Plumbing pex where?

Tiffcat0502 · 06-07-2022, 07:30 PM

So I'm doing the plumbing now and our shower is opposite to our kitchen sink and to go around the back bed to get across to the shower is pretty far and a pain. I was just going to go over the top (roof) which is going to be insulated, it's not very far that way but would have to go to the middle of the bus before coming back down. Would there be enough pressure to run it over the roof?

turf · 06-07-2022, 08:14 PM

yes, most pumps should be fine.

as far as water pressure goes, the height difference between the pump and the outlet of the shower and the length of the pipe are the only factors that affect your pressure.

the shorter run of pipe will have the least friction loss.

with pex, you'll lose about 5 psi per 100' of pipe.
with the elevation change of about 6' you'll lose about 2.5 psi.

if your pump is 40 psi, minus the friction loss for ~ 20' of pipe (1psi) and minus the elevation change (2.5psi), your shower pressure will be about....36 psi.

read the info on your pump, this has to do with feet of head. if your pump is rated for more than 6' of head, you'll be ok.

Tiffcat0502 · 06-07-2022, 08:45 PM

Thank you I'll take a look at the pump and check what it says on it

turf · 06-07-2022, 08:53 PM

it'll work.

psi and feet of head are about the same thing.

40psi is about 100 feet of head.

if it can make 4psi, its going to work. at 40 psi it work well.

more important is the gpm's. 3 gpm's is the minimum, imo. 5gpm is ideal

Tiffcat0502 · 06-07-2022, 09:34 PM

If we do end up having to get a bigger pump as well we will I know its over 3 gpms.
Is feet of head high over the pump it can go?

Rucker · 06-08-2022, 09:03 AM

Quote:

Originally Posted by Tiffcat0502

So I'm doing the plumbing now and our shower is opposite to our kitchen sink and to go around the back bed to get across to the shower is pretty far and a pain. I was just going to go over the top (roof) which is going to be insulated, it's not very far that way but would have to go to the middle of the bus before coming back down. Would there be enough pressure to run it over the roof?

Curious where your freshwater tank is and what kind of water heating you plan to use.

Tiffcat0502 · 06-08-2022, 09:23 AM

Quote:

Originally Posted by Rucker

Curious where your freshwater tank is and what kind of water heating you plan to use.

Unfortunately we don't have an ideal setup at all, our freshwater tank is under the bus behind the wheel well on the drivers side and the Grey is under the bus on the driver's side as well in front of the wheel well. We wanted to do the tanks opposite of each other in front of the wheel well but we can't fit anything on the passenger side with the gas tank there and the exhaust. And we are using a propane instant water heater.

Rucker · 06-08-2022, 09:45 AM

Quote:

Originally Posted by Tiffcat0502

Unfortunately we don't have an ideal setup at all, our freshwater tank is under the bus behind the wheel well on the drivers side and the Grey is under the bus on the driver's side as well in front of the wheel well. We wanted to do the tanks opposite of each other in front of the wheel well but we can't fit anything on the passenger side with the gas tank there and the exhaust. And we are using a propane instant water heater.

I'm seeing more challenges with how you will run the drain lines. Do you have any installed yet?

Tiffcat0502 · 06-08-2022, 10:10 AM

All I keep seeing is challenges :"( the drain lines are going to be under the bus. But we do not have any installed yet but the Grey is directly under the shower so at least there's that. The kitchen sink will be the issue

Chrise · 06-09-2022, 11:59 AM

I have a similar issue. but it's about making the hot water run to the shower. I want to keep the run short to reduce the heat loss along the way. Same as you, the kitchen (where the HWH is located) is across from shower. So I am considering routing a 1/2" groove in the plywood sub floor to run the Pex in. the subfloor is 3/4" and has an inch of foam under it so it is sorta insulated. I figure I will use a leveling compound to cover the pipe before installing the floor covering.

This route shortens the run by at least 8' from the other option which is to run the pipe under the bed.

Plumbing is a sleeping dog.

Chris

Tiffcat0502 · 06-09-2022, 12:20 PM

Ouf that's going to be a pain to do but that sounds like enough insulation at least. Ideally running through the floor would be good cutting that groove will be "fun" but alot shorter for us as well it would be like 2 feet to cross but I'm not sure we could open the floor back up, I'll look into that as well thanks. Plumping is a sleeping dog and leaks are not a good thing it's super important

Ross · 06-15-2022, 07:36 PM

Regards hot water heat loss in piping : I ran a recirc system that tees off the hot feed at the mixing valve, through a very small 12vdc pump rated for hot water and back to the cold inlet on the water heater, with check valves where needed. Marine type switch in shower enclosure controls recirc pump. Really saves water. None is wasted waiting for hot water to reach shower (that's just water you're taking from the fresh tank and putting it into the grey tank for nothing). Turn on recirc switch, wait about 20-30 seconds, and hot water is right at the mixing valve without actually consuming any. During shower, the flow is paused at the shower head (has a button shutoff) for soaping up, and running the recirc at that time keeps hot water at the ready when the pause button is released for rinsing. All without needing to adjust the temperature at the mixer. We have a standard Suburban 6 gallon water heater, (cheap, pilot ignition) both of us can shower and not run out of hot water. We can boondock 2 weeks on our 80 gallons of water, each of us showering every other day, and still have some left. Just an idea.

Chrise · 06-15-2022, 08:03 PM

That circulation idea sounds most excellent. I have already installed an "instant" on-demand h2o heater. Do you suppose that plan would work with an on-demand unit?

Rucker · 06-15-2022, 08:08 PM

Quote:

Originally Posted by Ross

Regards hot water heat loss in piping : I ran a recirc system that tees off the hot feed at the mixing valve, through a very small 12vdc pump rated for hot water and back to the cold inlet on the water heater, with check valves where needed. Marine type switch in shower enclosure controls recirc pump. Really saves water. None is wasted waiting for hot water to reach shower (that's just water you're taking from the fresh tank and putting it into the grey tank for nothing). Turn on recirc switch, wait about 20-30 seconds, and hot water is right at the mixing valve without actually consuming any. During shower, the flow is paused at the shower head (has a button shutoff) for soaping up, and running the recirc at that time keeps hot water at the ready when the pause button is released for rinsing. All without needing to adjust the temperature at the mixer. We have a standard Suburban 6 gallon water heater, (cheap, pilot ignition) both of us can shower and not run out of hot water. We can boondock 2 weeks on our 80 gallons of water, each of us showering every other day, and still have some left. Just an idea.

Great design! Makes me want to take out my instant water heater and put in a regular one.

As I've posted elsewhere, instant water heaters monitor the temperature of the water coming into them and very quickly shut off when the hot water is recirculated as Ross describes. I wish I knew this before I built my system, struggled for days to troubleshoot it, then basically ripped out the recirculating portion of the design.

Ross · 06-15-2022, 08:32 PM

Chrise, Rucker beat me to it. There needs to be SOME reservoir of hot water for it to work.
So, you're in Bow? I'm just a bit south of Bellingham, right off I-5 exit 246. Happy to show you what I've built, and look at yours. Give me a call or text if you like. 360-319-0050

sportyrick · 06-15-2022, 10:24 PM

I ran 5/8 pex and if I had it to do all over again it would be 1/2 or 3/8. Your trying to conserve water anyway, you don't expect a heavy stream either so smaller is better in my eyes. You can get quite a bit of water through a 3/8 line with good pressure.

Ross · 06-15-2022, 11:21 PM

Sportyrick is right. 1/2 inch pex is plenty big enough. Water will get to your fixtures faster through smaller pipe. For any given flow rate, a liquid will travel a distance faster in smaller diameter pipe.

turf · 06-16-2022, 12:11 PM

x2 on the 1/2" pex

using pipe smaller makes friction losses great enough to affect the performance of your water pump.
using pipe larger is more expensive and not needed in an RV.

sportyrick · 06-16-2022, 02:34 PM

I also put all my water stuff on one side. All you people that split your water to both sides of your bus are asking for miracles on pluming and drain routes plus it makes it much harder to insulate properly. Black tank is rite below the toilet and I can see directly into it. Gray is directly below the shower, kitchen sink runs over to it down the shower wall, fresh water is directly below the hot water heater which is under the kitchen counter and stove adjoining the shower wall. It's all together in 5' on the drivers side in front of rear wheels which is where the dump is of course.

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