City Water Circuit vs Electric Pump Water Circuit

The friendliest place on the web for anyone with an RV or an interest in RVing!
If you have answers, please help by responding to the unanswered posts.


New member
Nov 13, 2012
I recently acquired a used 2006 FR Surveyor SV264 and this will be my first time ever to winterize an RV so here's my question.  I've been reading the previous posts on the proper way to winterize and I've read where some people use compressed air while others use antifreeze and others do both but no one has explained to my understanding how all of the water lines are protected by using either the city water connnection to hand pump the antifreeze into the lines or choosing to use the inlet side of the pressurized pump located inside the TT.  If say I use the hand pump with the city water connection to winterize the lines won't that leave the electric pump and its inlet side water line unprotected and vice versa if I use the electric pump and install a pump converter kit so as to siphon the antifreeze from the gallon jugs will that backflow into the city water supply tubing?  Also since I have easy access to an air compressor if I decide to use compressed air to clear the lines first is there an attachment that I can use to clear the p-traps as well before I add the antifreeze and what would be the psi setting for the waste lines? 
There is only one set of water lines in your trailer.  The difference is where your fresh water comes from.  Basically about three feet of tubing is all that is different.  When the pump is on and drawing water from the tank it pressurized the entire system up to the check valve at the city water inlet.  When you are connected to city water, it pressurized the entire system after the check valve at the water pump.  Using the city water inlet, use compressed air at no more than 40 PSI to blow out all the lines.  Then if you want to, using the winterizing position if you have one use the pump to draw antifreeze into the lines.  Pour about a c f antifreeze into the "P" traps and toilet bowl and you are done.
The city inlet and the pump+tank feed the same plumbing, so the only difference is the pump itself and the line to the tank. When using compressed air only, you have to drain the tank and run the pump to clear it of water. The inlet side to the pump is an open line that drains back into the tank.  Alternatively, you could use RV antifreeze in the tank and pump a bit into the pump before blowing out the rest of the lines.

A small amount of water in the bottom of the fresh tank is not a concern, since it has plenty of room to expand. Freeze damage occurs when the expanding ice has nowhere to go, thus breaking the surrounding pipe or fitting.

You do not use air on the waste lines and P-traps. The waste lines(except for the traps) will drain and you pour a bit of antifreeze into the traps. There is no point to blowing out the traps before adding antifreeze. If the traps are dry, you don't need antifreeze. If the traps have water, then the antifreeze protects them. It's always best to have water in the traps anyway - that's what keep smells and insects out of the rest of the system
Watch out for any water filtration system you might have installed.  If there is a filter after your shore water hookup and you use antifreeze from the pump it'll never reach that filter.

Fortunately for me, I don't have to winterize this year but when I do I use compressed air at the shore water hookup (after removing my filter element) to blow the lines out.  I then open my low point drains and clear them and finally I use the pump to circulate anti-freeze throughout the system.

Anti-freeze is CHEAP.  If you freeze a water line somewhere under the floor and rupture it because it wasn't properly winterized the expense of tearing out plumbing that was installed during manufacture is going to be painful.
Thanks for the comments.  I'm lucky in that this TT doesn't have a filtration system other than an external one I manually add in the supply line coming into the city water connection.  As far as purging the waste lines I was worried that with the rv antifreeze already being at a 50% mixture that just pouring some down the drain wouldn't displace all of the standing water in the trap and would be more apt to freeze with the diluted mixture of antifreeze.  I've ordered a pump converter kit but it hasn't come in yet and all I have is the hand pump kit so if I have to go with it can how long can I safely leave the pump running to clear the water from inside the pump and what happens to the water just past the outlet side of the pump when I'm trying to purge the lines with air, won't the air just force the water back against the check valve at the pump or is the water such a small amount that it will mix with the antifreeze being pumped in thru the city water connection and not prove to be an issue?
The water that the pump moves doesn't lubricate the pump itself so running it dry won't hurt it but there isn't any need to run it dry for more than 15 seconds or so.

As far as your pump converter kit, all you need to do is "T" into the fresh water pickup line from the tank and install a valve to isolate the fresh tank and one to isolate the line that you "T" off from the pickup.  When you want to winterize you simply close the valve between the pump and the fresh tank then open the valve on the line that "T's" out of that line and stick it into an anti-freeze bottle.  This will pull anti-freeze through your pump without having to put 6-10 gallons of anti-freeze into your fresh tank.

I typically use about three gallons of anti-freeze and I probably am using more than I need to.  By running it through the lines it will automatically put more than enough in the P traps.  Don't forget the shower and especially the toilet.  The main reason I don't rely only on compressed air is the toilet valve only needs a tiny bit of water to freeze and break something.  Some of us have learned this the hard way.
The picture
City water---|
. . . . . . . . . .T fitting---Rest of RV
Water Pump-|

Hope that turns out,, As you can see there is but one water system, the two connect together.

To completly winterize you can simply open the low point drains, blow out the lines from teh city side, run the pump (Sucking air) to blow out that line, (Dont' forget to drain the pump-inlet strainer housing) then blow the lines again and again and again and again from teh city side (Several blows are needed) dump waste tanks, add pink to traps and toilets (enough to get it into the gray tank and flush pink down the toilet one time) and job done.

Come spring, you don't have to flush the pink out of the water lines (Major job in some rigs) and as for what's in the traps and toilets..... Well the latter you "Flush" every time you use it  (Same for the former for that matter) you do not worry about that, it goes on first use.
John From Detroit, You mentioned draining the pump-inlet strainer housing, is this a simple process? 
Stingingfork said:
John From Detroit, You mentioned draining the pump-inlet strainer housing, is this a simple process?

I'll chime in here even though the question wasn't directed at me....

Normally you can clear it simply by letting the pump run for ten seconds or so but if not the answer depends  upon where the rocket scientist at the manufacturer put your water pump, I've seen some that appear to have been installed before the cabinets were put in.  If you can get your hands on it then it's not hard to do.  The clear cover on the pump inlet sightglass theoretically unscrews or is a bayonet depending on model.  They do tend to be VERY stubborn to unscrew and yarding on it too hard will break the thing right off the pump.  I would recommend pulling the release fork that holds the entire sightglass assembly onto the pump and pull it off so that you can use two hands on it to unscrew the sightglass.

Even if you "can" clear the pump by just letting it run it's not a bad idea to clean or clear that inlet screen that's inside the sightglass once in a while, especially if you're not filtering your water prior to filling the fresh tank.
I see the question has been answered,, Yes, if you can get to the pump it is an easy task.

NOTE that that inlet strainer is an option, It is not "Built into" the pump thus it is possible you don't even have one.

It is a round plastic thing about 1.5-2" in diamater usually right at the pump's inlet, a quarter turn openes it, the hard part is lining up the tabs when you put it back together (A bit like hooking up ye-old 3" Hose, and roughly as hard to do).
I checked and there's not an inlet strainer on my pump but while I was looking I found a "T" valve so I could redirect the inlet flow and siphon the antifreeze into the water lines.  It worked great and now I'm set for the winter.  I did make one mistake by not setting the bypass valves on the hot water heater before I started so I had some go into the tank before I realized my mistake and corrected it but I will flush that out with the rest of it in the spring.  Thanks once again for all of the helpful comments! 

Latest posts

Forum statistics

Latest member
Top Bottom