Interior Water Pump Shurflow 4009 4048 Adjustment for back-flow pressure, NRV

Lap Dog

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I saw relatively recent thread concerning problems with the water pump. Also looking at other Forums there seemed to be quite a lot of misinformation and confusion concerning location of NR Valves and their operation. I had my own issues and decided to have a crack at fixing it. These valve adjustments (located at the front of the pump) fix the following issues:

Backflow (Bypass) valve:
Mains water filling tanks
Air in water system (spitting taps)
Pump constantly running
Pumps appearing to operate in reverse (pumping to tanks)

Negative Head (pressure switch) valve:
Pump constantly running
Pump running on and off
Pump oscillating rather than running somoothly
Pump not running
Shower running hot and cold

Warning: I am not a plumber and have come with this information 'half-baked' in order that somebody will add to further information to make this more complete/useful/accurate.

I took off the pump and had a look a it's gizzards but this is not necessary. The only thing I found/confirmed by doing this is that the factory has no concept of correctly torquing fixings. Any screw torqued correctly is purely by accident. The only thing you need to rectify pump issues is a 2mm allen key (assuming the pump is ok). Make sure you have it (2mm hex) in your spares bag before attempting this or a road trip.

The theory - back-flow (bypass) valve
The primary issue (I think) is the setting of the back flow valve (which is part of the pump). This valve takes excessive pressure from the pump (outlet) and diverts it to the inlet (to be re-pumped/think 'wastegate'). I am guessing here but I think this is so that 2x taps (hot/cold) can be run at once and both hold good pressure... so the pump cfm exceeds the flow from one tap. The problem is therefore if the pressure from the mains connection exceeds the pressure setting (and the setting of the negative head pressure) then (mains) water will flow back into the tank.

Also if this valve is set below the pressure value of negative head valve (the next 'in-line') the pump will always be on and merely be circulating water (or air) through itself.

The Theory - negative head (pressure) valve
The negative head valve tells the pump when to turn on. Once the appropriate pressure is reached it turns the pump off. When you turn a (say kitchen) tap on the pressure in the system drops (ahead of the valve) and the pump activates to boost the pressure.

The theory - interaction b/w the negative head and back-flow valves
Without getting too far out of my sphere of limited knowledge/experience (I haven't quite worked out how to calibrate the system from scratch) I can confirm they need to be adjusted wrt each other. If either of these are set incorrectly then you will get problems although I suggest most people will need to adjust the backflow valve.

The theory - Other NRV protection
On my 2016 20' expanda I see no other NRV's (non-return valve) other than contained in the pump assembly. The backflow (bypass) valve noted above should function as an NRV if adjusted correctly.

The adjustment (with 2mm hex/allen key)
The Shurflow manual dictates how to fix the problem/calibrate the system with a pressure meter which I don't have. My problem was with the tank filling and air (recirculating via the back-flow valve) in the system. This happened only occasionally when mains pressure exceeded the back-flow valve setting. I would start out by adjusting the back-flow valve clockwise (increasing the pressure setting) so the valve remains shut when the system is under mains pressure (this also increases the pressure the pump will return/divert some excess pressure from the outlet to the inlet and the pump will be more likely to temporarily stop/be intermittent). I would adjust half a turn (clockwise) and turn on tap (for a few seconds) and leave it for a while to see if the tanks fill and if so keep doing half a turn. (keep a record of how far you adjust otherwise you won't know where you are). This may lead to the pump starting and stopping because the back-flow valve is not recirculating excess pressure. Also may lead to hot/cold water cycling (shower getting hot and cold).

Negative head/Pressure switch adjustment. I wouldn't touch this in the first instance however.... Turning clockwise will result in a more sensitive switch (more likely to cycle). Turning counterclockwise makes the pump less likely to cycle.

I attach a photo of the pump and the adjustment (2mm hex) grub screws (directly below centre of text). Also the pdf of the manual with more info.

Again I am 'half-baked' with this information and have so far cured my (backflow/spitting) problem but need more adjustment to get the pump return (bypass) operating correctly with the pressure switch/valve. I would not make too many adjustments without keeping a record of them and their impact on your system. Make small adjustments over sufficient time (a day or so) to fully determine their impact.
 

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jazzeddie1234

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I have had issues with tanks filling back through the pump and very noisy operation so I dismantled it. The pump has an internal non return valve as well as the bypass valve and the pressure switch. In my case the nrv was sticking (no obvious reason as all looked new) so I added a seperate nrv just after the pump. I now have 3 nrvs in the system: in the pump line, in the feed to the hws, in the pressure reducing valve connected to the mains inlet.
My pump needed adjustment with the new nrv in place so this is what I did:
1 Wound the pressure adjuster out several turns and the bypass in several turns
2 turned on the pump and fully opened a tap with the mains water connected and turned the pressure adjuster in until the pump ran smoothly. There was a noticable change in pump noise. Then added 1 more turn. Remember to wait for the pump to prime!
3 left the pump running and 1/2 closed the tap. Adjusted the bypass valve out (several turns) until the pump stopped pulsing. I could hear the hiss of water in the bypass.
4 checked the pump stopped properly when the tap was closed. Disconnected the mains and checked again by opening and closing a tap.
5 in my case the pump would still pulse every few minutes even with the taps off so i turned the pressure adjuster out 1/2 a turn. I think I have it set correctly because the pump operates (when I first switch it on) for less than a second if the mains is on and taps closed. Opening a tap lets the pump run so it must be overcoming the mains (which is 350kpa max due to the prv) but not supercharging the system. The pump does not pulse on a partly opened tap but I found that the bypass it too difficult to set at a trickle.

In my case the pump is the quietest it has ever been so very happy.

Btw: make sure you have all the air out of your hws as air compresses and will mess with your tests.

On a seperate note you may have seen a schematic where there are only 2 nrv in the system (no nrv in the feed to the hot water tank). I don't like that because there is a risk of water backflowing out of the hws into the cold feed. Jayco plumbed mine with it in the hws.

And no I am not plumber, I just spent hours trying to figure out how to stop the pump from pulsing

Good luck with yours :)
 
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Lap Dog

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Cheers @Bluey. @jazzeddie1234 this is exactly this is the sort of response I was after - how to calibrate the system. If you read between the lines in my original post you will notice that I got a bit lost when trying to calibrate the system after I backed off both adjusters to 'prime' the system with mains water. I found myself making random adjustments but got somewhere near optimal eventually. Maybe I will follow your lead and end up adding an aftermarket NRV upstream of the pump if I get any further issues.

I was a little surprised you found an NRV in the pump. It is not found on the schematics in the manual and I only pulled down the main body (with childlike enthusiasm and wonder and with little idea what I was looking at) and didn't find one. In my original post I concluded the bypass valve acted as an NRV ... happy to be corrected.

Regarding the NRV on the hot water system. It appears (unconfirmed) I have one however it's plumbing is a little confusing for the layman/me. It has 3x inlets/outlets so is not inline. Picture attached (it has a blue cap on the top which I took off for the photo).

Thanks again @jazzeddie1234
 

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jazzeddie1234

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That photo is the water tempering valve, hot in one side, cold in the other, center is the mixed 50 degrees hot water output to sink and shower etc. Look for the cold feed into the hws and follow that back to the pump. In my case the hws nrv has an isolating tap and the only clue is the arrow engraved on the side.
The pump's nrv can be found under the pressure switch. Remove 3 screws and carefully remove switch body. Underneath is a spring and a valve. This is the nrv. It's F and G on your schematic. Frequently called a check valve....

Cheers
 
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Crusty181

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When the van was new (2014) the mains was back filling the tanks. The dealer nominated the water pump needing adj. I presuming from you guys they have tweaked the backflow?

Last year my pump was cycling intermittently, and often it would start pumping and not turning off at all. We started to use the pump switch to as the "tap". We free camp a lot so mains wasn't compounding the issues. It didn't happen all the time so I suspected it may have been a low voltage issue. I found a very basic online guide to adjusting the pump which blamed showers in general as the biggest cycling issue; ie get the shower right and all else will fall in line. The adjustment was basically turn the shower on full with a normal hot/cold mix and adjust the pressure switch until the cycling ceases and that was it. Worked for me, I haven't had any other issues since; no cycling and the pump turns off in around 1 or 2 secs.

Whats the reasoning behind you guys adjusting the pump pressure switch with the mains connected ?? Does that not throw everything out of whack again when you use the pump without the mains connected.

I found this reference for whats its worth

4008-pump-adjustment_thumb%25255B3%25255D.jpg
 
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jazzeddie1234

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My theory is that the pump pressure should exceed the mains pressure (which is limited by the prv) otherwise the pump would not operate properly with mains connected. I don't have a means to measure pressure so used the mains connected as a guide. When the pump stopped clicking and pulsing I assumed the pressure was about right. In my case the pump noise has dropped dramatically and shower pressure is just a little more than mains, not the 'empty your tank in 5 sec' pressure as before.
Did you use that guide to adjust?
 

Crusty181

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My theory is that the pump pressure should exceed the mains pressure (which is limited by the prv) otherwise the pump would not operate properly with mains connected. I don't have a means to measure pressure so used the mains connected as a guide. When the pump stopped clicking and pulsing I assumed the pressure was about right. In my case the pump noise has dropped dramatically and shower pressure is just a little more than mains, not the 'empty your tank in 5 sec' pressure as before.
Did you use that guide to adjust?
I haven't used that guide, my pump seems to be fine for now, but Ill keep that guide handy for "roadside adj" reference. I have a pressure gauge lying about, I suppose I could connect it to read line pressure and adj as per the pumps specs.

otherwise the pump would not operate properly with mains connected.
Why are you using and adjusting the pump when the mains is connected?
 

jazzeddie1234

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Don't as a rule but the toilet flush button operates the pump and while i didn't check, i didn't want it pulsing on flush.
 

Lap Dog

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Thanks @Crusty181 for the rough calibration guide ... seems a great place to start. I never run the pump and mains at the same time ... in fact I purge the mains pressure from the system before I turn on the pump. The first time I had a backfilling issue (tanks filling) I accidentally left on the pump with mains ... which led me to adopt this overly cautious and almost certainly unnecessary practice. I assumed at that time that the mains and pump pressures equalised causing the NRV to be open. Since @jazzeddie1234 confirmed the NRV has a spring I don't know what to think.

I still am perplexed by the failure of the pump NRV to do it's job.... it seems to be a common problem. The NRV is a simple design concept with little that could/should fail. There must be something else at play. I purged the air from my pump by backing off both the pressure and back flow adjusters and letting the mains pressure through and should not have been able to do this had the NRV been operating correctly.

Anyway my tank backfilling issue seems to be solved for now ... a few days back all seemed to be good and went off mains water and gave another test and the pump wasn't smooth so might give Crusty's callibration a go as a starter and use @jazzeddie1234's for finer adjustments. Seems like you need to give a change in calibration some time to take. At least I now know which adjuster does what.
 
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