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-   -   Advice Designing Water System... (https://www.skoolie.net/forums/f50/advice-designing-water-system-14580.html)

BusFiend 08-02-2016 04:33 PM

Advice Designing Water System...
 
Hey folks!

I'm in the process of designing skoolie subsystems and looking for some advice. I will be full-timing and am starting out with fairly high expectations that I'm sure will be tempered...

I'm looking at four wet areas in my design: kitchen sink, bathroom sink, shower and (probably) outdoor shower/hose. Bus will be plumbed with PEX throughout. (Toilet will be of the composting variety.)

I'm including on-demand LP heating.

What is the best and/or most efficient way of designing the plumbing to bypass 12v pump(s) when hooked to shore water?

I've read that the affordable tankless LP water heaters (eccotemp, Marey, etc) are particular about water pressure. Some are installing multiple pumps; one cold, one hot?

Advantages/disadvantages to including a pressurized bladder/tank to feed the bus? How big of a bladder/tank? Requires different pump(s)?

Thanks for your feedback!

BusFiend 08-04-2016 10:40 PM

After more research, I was able to find the following schematics. A filtration system can be added. Blackwater can be deleted if going with a composting toilet.

Basic:
https://www.skoolie.net/attachments/p...60e5ee0781.gif

Fancy:
https://www.skoolie.net/attachments/p...ee7492f5b7.gif

Peter B 08-05-2016 07:58 AM

I like layout and may steal parts of it for my conversion. One thing I'd reconsider is a composting toilet. If you have a black water tank why go with a composting tiolet. I'd rather flush it and forget then have to deal with hauling the waste through the bus for disposal.

How big are you going to make the grey water and black water tanks?

Thanks,
Peter B

BusFiend 08-05-2016 11:31 AM

I've definitely decided on the composting toilet. I'll be full-timing and plan on dry camping at least half the time. Solar power will make food and water (supply and waste) the deciding factors on length of stay. Besides, I'm looking at a 30ish foot skoolie, which limits undercarriage space. Composting is also a much simpler system and further reduces potential "system failure". As I'll be soloing, a composting toilet will go a month or better between servicing. I also don't want to deal with possible black water tank vent odors.

Space and weight will be the limiting factors for fresh and grey tanks. Currently, I'm thinking a minimum of 100 gal for each. Fresh will go under the bed, grey beneath the chassis.

If I went with black water, it would be 30-40 gal.

BusFiend 08-05-2016 11:36 AM

I'm still trying to determine the benefits of the expansion tank. Also wondering how to implement hot water recirculation to limit fresh water waste.

Peter B 08-05-2016 11:44 AM

Quote:

Originally Posted by BusFiend (Post 157874)
I'm still trying to determine the benefits of the expansion tank. Also wondering how to implement hot water recirculation to limit fresh water waste.

If you are using an instant hot water tank I'm not sure you'd need an expansion tank. You may want to just install a pulsation dampener and they are fairly small, about the size of a spray paint can.

leadsled01 08-05-2016 11:46 AM

you need a vent on the fresh water tank.

BusFiend 08-05-2016 11:56 AM

Quote:

Originally Posted by leadsled01 (Post 157876)
you need a vent on the fresh water tank.

Yes! All tanks must be vented. :Thanx:

BusFiend 08-05-2016 11:59 AM

Quote:

Originally Posted by Peter B (Post 157875)
If you are using an instant hot water tank I'm not sure you'd need an expansion tank. You may want to just install a pulsation dampener and they are fairly small, about the size of a spray paint can.

Good point. :Thanx: I'll put this on the further research list.

bread519 08-05-2016 12:06 PM

Quote:

Originally Posted by leadsled01 (Post 157876)
you need a vent on the fresh water tank.

Why is this? And what type of vent are we talking? I have a sterilized 55 gallon plastic drum from a local ice cream factory I was going to use onboard for my freshwater, it already has a hole on top that I had planned on sealing

BusFiend 08-05-2016 12:30 PM

Tanks need to be vented to eliminate negative or positive pressure when drawing from or filling.

Jolly Roger 08-05-2016 01:48 PM

Think of the tank and vent like this.
The tank is full of air so when you start putting water or waste in a 50-gallon(for example) you will only be able to get about 30 gallons into the tank because you are compressing the trapped air and it will create a back pressure that will stop the tank from accepting the full capacity of water/waste. A vent on a tank serves two purposes one for filling as described and for draining cause if the tank can't breathe/intake air when draining you will start getting a chugging effect like you experience when trying to pour water out of a milk jug,old style gas can or bucket with a pour spout and you will be at the dump station 3x as long waiting on your tank to drain.
The expansion tank is always a good idea in my mind but think about it like this?
Another name for an expansion type tank is a bladder type storage tank.
For example installed in this manner
If pump pressure is 65psi with a expansion/storage tank inline the pump will pressurize the storage/expansion tank (an extra 5-10 gal.) with a PRV(pressure reducing valve) installed downstream of the tank set at 50 psi.
Now the pump has to only pressurize the tank and your system feeds off of the extra 5-10 gallons of higher pressured storage.
Therefore your pump will only run full time when you are taking a long shower/tub or running a water spigot
Add an expansion/bladder type storage tank and save your pump some life and you won't have to hear everytime you get a cup and f water or fill the sink.
Just my opinion and some food for thought.

BusFiend 08-05-2016 04:05 PM

Quote:

Originally Posted by Jolly Roger (Post 157892)
Just my opinion and some food for thought.

Thank you for your thorough explanation! It makes so much sense. It evens out the water pressure and flow and reduces pump wear.

Do you think a bladder/expansion tank addresses any concerns of the finicky on-demand water heaters?

Tootalltechie 08-05-2016 06:56 PM

Just thinking out of the box. A 50 gal pressure tank (fresh water) pressurized by air or city water when connected.

Sent from my SM-G530W using Tapatalk

Jolly Roger 08-06-2016 09:47 AM

Depends on what the heater is picky about?
If it water flow then probably not and if it water pressure then probably not.
The pump is going to move the same amount of water whether it is doing it at 10 psi or 50 psi.
Never had an on demand heater?
To make the heater happy I would think that the piping size needs to be adhered to to give the heater proper flow.
A return line system defeats the purpose of an instantaneous heater purchase?
In my opinion

ol trunt 08-06-2016 12:15 PM

The instant hot water heaters are only instant if they are located immediately at the spigot they serve. The further away the spigot, the more water is sent down the drain while waiting for hot water to arrive. That is no big deal if you are hooked to city water but if you are boondocking it is as many gallons of water are wasted waiting for the hot water to arrive.

Also, because instant hot water heaters require both water pressure and water flow to operate the heater cycles on and off with each cycle of the spigot. This results in a choppy mix of either too hot or too cool water at the spigot.

By utilizing an electric solenoid water valve which directs hot water flow back to the water tank you eliminate waste of water and achieve an even flow of pretty constant temperature water at the spigot regardless of its distance from the heater. If you wish maximum flow of hot water (3 gal/min in my case) switching off the solenoid valve directs all the water flow to the spigot.

In my experience water seems to be the limiting factor when it comes to boondocking so anything that can be done to conserve water use becomes important. I've yet to use up my propane supply before running out of water but I suppose it could be done if one tried hard enough. I wrapped the hot water pipes leading to the various spigots with foam insulation but left them bare on the return line to allow the water to cool before going back into the fresh water holding tank. Jack

Tango 08-06-2016 12:38 PM

Several of the folks I know who live with tankless water heaters always capture whatever cool water comes out and use it for other things. One even pours it back into his tank.

BusFiend 08-06-2016 12:49 PM

Quote:

Originally Posted by Tango (Post 157955)
Several of the folks I know who live with tankless water heaters always capture whatever cool water comes out and use it for other things. One even pours it back into his tank.

As I've combed through forums, this seems to be the general solution to the problem. A few posters have briefly discussed recirculating water but never to the point of describing the system or mentioning specific equipment. I suppose for those only spending a few weeks a year in their RV, catching the cool water for other purposes is just fine. For full-timing, I would think a recirc system would be desirable.

BusFiend 08-06-2016 12:52 PM

Quote:

Originally Posted by ol trunt (Post 157951)
In my experience water seems to be the limiting factor when it comes to boondocking so anything that can be done to conserve water use becomes important. I've yet to use up my propane supply before running out of water but I suppose it could be done if one tried hard enough. I wrapped the hot water pipes leading to the various spigots with foam insulation but left them bare on the return line to allow the water to cool before going back into the fresh water holding tank. Jack

Thanks, Jack! Agreed. This is what I was thinking of. Now to find the components and work into a system design.

ol trunt 08-06-2016 01:47 PM

BF, here it is, $7:

1 2" 12 Volt DC Electric Solenoid Valve N C Plastic Body Water etc DDT CS 12VDC | eBay


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