Setting a Pressure Reducer Valve on a maxiflo-fed power shower

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Hello forum,

Background to problem:
I used to have a gravity fed hot water tank, and hence had an Aqualisa power shower. However about 5 years ago, I had the regular hot water tank changed for a maxiflo system. To avoid the power shower needing to be replaced (due to the increased water pressure), a plumber fitted 2x Pressure Reducer Valves on the supply into the power shower, and this has always worked fine for 5 years.

Problem:
Last week, the Aqualisa power shower died (it was 10 years old and not uncommon at that age). I'm fairly handy and bought and fitted a new one myself - which was a straight swap. However, I had to play around with the screws on the pressure reducer valves to get the water through, as it was not flowing for some reason (I'm unsure if this was a safety feature of the valves, or whether they've corroded inside and they were stuck ?), and meant the shower was just running dry - which I immediately stopped. Adjusting and opening the valves a little did work as it suddenly allowed water through to the shower unit. I thought that was all fine then and the shower remained working for the 10mins I waited there with it.

However, it only worked for 2 days, and now the water isn't coming through the valves again. I'm guessing I either reduced the pressure too much (to be fair I did go on the side of caution with the pressure I set it at), or the valves are stuck/corroded.

Obviously I will get a plumber out if need be, but I like to learn and understand these things and do what I can myself.

Assuming it is just that I reduced the allowable pressure too much, am I right that to correctly setup the pressure on the valves I should do as follows.

The power shower requires a working pressure of between 0.1 and 1.0 bar.
1) Ensure the shower is not running (i.e to set static pressure).
2) Adjust the screw on the pressure reducer valve to 1.0 bar or just above (the max inlet pressure for this shower). This will hopefully allow water to flow into the power shower chamber - just as it did the other day.
3) Run the shower for a few mins, which will cause the pressure to drop (the gauge will now be showing flow pressure).
4) Monitor the flow pressure, and if goes near 0 then slightly increase the pressure, keeping it below 1.0 bar.
5) Turn off shower and check the static pressure doesn't exceed 1.0 bar (or thereabouts)
6) Ideally I'm guessing I'd have a flow and static pressure of both between 0.1 and 1.0 bar ?

Or am I missing something ? Any (friendly) advice would be appreciated.

I've attached photos of the setup (ignore the pressure values shown as the photos may or may not have been taken when it was working fine)
Many thanks in advance
 

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You need a to have a flow through the PRV however small so open valves on either side of the PRV and adjust the setting screw clockwise to increase the pressure, keep adjusting until normal flow established. Why do you need two PRVs.
 
You need a to have a flow through the PRV however small so open valves on either side of the PRV and adjust the setting screw clockwise to increase the pressure, keep adjusting until normal flow established. Why do you need two PRVs.
Thankyou. Given the max pressure of the shower is 1.0 bar, should I try and set the PRV pressure at 1.0 bar (or say 0.7ish to be safe) with flow or static ?

I'm unsure why there are 2x PRVs. Maybe precautionary incase the cold supply ever went too high - I don't know. The guy fitted them and the maxflo had done quite a lot of these and an established plumber. Unfortunately he had health issues and recently retired, so I don't feel I can ask him for advice.
 
if it's showing zero pressure now, then slowly turn the adjustment screw clockwise, shower off, until you get say 0.5bar, start the shower, watch the pressure and turn the adjustment screw to give a max of say 0.5/0.7 bar. I think these showers are designed to be gravity fed from a cold water cistern, I know connecting a pumped Triton to the mains invalidates the warranty but I have installed a few for relations that way with no problems, so maybe max as stated above.
 
if it's showing zero pressure now, then slowly turn the adjustment screw clockwise, shower off, until you get say 0.5bar, start the shower, watch the pressure and turn the adjustment screw to give a max of say 0.5/0.7 bar. I think these showers are designed to be gravity fed from a cold water cistern, I know connecting a pumped Triton to the mains invalidates the warranty but I have installed a few for relations that way with no problems, so maybe max as stated above.
Thankyou. This is what I thought, but I'm no plumber - it just seemed the logical thing. Good to have a second (experienced!) opinion to give me reassurance.
 

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