Fresh hot and cold water circuits in a bus

[Paladin]

Has anyone ever tackled writing up a primer on various ways of building the water distribution both hot and cold in our buses? Anything in BCM?

I find myself again searching for any of the things I've run across over the years. Yes, I know Craig laid his out quite well and I've seen a couple others here and there but I was wondering if anyone has ever actually made a tech article on it? It would be cool to see tips, tricks and basics all laid out. 

[Jeremy]

I'd be interested to see this too. I think there is no such thing as the 'best' way of doing it though, as the system you choose depends upon how you are heating the water, how it will be pumped or pressurised, and so on. Your hot & cold fresh water circuits may also relate to the heating circuits and engine water circuit as well.

If various illustrations showing the different circuits people have used in their buses could be assembled in one place then it would certainly be a wonderful asset to new converters

Jeremy

[bevans6]

I'm not going to write an article on bus plumbing, but I think the choices are fairly clear - home runs to usage points, or daisy chain.  the traditional way is daisy-chain - run one supply line along the bus and tap off from it to supply faucets, etc.  That's how mine is done - cold runs along, head, shower, bathroom sink, kitchen are tapped off and the cold run terminates at the hot water heater.  Hot water just runs back along, terminates at the shower.  City water is tapped into the middle, as handy and appropriate.  My bus layout puts all points of water usage in a roughly 12' lineup along one side of the bus, to facilitate plumbing issues and make a daisy-chain layout work best.  With only two people on board, it is trivial to only have one point using water at a given time, making distribution efficiency rather moot.

Probably the better way is to home-run lines to each usage point from manifolds located at the water source.  More even distribution of flow and pressure, easy to manage, easy to  isolate and fix.  Central location of hot water near the cold source makes it even easier, and if you use pressure accumulators they can be more effective located at the manifold.  You do use more tubing, but PEX lends itself to this - easy to bundle and route, easy to terminate.  Many high end houses are going this route, since it really is better, and the manifolds are available off the shelf now where a few years ago you had to  build one yourself.

Put shut-off valves on the whole system and at each usage point.  That's about all I have...  It's worked fine in my bus, anyway.

Brian

[Bill B /bus]

I second the home run all water lines from a manifold or valve block made from available fittings. If you have a leak or have to fix a fixture then shut off valves are worth the money. PEX tubing is the way to  go. And it goes in color  so blue for cold and red for hot.

Don't forget when you are designing your system to include pressure regulator for incoming water, valve path to dump air from supply hose, drain for system and tank and finally a suction side line for pump where you can tank on disinfectant to clean system or antifreeze.

Draw out your system and check for ease of use. That is probably the critical step. Yes, I have a shutoff valve but its a stinker to operate! Think and try first before building.

Bill

[bevans6]

I forgot something really important in bus plumbing - making sure you have a way to drain it!  Drain it all for winterization means having a low point valve and gravity feed or blowing air to clear the lines.  Don't forget having to winterize the hot water system.  On my bus I have cleverly designed in a loop that cannot be drained, I have to disassemble to get the water out and condensation still accumulates.  So this winter's pre-winter task is to rebuilt that section with a drain!

Brian

[boogiethecat]

I like the daisy chain method for hot water.  Reason?  From each outlet or spigot  you can put a little valve that routes the hot water back to the fresh water storage tank.  When you need hot, open the valve for a few seconds and it gets the lines heated up without wasting a drop!!  MUCH better than running the tap into your drain, wasting precious fresh water into your preciously small grey tank, just to get things hot...

[Jeremy]

I like the daisy chain method for hot water.  Reason?  From each outlet or spigot  you can put a little valve that routes the hot water back to the fresh water storage tank.  When you need hot, open the valve for a few seconds and it gets the lines heated up without wasting a drop!!  MUCH better than running the tap into your drain, wasting precious fresh water into your preciously small grey tank, just to get things hot...

Why would that not work equally well in a system where each outlet had it's own supply?

As it happens I've been thinking about using a return-line arrangement like this just recently; I think leading the return line from each outlet together to a single valve would work equally well as each outlet having it's own valve, and it seemed to me that this would make for a neater installation - although possibly less convenient if your outlets are a long way apart.

Jeremy

[Chaz]

I like your idea about the return line Boogie and have contemplated that for if/when I get concerned about precious water. Right now it's not a big deal. And I think that would be the best of both worlds Jeremy.

This is a good topic as I have an issue with everytime the pump kicks on, while I'm in the shower, it changes the water temperature in a BIG way!!    Not good. (there is a lot of "dancing" going on in there  ) I was thinking putting the H2o heater closer to the tank would probably help. Actually, a little "re-plumbing" would probably help. It's all Pex and easy to get to. Anybody have a take on which way to go?? I'll do what it takes to make the shower stay a constant temp. 

If someone did had the time to do the different plumbing diagrams, I think it would be cool. But, I think most people can glean enough from Brian's description for the basic idea's. I just want to be SURE the shower gets priority with the hot water!  Brrrrrrrrrrrrr.........  The rest....... ehhhhh.
  Thanx,
    Chaz

[BG6]

Probably the better way is to home-run lines to each usage point from manifolds located at the water source.  More even distribution of flow and pressure, easy to manage, easy to  isolate and fix. 

How do you figure that?

Your water flow and pressure are dependent on the SOURCE.  If you are running park mode, you are limited by the inlet hose diameter.  If running a pump, the limit is the pump throughput.

Either way, you're not going to see any difference between daisy-chaining and running from a manifold.

The watchword for water OR electrical is "short and fat."  Short isn't an issue -- the long run of a daisy chain in a coach is going to be about 15 feet.  So that leaves fat.  Use 3/4" tubing and you are exceeding the diameter of your inlet hose or your pump outlet, so you can't do any better than that.

[kyle4501]

My factory built Airstream trailer has 3/8" poly tubing daisy chained (And, from the looks of it, they were paid by the fitting used!  ). All the fixtures are low flow, so the fixture has more restriction than the supply to it.
Wouldn't a temperature compensating or pressure balanced shower mixing valve compensate for changes in water pressure?

If you're concerned over volume used, you will be best served by using smaller lines & the ultra low flow fixtures. The smaller the line, the less water is used when waiting for hot & the less hot water is left in the line to cool off.
It is a shame that finding good fixtures (that make efficient use of limited water) seems to be luck of the draw.

My current desire is to have home runs for each circut that gravity drain for winterizing.
I'll plumb the manifold hot & cold supply so that they are as equal flow as possible & then run the hot & cold together so there won't be a need for the special shower valve.
I'll probably include a hot bypass to the fresh tank to save water at each station - it too will be properly sloped to allow for easier winterizing.

Since I'm using pex, I was considering running plastic conduit to run the pex inside - then if I need to replace it, it will be easy.
If it burst (because I forgot to winterize  ), the wet mess will be better contained.
It will be better protected from stuff rubbing against it (maintaining a drain slope will likely place it in some potentially abusive locations).

The advantage of a manifold system is you can select which circuts are used - may be usefull if you want to isolate one fixture. I'm thinking it may clean up the plumbing under the sink too. (But, if you need to shut off the supply to a fixture, you're going to have to do it at the manifold, not the fixture.)

YMMV

[Jerry32]

I too prefer the daisy chain style. I also designed mine to have all plumbing downstairs to be in one bay only so that heat in freezing weather is easier to handle. I put a mainline shutaff valve in the closet where I can get at it if I want to cut water supply without going into the bays. I also have a self regulating pump that varies speed so that there are no pulsed in the water flow to change the water temp. Jerry

[gumpy]

Well, I signed up to write the article on fresh water systems for BCM, but unfortunately, I haven't made much progress on it yet. However, keep the suggestions coming on this thread, because you can bet I will be including some of this information when I get to it this fall.

craig

[Brassman]

I don't believe that PEX will burst if frozen. I've used polybutlyelene, and the the only freeze problem I had is that the fittings loosen, but not break, on a hard freeze. Don't think that'll happen on crimped PEX.

[DMoedave]

Pretty sure George Myers who was a main contributor for a long time to the mag has a plumbing book. Look under Epic Conversions or you can find it on the Busnut board. Just re did our coach in pex.

[rv_safetyman]

We used the Manabloc system:  http://www.houseneeds.com/shop/plumbing/pexplumbing/vanguard/pexmanifoldsmain.asp .  We used the model MXBD14-2 which has 6 hot and 8 cold.  I use one of the valves to flood the washer drain to keep the "P" trap wet.

I really like the concept of multiple lines, as I can shut one off if there is a problem and the rest still work.  I had thought about building my own valves, but I could not begin to buy the parts for what I paid for the valve ($99 at the time - now $131).

Jim