpm with 1 30A breaker, which is more than adequate for the way I shower (90F, 1/2 gpm) but the inspector wanted us to put in something that would let several people use water at once, wastefully. A larger tankless model would not even turn on unless you ran at least .6 gpm, so that we could not use it at a kitchen sink to just rinse things. A smaller one would take too long to fill the tub. So we are going with a tank and a timer (which means a 30 min wait before filling the tub but at least you don't have to stand there watching).

Would 50 psi be okay for a low gpm shower?