Pump and hose vibrating. Can't find problem.

Ralph Q

New member
Yesterday I started up my washer, for my first driveway, and I noticed that the hose was vibrating slightly. I thought it was air in the hose. It stopped after a while and then came back. I noticed it at the next two houses. It sort of felt like the pump wasn't getting enough water.
So today I took all my plumbing apart and retaped and tightened everything up. It didn't help. It still feels like the pump is cavitating. Just not as bad as if it really was being starved. I know there is no air leak and my tank was full. So I'm stumped. Can anyone point me in the right direction in diagnosing this problem. I did run out of water and might have had the pump running out of water for like 30 seconds the other day, would that damage the pump?

Could this be pump damage or trash in the valves or something? What are the symptoms of pump damage due to cavitation? I have to work tomorrow and I am afraid I'm going to blow the pump.

The pulsating/vibrating is worse when there is a low pressure nozzle on or there is no tip one the wand.


New member
mine does that every once and a while, havent figured it out yet either, checked and rechecked all fittings, tank is full of water, checked pump seals and and sign of debri, all is good. Its not bad, just slight vibration like you said. Pump has maybe 500 hrs on it, dont know how many hours I should expect out of it.

Ralph Q

New member
Water filter(s) ok?

Filters are all cleaned. I've been using this set up for 8 months with no problems. I'm thinking there is debris stuck in one of the valves. Hopefully it's not pump damage. I just changed the unloader. Could that cause vibrating/pulsating?


New member
Do you have a way to pressure feed the supply to the pump? If you noticed it after you ran it out of water its possible there is an air lock / air bubbles somewhere in the pump or unloader that are unable to purge out for some reason.

Ralph Q

New member
Looks like I'll be busy, thanks for the suggestions.
I just changed the gun too. It was sticking for a few minutes.
The unloader has been on for a week. Many suspects. Going to try force feeding. If that clears it up, it's time for new plumbing!


New member
Just take the caps off the head and look at the valves. Hopefully it's just the o-ring under one or more valves, it usually is.

Sirocco Jerry

Active member
For the NEW GUYS..
NEVER Tear-into a pump without Checking ALL the EASYest stuff FIRST !!
Removing valve-caps your first time can be a real test of composure..
Use a PERFECT-fitting socket or box-end-wrench or you could easily strip the "brass hex"
from the caps you were planning to use to remove them.

And IF you go there.. do not put the valves back in until you check seals, and seats. ..meticulously.

Also clean ALL the thread sealant off the threads of the caps,
..and try to find some "Anti-Seize Compound" so they are more easily serviceable next time.

All that said.. you probably damaged seals running without water.. the ONLY question, is how badly.
..but also make sure there is NO Thermal Relief valve there.. they don't like suction-feeding from a tank, at all.
..They suck air, cause cavitation, and destroy seals.

Sirocco Jerry

Active member
Ralph and Connor..
If you don't find your pump problems with my previous post,
call me.. I'm a relentless troubleshooter. For over 40 years.