Plumbing a skoolie

[Chopperpilot]

Ok planning my plumbing. I have a question. Has anyone ever ran one line from your cold pump to the end of the line say kitchen faucet and put T connections in for say bathroom sink and toilet before? If you did this have you had any issues? Planning to do this with hot water as well. I know the pressure maybe lower if the kitchen sick and bathroom sink are on at once but it will save running multiple lines through the bus.
Thanks in advance
Derek

[Chopperpilot]

Plan to use 3/4 pex so far.

[Oscar1]

Hello and welcome.
Sounds like you're on the right track, that's exactly how you do it. No need to run multiple line for either hot or cold. You can see many designs if you Google rv pluming images.
Good luck with your build and keep everyone posted.
Cheers

Oscar

[s2mikon]

Oscar1 said it best. I did it the same. I used 1/2" pex and it is plenty.

[A Crafty Beaver]

1/2" inch per throughout is most likely fine. Most people do not have high flow fixtures in a RV. 1/2" will get you about 7-14 gallons a minute of flow. A shower might do between 1.5 and 3. Your kitchen faucet might do 2.5 if its a standard residential. Lavatory might do about the same. So even with high flow fixtures, in what amounts to a single bathroom house 1/2" will run everything just fine.

If you want to over size it a bit, run 3/4" from your freshwater tank to your water heater cold inlet and run 1/2" everywhere else.

The picture Oscar posted is a perfect illustration on a great way to run the system. Only thing I would change is tying the water heater in as close to the pump as is practical(not that it will make a huge difference, just less 3/4 pipe and fittings needed)

Good luck with your build!

Source- am a residential plumber.

[Danjo]

As stated in another reply, 1/2” can deliver about 10 gallons per minute, if the supply is there. The bottleneck will probably be the pump which will probably be 2-3 gpm.

If you’re untethered you sure don’t want appliances that consume even 2 gpm at least not for long.

Short answer, 1/2” is plenty.

While we are on the subject, you may want to consider insulating those water lines.

[DAVEHOLMAN]

Originally Posted by A Crafty Beaver

1/2" inch per throughout is most likely fine. Most people do not have high flow fixtures in a RV. 1/2" will get you about 7-14 gallons a minute of flow. A shower might do between 1.5 and 3. Your kitchen faucet might do 2.5 if its a standard residential. Lavatory might do about the same. So even with high flow fixtures, in what amounts to a single bathroom house 1/2" will run everything just fine.

If you want to over size it a bit, run 3/4" from your freshwater tank to your water heater cold inlet and run 1/2" everywhere else.

The picture Oscar posted is a perfect illustration on a great way to run the system. Only thing I would change is tying the water heater in as close to the pump as is practical(not that it will make a huge difference, just less 3/4 pipe and fittings needed)

Good luck with your build!

Source- am a residential plumber.

Any particular reason to oversize the water heater inlet hose? I'm just getting ready to plumb my bus and planned 1/2 pex from start to finish. I just have a shower, toilet and sink.

[A Crafty Beaver]

Originally Posted by DAVEHOLMAN

Any particular reason to oversize the water heater inlet hose? I'm just getting ready to plumb my bus and planned 1/2 pex from start to finish. I just have a shower, toilet and sink.

Honestly, mostly a carryover from plumbing houses that don't move. It lets you use the full 1/2" line for just cold instead of having a bottleneck where the water is coming from the source to both the water heater and the faucet.

There are plenty of 2 bath houses that have 1/2" lines throughout and don't have any issues. In a skoolie, you probably won't ever be using that much water unless you are at a site where you are tied into the grid. Even then, hitting the max throughput of a 1/2" pex line is not really going to happen.

It also matters how many and what kind of fittings you're installing, for instance, the expansion joint pex has significantly better flow rates because the fittings are the same size as the pipe's inside diameter. The crimp joints fitting are a bit smaller and thus reduce your flow. Putting a bunch of fittings in a run of pipe will cause turbulence and extra friction also reducing flow rate(on either joining system).

Most of this doesn't really have any impact on a skoolie since the runs are fairly short and water usage is fairly low.

Feel free to DM me if you have more questions

TLDR

Go with 1/2", you'll be fine. If you want a bit of overkill on the project, plumb the section between the water supply and the water heater cold inlet with 3/4"

[o1marc]

Use 3/4" for the main run, and T off everything with 1/2".

[dave79mci]

Thats ok but if you ever have problems with any units connected you will have to shut down the whole thing, so I would at the very least put shutoffs at each unit incase something happens leaks etc. and you can't find or get it fixed right away you would still have use of the rest. Also what I did was put a 3/4" line as close to everything as I could and then that was attached and supplied water to a manifold with individual shutoffs for each unit or fixture then 1/2" off that to each fixture. Not that much more but able to isolate each.

[Drew Bru]

Originally Posted by DAVEHOLMAN

Any particular reason to oversize the water heater inlet hose? I'm just getting ready to plumb my bus and planned 1/2 pex from start to finish. I just have a shower, toilet and sink.

We used 1/2" Pex throughout and never had any problems with shower and sink. The flow was more than adequate for 2 adults and full time living.

[ChuckRatto]

Thats just what I did. I also just used 1/2 pex. Seems to work just fine. The smooth inner diameter of the pex allows for plenty of flow in an RV.

[rossvtaylor]

1/2 inch PEX isn't even 1/2 inch at the fittings most people use (Apollo or the like) and that works just fine in any RV. Wirsbo fittings are generally larger in inside diameter, but more expensive and harder to use (with a special expansion tool)...and it's overkill in an RV, from a flow perspective. Just don't use Sharkbite fittings, please, as someday the o-rings will shrink and leak. It may be a long time, but it will happen...

[Willie_McCoy]

Originally Posted by rossvtaylor

1/2 inch PEX isn't even 1/2 inch at the fittings most people use (Apollo or the like) and that works just fine in any RV. Wirsbo fittings are generally larger in inside diameter, but more expensive and harder to use (with a special expansion tool)...and it's overkill in an RV, from a flow perspective. Just don't use Sharkbite fittings, please, as someday the o-rings will shrink and leak. It may be a long time, but it will happen...

I agree with the sharkbite business, they are NOT to be concealed in any case and should be used for emergency repairs only.

As for the reduced inside diameter of insert style pex, while it is true, with the expected flow rates in conversions and RV's it is really a non issue. I would recommend poly (plastic, not brass) fittings and the stainless crimp rings as the best option for DIY plumbing.

[A Crafty Beaver]

Originally Posted by Willie_McCoy

I agree with the sharkbite business, they are NOT to be concealed in any case and should be used for emergency repairs only.

100% this

Originally Posted by Willie_McCoy

As for the reduced inside diameter of insert style pex, while it is true, with the expected flow rates in conversions and RV's it is really a non issue. I would recommend poly (plastic, not brass) fittings and the stainless crimp rings as the best option for DIY plumbing.

Any reason why you're recommending staying away from the brass fittings and copper crimp rings?

I know they had some issues with the brass for the fittings a while back, but I haven't seen that in about 10 years or so...

Not trying to call you out, just curious on your reasoning

[AresCha0s1]

Originally Posted by Chopperpilot

Plan to use 3/4 pex so far.

Use 1/2” as the 3/4” wont give you more pressure it’ll only give you more volume!

[Rucker]

Originally Posted by AresCha0s1

Use 1/2” as the 3/4” wont give you more pressure it’ll only give you more volume!

The pressure drop can be material, especially over long runs, and with many elbows or fittings.

Having said that, it doesn't seem likely you need 3/4". By way of example, a 1.5 GPM Ecotemp tankless heater is rated for 37,500 BTUs input. From this chart,

https://fire-boulder.com/wp-content/...PipeSizing.pdf.

You could theoretically run almost five of those units off a single 1/2" line.

Not sure PEX is the best choice though. That's another conversation.

[A Crafty Beaver]

Originally Posted by Rucker

Not sure PEX is the best choice though. That's another conversation.

Genuinely curious, what is your reasoning here?

[AresCha0s1]

Originally Posted by A Crafty Beaver

Genuinely curious, what is your reasoning here?

I too wanna know, I am a plumber and I won’t plumb with anything but PEX

[Danjo]

Originally Posted by Rucker

Not sure PEX is the best choice though. That's another conversation.

I was thinking exactly the same as you are, but then someone on the forum asked me ‘why not?’. So I used PEX and have to say that for the application it’s the best thing ever. I’d never put it in a house, but in an RV it makes sense.