View Full Version : Trailer plumbing

02-16-2011, 08:25 AM
I'm going to build a trailer for vending. I talked to my HD about my build and I wouldn't need any more license's for this venture.

She told me that I needed the standard 3 bay wash with the additional hand wash sink. We haven't talked specifics about sink size other then I need 30 galleons fresh water.

I'm good with the water tanks, the sinks and the gray water. How do you hook up the hot water heater and the pumps for fresh water.

Could some one help me with this and web sited to purchase from.

My HD inspector went on vacation today and I'm 2 month away from my build (trailer is behind a 40 foot snow bank). When she gets back I'll finalize the sink sizes and hot water requirements.


02-16-2011, 08:31 AM
Hey Rick,

I wouldn't go any less than 6 gallons on the water heater and normally the grey tank needs to be 10-15% larger than the fresh. (Depends per location and HD) You'll need to determine what you'll be powering the water heater with as well...electric or LP? Are you using a 12VDC pump of 110V? Good luck with the build.

02-16-2011, 09:33 AM
I would think this... youll want to close your eyes and envission this as I describe it... oh wait... if you close your eyes, you wont be able to read.... ok then....

From the pump outlet... to a "T" one side will go to hot and the other to cold... from the hot side of the T to the heater inlet... then the hot water out to your faucets.

Hrom the cod side of the T to your cold faucets.

Now, unless you are planning on using a small presure tank (befor the T) be prepared for the water pesure to drop if you yurn on mor than one faucet. (this is what I would reccomend doing... more cool down time for the pump)

Also, I would reccomend insulating your Hot water line to help retain the heat, and help your wash temps come out to code/regs.

Have you thought about an "on demand" water heater? They are a bit more pricy, BUT in the long run you wont be drawing down amps or using more LP than you need for the usage... Not haveing to KEEp it hot... also consider the fact when you are not powered up, you will have to expend EXTRA fuel/amps to RE heat the tank again.

by branching off the T to both the hot and cold, any time you use the hot, the pump will kick in to refill.

Im not sure about your State, but some states will even count the # of gallons in your hot water tamk as water storage, so make sure your gray water capacity (%)accounts for that as well.


RICK Allen
02-16-2011, 10:00 AM
If you are building your trailor have you considered putting the water tank in the roof and gravity feeding everything. also if you are having a gas fired stem tray then for yout hot water run 2 large copper tubes down each side of your burner, and uptight to the bottom of the steam tray to capture and retain the residual heat, I have all this in my cater truck and it works great no pumps to break constant hot water, so hot one has to be careful not to burn yourself, as it'll be at the same temp as your steam tray

02-16-2011, 10:03 AM
Good idea Rick, what is the recovery time for the hot water?


RICK Allen
02-16-2011, 10:04 AM
Opps forgot you'll want to put a 1 way valve between your water tank and the tubes so the hot water can't migrate back to the tank, sorry for the spelling in the previous mess.

02-16-2011, 10:08 AM
What about a presure relief valve? if your faucets are closed, and you have a check valve from your tank... that could become "explosive".. the heated water creates/builds up presure, and nowhere to go.
Dont get me wrong, I like the idea very much, but looking at the safety aspect of it in addition, and what can be done to mitigate any accidents. Unless your using it as a pre heater for a HW tank (then you might need 2 chck valves...dunno)

RICK Allen
02-16-2011, 10:09 AM
If the burner, which is dictated by the steam tray temp is on about 5 min, should have mentioned as well a hot water tank pressure relief valve is wanted after the oneway valve as pressures can build up quite high if I'm not using my hot water the valve blows when it gets too high

RICK Allen
02-16-2011, 10:18 AM
Of course, when doing this the hot water pipes should be copper, normal compression fittings seem to work fine, for the joints and also ease of removal in case of a leak, occurring

RICK Allen
02-16-2011, 10:25 AM
Also what really makes the HD happy and I think it is mandatory in Cal. is to put a few hose bibs inside and dedicate a potable water hose inside to fill everything that needs water inside there for eliminating the need to bring an outside hose inside