Water pump woes

[allscott]

I have a 99 Vanguard fifth wheel with what I assume is the original sure flo diaphram pump that I can't seem to get primed.  I had trouble last year but farted around long enough and once primed it worked fine.  This is the first time I have tried to use it this season. 

I hooked the camper up to a water supply and flushed the lines with that pressure.  I then Half filled the fresh water tank and tried the pump.  It tries and spits but I can't get the system to prime.  When I put the supply hose for the pump in a bucket of water it pumps just fine but when hooked to the holding tank supply line it just won't suck (my fresh water tank is below the pump, my bucket of water was above).  When I disconnect the discharge hose from the pump and turn it on it won't suck out of the water tank either.

My guess is that the pump is just shot and it won't create enough suction to pull water from the fresh tank.  I think if I could just get everything primed it would probably still work.

Any suggestions before I look for another pump?  Anything I need to know about a replacement pump? It looks pretty simple, inlet, discharge, and a pressure switch wired in series with the supply power.  I don't have a problem buying a new pump, just not sure I can get one in town quick and I  was planning on going camping Sunday.

As always, thanks in advance.

 

[Jim Dick]

Make sure any winterizing valve is NOT in the winterizing position. This happens a lot. 

 

[Molaker]

Check the fittings and hose very closely on the input side for cracks or other possible leaks that would prevent the pump from drawing adequate vacuum to pull water from the tank.  Remove them and reseal with some teflon sealer if necessary.

 

[allscott]

Check the fittings and hose very closely on the input side for cracks or other possible leaks that would prevent the pump from drawing adequate vacuum to pull water from the tank.  Remove them and reseal with some teflon sealer if necessary.

No winterizing valve in the one, the valve is mean moving hoses around when its time to winterize.

 

[allscott]

No winterizing valve in the one, the valve is mean moving hoses around when its time to winterize.

I will check the best I can.  The supply hose for the pump is only about 3 inches long before it goes into the floor and into the tank.  I have no idea what it looks like after it goes through the floor.

It makes sense that would be the problem though.  Taking the freshwater tank out doesn't sound like a fun job.

 

[Tombstonejim]

Are you sure it is not filling the hot water tank. It will now flow water untill it does.

As a last resort you could fit a tee just before the pump and add water to get it primed and pumping.

It does not hurt those pumps to run dry so you could try turning it on and opening all the faucets to reduce restriction and let it run for 30 minutes or so to see if it will pick up.

Fill the tamk all the way up to reduce the suction height.

 

[John From Detroit]

Two thoughts.. If you live where it freezes in the winter, Many folks do not remember to drain the pump inlet filter housing, It can crack and then suck air.

On my coach I will draw a short line diagram.

Tank--Valve-{T-fitting and dump valve}--Pump--House

Another poster somewhere, has the same hookup I do with the dump valve being "T"ed into the pump inlet.. He forgot to close the valve.

 

[allscott]

I have two 3 way valves to bypass the hot water tank.  When not bypassed it tries to fill the tank but can't. 

There is no filter on the inlet to the pump.  Just a flexible hose coming out of the floor to a fitting on the pump unless there is something under the floor that I can't see.

Thinking about it it has to be sucking air from somewhere but where?  I know this because when I pump out of my pail I can purge all of the lines but when I hook it up to the tank I start getting a bunch of sputtering again. 

I will fill the tank right full and try that.  I will also see if I can actually suck water out of the tank.  Going to need a couple fittings as I can't actually get my head in there to get at the suction hose.  I will also crawl underneath and see if I can see anything. 

Thanks for the suggestions so far, this certainly shouldn't be rocket science.

BTW this is my first RV of any shape so I really have no idea what a "typical" plumbing system in a camper looks like.

edit:  And yes I can T in another line fairly easily with a valve, I should do that anyway, that way I could run antifreeze in without having to disconnect the pump like I do right now.

 

[RLSharp]

Thinking about it it has to be sucking air from somewhere but where?

Sometimes when the water tank is prepared for installation, the holes in the tank are cut with a hole saw. If the slug from this cutting is allowed to fall into the tank, it can eventually make its way to the outlet of the tank and plug water flow out of the tank. I do not know how to check for this other than draining the tank and sticking a wire into the outlet. Just something else to keep in mind.

Richard

 

[R. J. Barton]

Make sure any winterizing valve is NOT in the winterizing position. This happens a lot. 

Ayup.  : Did this to my self this week while down at Roaring River SP. We don't use the pump much and I didn't have all the valves in the right configuration.  After futzing with it for over half and hour and wondering why it wasn't working I rechecked the valves, changed them to their proper position and had it working in about two minuets. 

Of course it may be sucking air some place which will impede its proper function too.

 

[Great Horned Owl]

The rubber diaphragms in those pumps harden up with age.  Once they get hard enough not to seal well, they will leak air and the pump wont prime. Diaphragm replacement kits are not very expensive and are fairly easy to install.

Joel

 

[RLSharp]

The rubber diaphragms in those pumps harden up with age.  Once they get hard enough not to seal well, they will leak air and the pump wont prime.

When I put the supply hose for the pump in a bucket of water it pumps just fine but when hooked to the holding tank supply line it just won't suck (my fresh water tank is below the pump, my bucket of water was above).

Why would the pump work with a bucket for it's source and not with a water tank as it's source?

Richard

 

[allscott]

I think I might have found the problem.

Where the inlet hose comes out of the floor it was sealed around the hole with RTV.  That seal is broken and I think I can feel air blowing by that gap when the pump is running.  I am going to try to reseal that hole again and go from there.

I'm confused as to how air would be getting into the system from there though.  I have no idea how this hose is sealed to the tank.  I'm starting to think at one point there was a fitting coming out of the tank through the floor and the previous owner Mcgyvered something into place.  I kind of doubt the manufacturer did this.

 

[Great Horned Owl]

Why would the pump work with a bucket for it's source and not with a water tank as it's source?

Richard

Because, as the OP stated, the pump was above the level of the tank, but below the level of the bucket.

 

[Molaker]

I think I might have found the problem.

Where the inlet hose comes out of the floor it was sealed around the hole with RTV.  That seal is broken and I think I can feel air blowing by that gap when the pump is running.  I am going to try to reseal that hole again and go from there.

I'm confused as to how air would be getting into the system from there though.  I have no idea how this hose is sealed to the tank.  I'm starting to think at one point there was a fitting coming out of the tank through the floor and the previous owner Mcgyvered something into place.  I kind of doubt the manufacturer did this.

If that fixes it, I'll be as confused as you.  That seal should only be there to keep insects & other small critters out.  In your troubleshooting, did you actually remove the input hose from the fitting on the pump?  If you can, try putting a new hose on there and run it into a bucket of water.  If the pump can pump in that comfiguration, put your finger over the end of the hose (in the bucket) and see if you feel a good suction.  If you do then I would expect your problem to be the feed hose or on to the tank.  Some day, some way, you are probably going to have to gain access to the top of the tank.  The hose may have a hole in it somewhere along its route to the tank or may not extend far enough into the tank.  Did you ever try filling the tank entirely to see what affect it had?

 

[allscott]

If that fixes it, I'll be as confused as you.  That seal should only be there to keep insects & other small critters out.  In your troubleshooting, did you actually remove the input hose from the fitting on the pump?  If you can, try putting a new hose on there and run it into a bucket of water.  If the pump can pump in that comfiguration, put your finger over the end of the hose (in the bucket) and see if you feel a good suction.  If you do then I would expect your problem to be the feed hose or on to the tank.  Some day, some way, you are probably going to have to gain access to the top of the tank.  The hose may have a hole in it somewhere along its route to the tank or may not extend far enough into the tank.  Did you ever try filling the tank entirely to see what affect it had?

Yea that didn't make any sense to me either and it didn't work either lol.

Yes when I was doing the test with the pail I actually pull the fitting of the inlet of the pump (its a 90 deg fitting with a barb on the end), and move that fitting to another hose into the pail and then hook it back up to the pump.  Pumps fine in this configuration.  Yes if I put my finger over that hose it seems to have suction but I really don't know how much to expect, it ain't a whole lot. 

I did fill the tank right full and it seems to work a little better than when the tank was half full.  The only explanation I can think of is the pump just doesn't have enough suction. 

I guess my next step is to try and pump out of a pail on the ground to simulate what the pump is trying to do out of the fresh water tank.  If the problem turns out to be with the suction hose or the tank then I have bad problems.  The tank is right above the axles...   

 

[Great Horned Owl]

Take the head off of the pump and replace the diaphragms. They're fairly inexpensive.

Joel

 

[ChiefM]

It sounds like the diaphragm is old and crusty and not able to pull from the tank.  Like Joel said- Take the head off of the pump and replace the diaphragms. They're fairly inexpensive. This will eliminate the pump and then continue troubleshooting further if that does not fix it.

 

[BigDfromTN]

Yea that didn't make any sense to me either and it didn't work either lol.

Yes when I was doing the test with the pail I actually pull the fitting of the inlet of the pump (its a 90 deg fitting with a barb on the end), and move that fitting to another hose into the pail and then hook it back up to the pump.  Pumps fine in this configuration.  Yes if I put my finger over that hose it seems to have suction but I really don't know how much to expect, it ain't a whole lot. 

I did fill the tank right full and it seems to work a little better than when the tank was half full.  The only explanation I can think of is the pump just doesn't have enough suction. 

I guess my next step is to try and pump out of a pail on the ground to simulate what the pump is trying to do out of the fresh water tank.   If the problem turns out to be with the suction hose or the tank then I have bad problems.  The tank is right above the axles... 

I think this is your best next step.

If that works,  Then check that hose all the way to the tank.  Im inclined to believe it is one of two issues.
1. The hose from the tank to the pump has a hole.
2. bad diaphrams on the pump.  This would be ruled out if it will pump from a bucket on the ground with a good hose.

 

[firehose]

These pumps have a built in pressure switch, and shut off at a certain pressure.  If the pump is not getting suction, it will keep cycling and stay on.  Does the pump keep trying when you turn it on? 

If so, and there are no leaks from the tank to the pump, it's probably a bad pump.  I'd replace it, in that case.  If that doesn't resolve the issue, you may have a blocked line somewhere.

To me the easiest fix would be to actually replace the pump first.  If that fixes the issue, great, if not, you could always turn the new pump in for a refund, or keep it as a backup. 

You can spend a lot of time tracking down water pump issues.  I've done it before, only to find it was a bad pump.  I could have saved a lot of time just replacing it in the beginning.