Water pressure problem

[mark h]

After a shower a few weeks back, the pressure relief valve started pumping all of my fresh water into the canal. I have a shurflo 4901 - 4215 pump (30psi), a 5litre Zilmet accumulator, and a 3 bar prv.

I replaced the PRV for a similar 3 bar (with guage), and the problem still occurs, in that I switch the pump on, and if no taps are open, the PRV operates and start letting water go (the guage reads appx 3.2, at its peak). I have cleaned out the filter between the tank and pump - with no joy. I have tried adjusting the pump pressure screw (both clockwise and anti clockwise, and still the prv cuts in. I have tested the accumulator pressure (just before the PRV cuts in and its appx 20psi). I am have now got to the limit of my knowledge (not that it was high before), and am totally lost what to do next.....any ideas?

[OldGoat]

Subject to more experienced members here:-

 

a 3 bar PRV should not blow off until the pressure reaches 3 Bar - or 45psi in old money. So it's either faulty OR needs bedding down (on the few occasions that I've had to fit a new PRV, I have always rotated the cap a few times in order to 'bed it down' and clear any debris). It used to be good practice to preform this routine 'occasionally'.

 

Worth trying that?

 

Otherwise I've no further ideas (other than getting a new one - always nice to have a spare...)

[bizzard]

Sounds like the pumps pressure switch not working. You can remove pump and dismantle the switch. It might just be the little diaphram or hole clogged up with muck. Or renew the switch.

[MtB]

Initially I agree with Bizz. I think the fact that two different 3 bar PRVs are letting by indicates the pressure switch in your pump isn't switching OFF until well above 3 bar.

 

On his second point I disagree if you value you time. Just fit a new pump, they are cheap enough on ebay. You can waste HOURS on end faffing about trying to fix a pressure switch with no success in my experience

 

 

MtB

[ditchcrawler]

Initially I agree with Bizz. I think the fact that two different 3 bar PRVs are letting by indicates the pressure switch in your pump isn't switching OFF until well above 3 bar.

 

On his second point I disagree if you value you time. Just fit a new pump, they are cheap enough on ebay. You can waste HOURS on end faffing about trying to fix a pressure switch with no success in my experience

 

 

MtB

Agree

[bizzard]

The older Surflow Aquaking pumps with the square pressure switch attached on the back seem much more reliable than the later streamlined type with the switch built in flush.