Pressure Test Length / Pressure Dropping

[jamesmonk83]

Hi All,

 

My wife and I our renovating our first house together and have become a little stuck installing our wet underfloor heating system. Before we end up phoning around local plumbers I thought I'd post on here to see if anyone has any bright ideas....

 

We've laid the pipes (2 zones), attached the manifold to the wall with the ball and drain/fill valves and run water around the system from the mains (one circuit at a time) as per the manufacturers instructions. We've carefully gone around checking the pipes and there are no signs of any leaks so we started pressure testing the system. At first there were obvious leaks around all the valves so we re-fitted them and tightened them up which has stopped that however the pressure isn't holding for very long. According to the manufacturers instructions the system needs to be at 6 bar for 2 hours. Our system does appear to hold the pressure for this long however whenever we've left it overnight it always drops by around 1.5 bar.  We're not sure whether this is normal or something to worry about? We've doubled checked all the connections on the manifold and there are definitely no signs of any water/leaks and the pipes aren't leaking so we're a bit mystified as to the pressure would drop like this.

Any help/advice would be greatly appreciated.

James

[Tin Soldier]

Hi,

 

I assume its just cold water that you are putting in the loops at start of the test?

[Jeremy Harris]

A small pressure drop when testing overnight, as things cool down, is normal.  Water is virtually incompressible, so with the system full of water, with no expansion space, then the pressure will go up and down a great deal with temperature.  Even a tiny amount of expansion as the water warms up will increase the pressure a fair bit, and the same applies as the water cools down and the volume of water decreases very slightly.

[Mr Punter]

Pump it back up to 6 bar in the morning, then check again in the evening. If it still falls, check your test equipment is not leaking.

[Vijay]

if you still think there is a leak, maybe get some UV dye and a UV torch, that might help show up an leaks?