Adding a "check valve" on a water pump

[crstrm]

Hi,

 

I have a couple of questions regarding the placement of a check valve on a water pump.

 

I noticed water within my fresh water tank when it should have been dry. That, I believe, is a good indication that the check valve within the water pump is not working properly. I have a fairly new Shuflo water pump.

 

So, I would like to verify a couple of things.

 

1. The check valve should go on the hose coming from the fresh water tank.

 

1. The arrow on the check valve should be pointing towards the water pump.

 

1. The hose coming from the fresh water tank also has the typical switch for winterizing. Does it matter if the check valve is place before or after the switch?

 

Thanks for your assistance.

Art SKP 87272

 

[skp51443]

Rather than adding a second check valve I'd suggest you open the pump up and clean it. A lot of the time a back-flow problem is a tiny bit of material picked up from the fresh tank and stuck in the pump. Worst case I'd replace the pump head, keeping the original motor if the cleanup didn't fix things.

On your first #1 I'd put the check valve on the pressure side of the pump, not the suction side. On the pressure side it takes the pressure off the pump.

Second #1, on the check valves I've seen you install them so the water is flowing in the direction the arrow is pointing.

Last #1, if you put the check valve in the suction line I don't think it makes a lot of difference.

As to the multiple #1's in your post the silly forum can do that to you when you try to the numbered list tool.

 

 

[crstrm]

Stan,

 

Yes, I was using the “numbering tool” from Word. I’ll remember to number my questions manually next time.

 

Just so that I’m clear on the terminology –

Pressure Side is the hose going from the water pump to the inside of the rig

Suction Side is the hose going from the fresh water tank to the water pump

 

You are suggesting that I put the check valve on the “pressure side” and the arrow pointing to the inside of the rig.

 

OK assuming that I have that correct; I did install the check valve on the pressure side and the arrow pointing to the inside of the rig. I turned on the pump (a replacement I keep) and no water went into the rig. I removed the check valve and water started to flow. Any thoughts?

 

Thanks for your reply

Art

[ronmon]

Stanley.... I'm confused. For an external check valve to prevent backfilling the tank, a check. valve would go in the line between the tank & the pump with the arrow pointing toward the pump, wouldn't it? if so, isn't that the suction side?

Like i said, I'm probably confused, but that's how I remember doing miine.

Ron

[Bobi and Dick McKee]

Art, got water in our tank when it should have been empty. I discovered the valve on our Hitch Hiker that used to direct the water to fill the tank or pressurize the rig was slightly, I mean very slightly, not turned all the way to pressurize the rig and it slowly allowed the tank to fill. Just a thought.

[Darryl&Rita]

The problem with putting a check on the suction side is the slight restriction it causes. Imagine sucking on a straw with it pinched slightly. That's effectively what you're doing. It has less effect on the pressure side.

[crstrm]

Dick,

 

Good thought, I’ll have to keep that in the back of my mine. However when I filled the fresh water tank and then turned on the water pump the motor hummed but no water went into the rig. I switched water pumps (I keep a spare) and water started to come out of faucets.

 

I have already replaced 3 Shurflo water pumps because the same issue. I figured that it was time to put in a check valve to finally (hopefully) correct the problem.

 

Thanks for your comments

Art

[crstrm]

Darryl,

 

Just want to clear up some terminology.

 

You are suggesting that I put the check valve on the hose that goes from the water pump to the inside of the rig and the arrow pointing to the water pump?

 

Or should the arrow point to the inside of the rig?

 

Thanks for your feedback

Art

[Darryl&Rita]

The arrow points in the direction of flow. Always.

[skp51443]

Stan,

 

Yes, I was using the “numbering tool” from Word. I’ll remember to number my questions manually next time.

 

Just so that I’m clear on the terminology –

Pressure Side is the hose going from the water pump to the inside of the rig

Suction Side is the hose going from the fresh water tank to the water pump

 

You are suggesting that I put the check valve on the “pressure side” and the arrow pointing to the inside of the rig.

 

OK assuming that I have that correct; I did install the check valve on the pressure side and the arrow pointing to the inside of the rig. I turned on the pump (a replacement I keep) and no water went into the rig. I removed the check valve and water started to flow. Any thoughts?

 

Thanks for your reply

Art

 

You should be able to blow on the check valve and confirm the direction it is going to allow the water to flow.

 

Stanley.... I'm confused. For an external check valve to prevent backfilling the tank, a check. valve would go in the line between the tank & the pump with the arrow pointing toward the pump, wouldn't it? if so, isn't that the suction side?

Like i said, I'm probably confused, but that's how I remember doing miine.

Ron

 

Yes that is the suction side but that isn't always a good place for the valve as the suction side is not always built to withstand the water pressure you see there when using city water and with a leaking pump.

 

The problem with putting a check on the suction side is the slight restriction it causes. Imagine sucking on a straw with it pinched slightly. That's effectively what you're doing. It has less effect on the pressure side.

 

That can be a problem if the check valve has a strong spring in it that resists opening.

 

Dick,

 

Good thought, I’ll have to keep that in the back of my mine. However when I filled the fresh water tank and then turned on the water pump the motor hummed but no water went into the rig. I switched water pumps (I keep a spare) and water started to come out of faucets.

 

I have already replaced 3 Shurflo water pumps because the same issue. I figured that it was time to put in a check valve to finally (hopefully) correct the problem.

 

Thanks for your comments

Art

 

Your initial lack of flow with the first pump could have been from a loss of prime due to the internal leak.

 

If you replace a pump that isn't really old, many rigs never have the pump replaced before they are scrapped, you likely have a different problem. If you have replaced three pumps you almost surely have a problem that is killing the pumps, not just the world's worst luck in buying three bad ones in a row.

 

I'd suggest looking for the source of the problem, more than likely debris in the fresh tank getting sucked into the pumps and killing them. Pump clearances are tight and it does not take much to slip into a sealing surface and cause backflow, loss of prime or low pressure. Flushing the fresh tank is often ineffective due to the small drain and lack of access but you still should try it. Sometimes a bit of creative plumbing and a wet/dry shop vac can get the crud out of the fresh tank, use lots of water and dump the vac into a pillowcase or something so you can see what it is sucking up.

 

An alternative to tank flushing and something I'd consider is adding a filter to the suction line, a clear one that you can monitor for debris with a cleanable/replacable element would be a very good idea. I don't like this one much due to the coarse screen but it is an example of what I'm talking about.

 

http://www.campingworld.com/shopping/item/universal-water-filter-threaded/75852

[Darryl&Rita]

I agree, Stan. I'm more used to dealing with larger pumping systems, where all the reductions in suction supply need to be calculated out to meet the pumps NPSH. As most RV pumps are above the water tank, I thought it worth mentioning the effects of restricting the suction.

[crstrm]

I am already using a filter on the water pump. I've checked it several times and it's clean.

 

So it seems that I should be adding a check valve on the "pressure side" (from the water pump to the rig) and the arrow pointing to the rig.

 

I thought I tried that but perhaps I had the arrow going in the wrong direction.

 

Thanks Bill for the clarification.

 

Stan,

You mentioned that I should try to clean the water pump. Where is the internal check valve on a Shurlo?

 

Thanks

Art

[rockintom]

Y'all are making this too complicated. As most know the old Shurflo Classic 2088 3 chambered pump had a small weak-ass check valve. I've gone thru 5 in 3 years. I got where I could do the job in 20 minutes! Kept 2 in stock all the time! Anyhow you have a choice of continue replacing them periodically, or put in a new Shurflo 4008 or 4048 - 4 chambered pump. The sealing surface area of the new pumps are much more robust. My 4048 is going on a year old with no issues. Of course use a strainer on the suction side of the pump to prevent small stuff getting into the pump/check valve. Simple, fairly reasonable solution.

[skp51443]

Here are the newer four chamber pumps: http://shurflo.com/rv-products/rv-pumps/rv-fresh-water-pumps

 

Looking about I found this strainer with what I think is a finer screen than the link above: http://shurflo.com/rv-products/rv-accessories/rv-water-system-accessories/rv-strainers/112-twist-on-water-strainer-1-2-pipe-inlet

 

If you aren't finding anything in your existing filter then I'd not hold out much hope for a fix by replacing it unless it has a really course filter element.

 

The check valve is built into the pump head, when you crack it open just clean everything and run a fingertip over all the sealing areas to see if you can feel any rough spots. You can also buy a rebuild kit (if they still make them) that is a lot cheaper than a replacement head or a whole pump.

 

PDFs with pictures that should help you service your pump, even if not an exact match to your model: http://shurflo.com/rv-products/rv-education-center/193-rv-product-manuals

 

Conversion kits and and parts for old models: http://shurflo.com/rv-products/rv-pumps/rv-fresh-water-pumps

[crstrm]

I am currently using a Shurflo 4008 and had nothing but problems with this model.

 

Stan, do you think that adding a check valve could solve the issue?

 

Thanks

[skp51443]

It would solve the backflow problem and if you put it on the pressure side of the pump also prevent any issues from the pump leaking while on city water.

 

I'm still scratching my head over the multiple failures when you have a filter in the suction line, something I've never seen before.

[rockintom]

Stan, the check valve on the pressure side would prevent the shore water flowing back thru the pump into the fresh water, but when you are on the pump (no shore water) and the pump residual pressure leaks passed the check valve and drains back into the fresh water tank, causing pump cycling like you had a external leak. Think you'd hafta have a check valve on the fresh water (suction) too, to correct a leaking check valve.

 

After thinking about it.......wouldn't just installing one check valve in the suction side would fix both issues?

[rockintom]

Cars, are you positive you have the 4008 Shurflo? I ask cause you have an older rig and unless you've replaced the pump recently, you might have the older model pump. Just saying....the 4008 hasn't been out that long. All of the 4 chamber style pumps use the same basic head assys/check valves. They have not be an issue like the old jobbies did. If you can see the old style and newstyle check valves side by side.....there's quite a bit of difference. Just asking. rockin'

[skp51443]

The check valve on the pressure side might cause some pump cycling, how much and how often is hard to tell but that leaves the pump head under pressure when hooked to city water and if it is having leakage issues I'd not want to do that. The choices you have to make with an external check valve are why I'd keep that for a last resort.

[Yarome]

If you don't already have one, a good quality filter should be inline on your external water source as well as a pressure regulator (Actually on sale at the moment at camping world for just over $40 I think. You can't beat that price for an adjustable reg.) Also, it's not a bad idea to have a shut-off valve on your hose leading into your rig when you're on city water. You will also want to run the water for a bit before actually attaching it to your rig. It's possible to pick up contaminants in the hose itself that will blow back into your system. That might be one possible reason your might be getting debris in your water pump.

 

I agree with Stan on the placement if you are going to shtick in another check valve. It will take the pressure off of your pump when not in use, but don't forget to cycle it from time to time even though you may be on city water. It will keep your pump 'fresh' and primed. A dry pump wears out considerably faster than a pump in regular use.

[TXiceman]

When I have a pump check valve go bad and back back-feeding water in to the fresh water tank, I put a manual ball valve in the line and just close it until we are off city water and need to use the tank. Never a problem again.

 

Ken

[Bobi and Dick McKee]

In our former life as sailboaters we did a ton of testing for Catalina Yachts. They finally gave up on Sureflo pumps and went to Jabsco. When we purchased our new HH the we went through 2 Sureflo pumps in 6 months. We installed this Jabsco pump and have not to think about it in 4 years. Great pressure and great flow. I know it is a little pricey but it works. Just a suggestion.

 

http://www.westmarine.com/buy/jabsco--par-max-plus-freshwater-pump-12v-16a--12884599

[tinstartrvlr]

Dick,

Like your recommendatioin on the Jabsco pump-having been around sailboats a bit I know sometimes it's worth the extra money to get quality. I was reading the specs on the pump and noticed it draws 15amps! at 12v. Your thoughts about that? Seems like an awful drain on the battery, especially since in my case I only use it when boondocking.

[Bobi and Dick McKee]

That 15 amps is only for the few moments the pump is running. Admittedly we had 1200 amp hrs. of batteries on the boat, but we only have 4 6v batteries on the HH. If you shower like we do when dry camping by turning the shower off with a button at the shower head while soaping up etc. the pump probably runs less than 2 minutes per shower. We have 4 6v batteries and can dry camp for about 3 days before needing to fire up the Honda and re charge. If you are in the cold my opinion is that the heater will drain the batteries faster than you will with water pump.

[crstrm]

Rockin - Yes, I do have a 4008 water pump by Shurflo. I think that I have replaced 4 water pumps over the past 2 years. Interesting that the original water pump still works.

 

Stan, I placed a check valve (SMP 18-902 T-1588) on the pressure side (hose going from water pump to the rig and the arrow pointing to the rig – AND NOTHING HAPPENED! The water pump did not make any noise and there was no water coming from the faucets. I removed the check valve and the pump started to work again.

 

Totally confused at this point. Do I have the wrong check valve? I have not tried to put the check valve on the suction side.

 

I may not be able to respond quickly to your posts for about a week. I will be going to areas that have very limited or no internet access at all. I’m moving tomorrow (Friday) and will probably have some internet access but after Friday for about a week I am not counting on any access.

 

I hope we can resolve this issue.

 

Thanks everyone.

Art