Sizing new water system

[Jose4291]

I currently have no running water but plan to install a 600 gallon in ground water tank next summer. My fresh water pump has 1/2" fittings and my tankless hot water heater has 3/4" fittings, the runs will be very short from supply to water heater, kitchen sink and shower, no greater than 20', my home is 600 sq. ft. I will have a very small radiant floor heating loop to protect the water tank from freezing during the winter. Do I size my water system pex pipe by the water pump connections (1/2 inch) or my V65IP Rinnai hot water heater (3/4 inch)? In other words, do I use 1/2" pex for connections and bush up for the water heater or use 3/4" pex for connections and reduce at the water pump?

 

[Mliu]

A water supply pump with only 1/2" fittings? That pump is going to be severely underpowered, even for just a kitchen sink. I doubt you could run a shower. I think you may be using a water recirculation pump.

You should post the specs on your pump.

Btw, what is the source of water for filling your 600g tank?

 

[Sponsor]

 

[WorthFlorida]

Check the V65IP Rinnai if it needs water pressure to operate. Tankless units will not fire assuming without water pressure there is no water in the burner section. Are you installing a pressure tank or already have one? For your little home one of these small compact pump and pressure tank units would be sufficient. https://www.homedepot.com/p/Superio...Jet-Tank-System-With-24L-Tank-94525/302330531

 

[Reach4]

3/4 inch pex. That can still be used after you get the new cistern tank and the new pressure pump.

 

[Jose4291]

The pump I have purchased is the Aquatec 5513-1Eo1-B606, 6 gpm@60 psi, 115 vac Superflow delivery/demand pump.
with 1/2" fpt fittings. The tankless water heater is a Rinnai V65ip, 6.5 gpm, 150,000 btu, with minimum water pressure of 20 psi and recommended water pressure of 30-80 psi. Pump will be located under the hot water heater, holding tank will be located approximately 20 feet away from pump, shower connections will be less than 6 feet away and kitchen sink less than 10 feet away. My next door neighbor has a good deep well 35 feet lower and 75 feet in distance from my storage tank, I'll have to purchase a gasoline engine transfer pump, most likely a Honda WX10 or WX15 and probably will filter the water before the reservoir with coconut activated charcoal. I may have to also get a pressure tank because of the small heating loop planned for the floor of the water tank enclosure and using a temperature controlled circulation pump, probably a Grundfos Alpha 1.