Simple plumbing questions

[simpletradition]

Hi there,
So we are planning the plumbing out and I have a little question...
The guy helping us with the plumbing wants a 3/4 “ line coming from the city inlet valve into the water heater. We got a small residential 110 tank heater and the inlet to that is 3/4”..., but I can’t seem to find the right thing to buy online? Maybe I’m looking in the wrong places or I’m not understanding the numbers on the products being sold? But it looks like to me that most of these city water inlet valves are 3/4” coming in (a normal watt hose connection) and 1/2” fitting on the inside of the bus. Is there such a thing as a 3/4” and 3/4” city water inlet valve? Is there a reason why it should be 1/2 on the inside? Like maybe it helps with water pressure?
My guys plan is to run 3/4 to the water heater and then 1/2 to the rest of the bus. And solely for the reason that the water heater has 3/4 connections. I’m thinking we’re just going to have to put adaptors on those 3/4th... and just use all 1/2 thru out the bus. Any advice is appreciated. ;)

[Jolly Roger bus 223]

In the plumbing world it is normal and a good idea to match pipe size to equipment size.
I have never looked at the pre-made water inlet stuff but there should be one that is 3/4 to 3/4"? Would seem like a common item to me but I made my own?
The pipe size deals with gallons per minute at the supplied inlet pressure not decreasing the pipe size to create pressure because no matter the inlet pressure at a max a 1/2" pipe (don't quote me) is only going to supply 8-9 gpm at max inlet pressure where a 3/4" line will supply 10-11 gpm at max inlet pressure.
First you need to know the minimum GPM of the water heater you are supplying and the manufacturer usually decide's by providing that minimum.That is what really decides your line size. And the same goes for each fixture and 1/2" is normal for an individual fixture in a run but two or more fixtures or on the same run and there ever was a chance of more than one used at the same time then you need to size the line for the total amount of water expected of that run at any one time.
I have never decreased the line size going into a water heater.
But I have increased them to bigger pipe with no problems.
Could explain but no need to unless you just gotta know.
Hope this helps.

[simpletradition]

Thank you Jolly Roger. That explanation helps a lot. I will keep looking

[Jolly Roger bus 223]

Ok just googled a few and the 1/2" connection is all I could find also.
Not a problem. Your plumber will have to get the correct fitting to go from 1/2-3/4" .
That would drive aggravate me also.
But increasing the size of the pipe from the connection is very common not decreasing the size.
Long story short if you just have to know I can explain.
Maybe your plumber can? Increase the line to 3/4 as soon as you can from the 1/2" connection. In this case the line size has the volume of water to move and the smaller is able to feed it because there are no leaks and the volume and pressure are there.
Have upsized many outlets with expected results but have never downsized into the inlet.
After all of this I have to bring up things that those city water inlet things are missing?
Strainer
Pressure reducing valve
Check valve
Ask away

[T-Bolt]

You are overcomplicating the plumbing. Just make everything 1/2". You will never need the flow rate provided by a 3/4" line unless you are planning on a 2 bath skoolie.

[Drew Bru]

Originally Posted by simpletradition

I’m thinking we’re just going to have to put adaptors on those 3/4th... and just use all 1/2 thru out the bus. Any advice is appreciated. ;)

That's what I'd do....simplest way to go and no reason not to do it that way. 3/4x1/2 reducers are readily available.

[PNW_Steve]

Originally Posted by T-Bolt

You are overcomplicating the plumbing. Just make everything 1/2". You will never need the flow rate provided by a 3/4" line unless you are planning on a 2 bath skoolie.

Agreed.

1/2" for everything will work fine.