Shurflo question

Having had continual airlocks with the submersible pump in my Bourton I decided to fit a 20psi Shurflo pump. Consulting many of the post on here it was a relatively easy fit and all seemed well. During my first trip away I found that a short flush of the loo or opening a tap for a short time caused the Shurflo to make a humming noise but not pump. This noise would go on continuously until a tap was opened fully then the Shurflo would pump properly but seemed louder than normal. If a tap is opened to wash or fill the sink for example the pump works fine with normal noise level. I think a small pressure drop (short flush) causes the pressure switch to trigger but the remaining pressure in the system prevents the pump from running (stalled). The pump is new but I wonder if it is faulty? The set up is not usable in this state and I’m planning to go back to the submersible if I can’t find a solution.

Regarding the submersible pump I found a post on here where someone found that by increasing the length of pipe the submersible pump is on so the pump rests on the bottom of the tank at 45 degrees eliminated the air locks. What’s the thoughts on this? is it worth dropping the tank to try this?

Hi R88
Sounds to me like the pump is "cycling", so the pressure switch adjustment screw in the base of the pump needs to be screwed in (maximum of 1.5 turns, according to Shurflo instructions).
If that doesn't cure it an accumulator may be needed.

When I helped to fit a Sureflow pump it was advised that an accumulator should be fitted with it. Other people have said it saves the pump tripping on for short use of the water like flushing.

Stalled might just be the word. Does this happen with the battery on charge? A steady electrical humming or buzzing noise would suggest that the motor is struggling to start the pump, which could indeed be a faulty pump but might possibly be due to insufficient volts at the pump.

Is there an external non-return valve in the system? If so where is it, before or after the pump?

As I have said elsewhere in my opinion a lot of the wiring in these vans is undersize, causing excessive voltage drop. Shurflos need a good jolt to start since the swash plates are under some degree of back pressure from the system, unlike the in-tank submersibles which are just a freely rotating centrifugal impeller. If the pressure doesn’t drop promptly as an outlet is opened then the motor might be constrained by the back pressure in the system. Measure the voltage at the pump as somebody else tries to flush the loo. If the voltage dives the pump is drawing power but cannot start.

Thank you all for the suggestions. To keep the installation simple and the space available in this version of Bourton, the pump was sited upright and basically replaced the whale pressure switch. The Shurflo pressure adjustment screw is not accessible with the pump in location and therefore I couldn’t easily make adjustment. The stalling issue is not mentioned in the reasons or troubleshooting sections of the manual for making adjustments so I didn’t try while I was away.
Last night I removed pump and decrease the adjustment screw in stages. After a few steps the stalling issue has been eliminated, so I can only conclude that as mentioned above back pressure was preventing the pump starting I guess the stalled motor would eventually have burnt out if left.
It would not be very easy to fit an accumulator without major plumbing changes.
I don’t think there is an external Nrv.
The main issue now is the vibrating noise of the swing wall makes as the system pressures back up.

The reason that I mentioned the NRV is that some installers, including myself, fitted an external NRV just downstream of the pump (on the outlet) to overcome the problem of tiny particles in the water fouling the built-in NRV and allowing back flow to the tank. If that (optional) NRV is installed upstream (before) the pump then the system pressure is lying against the swash plates. You wouldn’t think that this would cause a problem but going back some time (seventies) I recall a lot of problems with failed micro switches (the actual pressure switch) where the micro switch would fail “on” and the pump would run until it physically stalled and burnt out (or the fuse blew). Hence again some installers (including myself) also fitted an external pressure switch to improve reliability.

Personally I don’t think the NRV hypothesis is the problem, but it is a possibility if one has been fitted inadvertently, or remains 8n place, upstream of the pump.

The OP perhaps needs to address again the question of is this reported “hum” indeed continuous as he says, which would suggest a stalled motor, or intermittent in the sense of “on-off-on-off” which would be “cycling.”

I would still suspect voltage drop but it is easy to test this either by meter or by simply connecting the pump temporarily to the battery with some heavier cable.

Anyway, I now see that the OP has apparently cured the problem by reducing the cut-off pressure, which will effectively de-rate the pump and reduce the starting load on the pump motor, so all would seem well!

Thanks Caraman, I will try that, as you say the pump it’s self is not too bad.

I also have a Shurflo pump fitted to our Bourton, after the original pump failed.

The pump is fitted on large rubber mounts which cut down the noise. I also have some sound deadening material around it.

I haven't found the need for an accumulator, although I was prepared to fit one.

The pump runs smoothly, even if the taps are only partially opened. I do, however, have aerator/spray attachments (see photo) fitted to both taps, which restrict the flow. While they reduce the amount of water used by half, they still produce a strong spray, which can be directed around the sink and wash basin. With such a small water tank fitted to the later Bourtons, the water saving is a godsend. I have also reduced the water used in the shower by half, with an aerating shower head.

I have the same problem with my new Shurflo and whatever I've adjustments I've made to the pressure screw don't seem to solve this. So it looks like tge bext thing is to fit an accumulator. I was wondering what size folk suggest getting. Thanks

Caraman wrote:I have noticed with mine that if the slightest air is sucked into the pump, it makes more noise.  On mine I have to make sure the filter is seated properly and tight and its connections are similarly tight

Thanks for the reply.  I've checked all connections and none appear to be leaking. Could air still be getting in though? Also I didn't use a filter when I installed the pump yesterday as I didn't have one with me here in France. Thanks

Thanks @Carman. I guess I'll have to fit a filter to see if air is getting in. Not sure there's any other way. Is there a specific transparent filter you'd recommend.  Cheers

Ok found the filters online. I suppose the next question is if I  detect air getting in how do I fix this. Is it just a question of tightening all connections?

@Caraman thanks again for the latest. I fitted the pump yesterday but it the sputtering does seem to have got worse. It used jubilee clips over the connections to the bigger pipe and had to heat the original water pipe to push in the connecting barbs. So at the moment I'm not sure if air is getting in on the inlet. However over the years there has been issues with the hot water and definitely some air getting into the system there. But that's onbthe outlet side? Any ideas on how I could sort that? Would an accumulator be the best solution,?Cheers.

So attached is a photo of the pump installation. On the inlet side I had to insert one new connector between the new blue water pipe and the existing original water pipe. I've used jubilee clips at both ends of the blue water pipe. Not sure if the existing John Guest connector could have a leak? BTW the white masking tape is to hold the live connector in place as I'm using the old one and it was a bit loose.

So back home and I've had tme to check everything. The shower head connection was leaking a little and I tightened this. I also ran the system for a few minutes and all in all it seems to not be sputtering anymore. I'll keep an eye but hopefully this is sorted. I've also put a bit of packing around the pipes at the back of the swing wall as you suggested previously and this also helps. I also found that the sliding mirror doors on the cabinet above the basin rattled and a small bit of foam between these also helps deaden the sound. So thanks again for all the help.

Just one additional thought for future reference (but hopefully not!). It is worth checking that all the bolts around the periphery of the black pump body are reasonably and roughly equally tight. Have known air pulled in through there.