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Monday, June 6th 2016, 7:50am

Watts 800M4 backflow making scary noises -- “DUM DUM DUM DUM DUM DUM DUM”

At some point during every watering cycle, my backflow makes a series of rapid “DUM DUM
DUM DUM DUM DUM DUM” noises approximately 5-10 times. Apart from this,
everything else seems to be working fine.

So far I have not been able to replicate this problem, although I haven’t had a chance to
look at it too closely. In the past I have seen it happen and it’s definitely
the backflow. My hunch is that it is happening with the 1st or 2nd
zone. Last night I manually kicked on the 8th zone and didn’t hear
the sound.

I have a Watts 800M4 backflow. I replaced the bonnet, bonnet o-ring, and vent float last
night. But this did not fix the problem.

Any thoughts would be much appreciated. What’s causing the noise from the backflow?


Supreme Member

Posts: 5,331

Location: Metro NYC


Monday, June 6th 2016, 1:27pm

perhaps the noise source is something else and the PVB is serving as the loudspeaker - pin it down a bit better as to just when the problem occurs, like maybe when one particular zone opens


Supreme Member

Posts: 482

Location: Houston, Texas


Monday, June 6th 2016, 7:35pm

I think I have seen this before.

As you manually scroll through the timer zones, see which zones that the sounds become a factor. Like every time zone 3 comes on or every time zone 3 5 and 7 come on.

I think it will be the diaphragms in these trouble zones. If there is a master valve it could be the master valve diaphragm. But don't just replace all of your diaphragms, try to figure out which zones are having the issue. It will usually present it self as the timer switches from zone to zone.

That is what I have seen before.

It could be another issue.

Keep us posted. :thumbsup:
:thumbup: :thumbsup:
LI0006121, BPAT0011021, CI0009500


Tuesday, June 7th 2016, 9:01am

Ok, thank you very much for the feedback everyone. If it's not just a simple issue with replacing some parts in the backflow I think I need professional help with this one. I'll test it more tomorrow.

thanks again


Supreme Member

Posts: 482

Location: Houston, Texas


Tuesday, June 7th 2016, 9:54am

It may be a good idea to call in help.

But you need to get definitive information first, that will save you money on the repair.

Also, if you don't specifically know when this issue happens, then when the repair guy holds out his hand for money you will not be able to understand that the issue is fixed.

My 2 cents, spend about 20 minutes manually going through the zones at the controller to try to recreate the issue.
:thumbup: :thumbsup:
LI0006121, BPAT0011021, CI0009500


Supreme Member

Posts: 5,331

Location: Metro NYC


Tuesday, June 7th 2016, 12:05pm

the sight-unseen guess that could fit PVB noise is from a supply-side oscillation that happens when a zone opens and creates an extra-large demand for water

this scenario can require one valve opening while the previously selected zone valve has yet to close

one part of the evaluation would be to open a zone and see what happens, then to close the zone and wait for the water flow to cease, before moving on to the next zone

if there is a vast difference between one-at-a-time performance of manual operation and the two-at-a-time performance you can have during the overlap time when the next zone in a normal controller cycle is activated, then there are some remedies that might be simple to apply


Wednesday, June 8th 2016, 9:59pm

ugh this is frustrating. When I manually test it, I don't hear the DUM DUM DUM DUM noise. However, I can't get zones 2 & 4 to turn on. I try to manually turn them on several times and that doesn't work. I also set a new cycle for 2 minutes for each zone and they don't turn on either (all the other zones work but there is just two minutes of nothing for each zone 2 & 4). My control system (Irritrol RD-900) has been on the fritz for a little while now. I'm pretty sure these zones have been working all spring/summer, as the grass looks exactly the same in these zones as the others.

I guess the plan is to wait until the sprinklers go off in the middle of the night tonight, and if I hear the noise, I'll just get up and figure out what zone it is.

On a slightly separate topic, I think my Irritrol RD-900 is about 12-14 years old. If it does turn out that I need a new control system, should I just get the exact same one? Or is there something out there that is much better? thanks!



Posts: 2,397

Location: USA


Wednesday, June 8th 2016, 10:58pm

I've seen the RainDial cause major thumping noises. Three or four different controllers. It would send an on off on off on off signal opening and closing the solenoid reeking havoc.
The sprinklers still worked somehow. One lady had wicked hammering inside her house some 80 feet away from the valves.
Maybe the problem only occurs when the controller comes on via the program and not when you turn it on manually at the clock.
I've seen that RainDial do some crazy things. What year was it made? There's a date code inside the battery compartment.

It might not be the controller but I'd take a look.

To verify it was the controller i held a good solenoid to the terminals at the clock and you could clearly hear and see it clicking on and off.


Supreme Member

Posts: 482

Location: Houston, Texas


Thursday, June 9th 2016, 6:45pm

Good to know
I will start looking at that possibility next time I come across this issue.

I only get it about 1 time a year as a service call.
:thumbup: :thumbsup:
LI0006121, BPAT0011021, CI0009500


Tuesday, June 14th 2016, 9:13am

I figured out it's zone 5 causing the problem. But the thumping noise only occurs during the full cycle, not when I manually turn on zone 5.

Could the thumping noise be caused by the Irritrol RD-900? Or not likely?

Hoping to have my sprinkler repair come take a look later this week.


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