How to replace a compressor for a water pump?

[Trunkhill1]

I have a 1975 166 travel trailer that has a static 30psi air compressor for the fresh water tank.  It recently quit working and have heard that a water pump could be installed in its place.  Has anyone had any experience swapping one for the other?  Any specifications that I should use?  I would estimate the tank to be about 25 gallons.
Thanks,
Trunkhill1

[kenwautoone]

Most common water pump is shurflo 4008-101-A65.Amazon has them for $54. Last time I checked, camping world or any RV supply house.
You just need to look at compressor and determine which connect tion puts water into your sink/ toilet.hook up red and black leads to coach 12 volt battery.probably a good idea to put a fuse in there.....Ken

[Rickf1985]

The compressor only puts air into the tank. The water will come out the bottom outlet. You will need to tee into that outlet with your new electric pump and that will take care of the water pumping issues. Then you will have to address the filling of the tank. I don't know how those tanks fill but it will have to have a vent to let air out as the water goes in and also to let air in as the water level drops.

[TerryH]

The compressor only puts air into the tank. The water will come out the bottom outlet. You will need to tee into that outlet with your new electric pump and that will take care of the water pumping issues. Then you will have to address the filling of the tank. I don't know how those tanks fill but it will have to have a vent to let air out as the water goes in and also to let air in as the water level drops.
As always, my opinion.

Personally, I much prefer the electric pump over compressed air. It is an 'on demand' system that, with power to the pump will only kick in when you turn on a tap.
Compressed air depends on the tank pressure, which will always bleed down, causing the compressor to kick in.
As per Rick, the vent, vent hose size, vent hose routing and screen capping are all critical.
Too small, or a restricted vent line will result in the back up of water when filling your tank. Incoming water will be defeated by the minimal air exchange from the tank. Incoming water replaces outgoing air - ideally.
It is not difficult to achieve, And again, I personally much prefer the electric pump over air.

[tmsnyder]

Or use a tank of CO2 to push the water, you'll have seltzer water on tap!  And when washing dishes you'll have 'scrubbing bubbles' 

[Rickf1985]

Most modern tanks are gravity fill and have a port outside where the hose goes without a solid connection, hence "gravity" fill. You would also have the "city" water connection where you hook up to city water with a hose and use that directly in the coach without filling the tank. MOST modern unit, by modern I mean 80's on up, use both and you cannot fill the tank with the pressurized connection, only the gravity fill. NOW, That said, on my 31 foot Chieftain I only have a pressurized fill connection and that is how I have to fill my tank. There is a valve I have to open to direct water to the tank or close to direct it to the coach. This system is nice in one way and a pain in others. It is nice that I can hook up a hose and turn it on full force and walk away and 55 gallons later it comes out an overflow hose and I know it is full. It is a pain when I am boondocking and I have five, five gallon cans full of water and I cannot just pour them into the gravity fill hole to refill my tank. I have to break camp and take the whole coach to the water fill station. And if you say 55 gallons of water should last a long time you are right, it will last me two weeks but you do not know my wife!!! W% W%

[legomybago]

It is a pain when I am boondocking and I have five, five gallon cans full of water and I cannot just pour them into the gravity fill hole to refill my tank. I have to break camp and take the whole coach to the water fill station.

That's not a good design. I would change that rick if you could, add a gravity fill port. I'm not trying to hijack this thread to another topic

[Trunkhill1]

Ok so found the pump.  What would be the technical term for the air regulator which would allow air in and out of the tank?
Thanks!

[Rickf1985]

Vent

[Trunkhill1]

Would a 'fuel p-trap vent' (such as https://www.amazon.com/Attwood-90-Degree-P-Trap-Fuel-Tank/dp/B0000AZ7NN/ref=sr_1_4?ie=UTF8&qid=1498246625&sr=8-4&keywords=RV+water+tank+vent) work?
Trying to find one that will allow for air in/out without the water doing so.

[CapnDirk]

I'm curious why you need a vent.  How do you get the water into the tank?

[Rickf1985]

He is going to fill the tank through the original fitting which I believe did not have a vent anywhere since it was a pressurized tank. Trunkhill, You are going to want something that will allow enough air out so that it does not build up pressure as you fill it. Technically you should have a gravity fill which usually has a vent built into the fill and goes into a separate hole in the top of the tank. All you need is an open fitting with a hose on it going out the bottom to vent out the water when full. Otherwise you have no way of knowing when it is full. Where does the fill come into the tank and are there any now unused fittings on top of the tank that can be changed to a vent?

[CapnDirk]

Thanks Rick, now I understand.  The fill neck is also air tight?  got it.  Could that be adapted to just a hose (whatever diameter) and one of those outside water hatches?


http://www.ebay.com/itm/RV-CAMPER-MOTORHOME-TRAILER-OUTSIDE-FRESH-WATER-BOX-FILL-DOOR-/220992446996?hash=item33742d2214:g:298AAOSwAL9UhiIe&vxp=mtr


Don't know what size inlet/fill hose is used.  The supply to the MH would pass through the electric water pump from the tank.

[DaveVA78Chieftain]

From the filling perspective, the pressurized system had to have a fill and vent system also.  Far as I know, that would not change when converting to a pump based system.  The only thing diffferent is that the Air Bleed Fitting would always be left open when using the pump for a pump based system so that you did not pull a vacume on the tanks.  If connected to city water, you would close the air bleed so water is not forced out.

[Rickf1985]

Well, I don't have one of those systems and the last time I did was 35 years ago so I don't remember the line sizes but looking at Dave diagram above I am thinking it would be hard since the gravity fills use a 1 1/2 inch or 2 inch fill hose and that would have to continue all the way into the tank. You could never get enough water to gravity flow into the small lines you have on there now. Dave is the guy to talk to since he still has his.

[CapnDirk]

X2 on Dave.  Systems that just have a tank (newer stuff) also have a tube for vent.  Let air out when filling and equalize when draining.  Replace the vent valve with something open.  Fill tank slowly you will know when full when the vent line (now open) shoots you in the chest  .  The out going line to the motor home would get cut.  Tank side to in side on pump, out side on pump to motor home systems


Copper or plastic tube on the motorhome?  either way, once you have the pump find out the size of the tubing for the motor home and get creative at a plumbing or big box store.  A twelve volt toggle switch and some wire to the pump and your fine.  Also get an inline fuse holder (15 amp on mine) and use it at the pump so you know where it is.


Dave:  Thanks for the pic.  Always an education on the old stuff from your posts.

[DaveVA78Chieftain]

Actually, that picture is from the "Eyebrow" Winnebago Coach Service Manual

[Trunkhill1]

Got it, thanks all!
All i'll need to do is cap off one off one side of the compressor line T, because it's at the top of the tank and use the petcock valve line (previously used as the air pressure bleed line) that's sticking out of the bottom corner of the RV during filling or use at the campsite.
All I'll need to do then is wire the water pump to the 12V (which was previously fused), replace the switch, bolt it to the floor and hook up the lines. 
I'll be sure to post some before and after pics.
Again thanks everyone for making it all come together!
Trunkhill

[CapnDirk]

Trunkill:


You would be helping many people on the net and here to document and pic the procedure.  Lot of people wanting to or have had to do this.


Am I correct that you are going to use the power supplied to the compressor to run the new pump?

[Trunkhill1]

Trunkill:


You would be helping many people on the net and here to document and pic the procedure.  Lot of people wanting to or have had to do this.


Am I correct that you are going to use the power supplied to the compressor to run the new pump?

Affirmative, I am going to use the same 12V DC power.

[strykersd]

Although I'm sure the water pump on demand system has many perks, is it worth all the effort?  If I was going to build a system from scratch I'd definitely go that route, but if the pressurized system is in their already I'd work with what I have.  I was able to build a pressurized pump that kicks on automatically for just $40.

And if it helps, on my 71 Brave, the vent line is a schrader valve right by the fill port.   

[Trunkhill1]

Pics of the old compressor set up for the water supply system.  I previously replaced the solid copper pipes (which had burst and snapped in various areas) with braided washing machine line and the brass to adapt it.  I also added a ball valve on the exterior for the fill.

[Trunkhill1]

More pics of preparing for the new water pump install.

[Trunkhill1]

Final install and functional check 

[Rickf1985]

Nicely done. Is that a newer tank? The clean welds and no rust sort of looks like it is much newer than the coach.