Hi all. Hope someone can help me. I have a alpha innotec heat pump with ground collector installed (german make). For the past 12 months i've been noticing a slow pressure drop in the ground collector system. Generally it drops 1bar in about 6 months. However, we've an unusually cold winter here in Ireland and I've seen the pressure drop 1 bar in 3 weeks! I have also noticed that when I refill and repressurise the ground collector the higher the pressure I fill to the quicker the pressure drop. This has me a worried. My main concern is that my collector manifold is in a manhole and is often underwater. Could this be causing the manifold to leak, dropping pressure as a result. Could the cold conditions have made this worse? Is a pressure drop over time a normal occurance or have I got a problem.

Sounds like you have a leak.  There would be some natural variation in the pressure... lower when it is cold, higher when it gets warmer, but a steady pressure loss sure sounds like a leak to me.

Ed

Higher temperature usually equates to higher pressure, but I suppose that depends on the materials involved (the pipe and the fluid will expand and contract at different rates).  In any case, there will be some normal pressure variation.  If pressure - always - drops, there is a leak.
Ed 

Thanks for confirming my fears. I think I am going to have to replace the manifolds in the manhole unless someone can give me another way to do this.

I think it wise to find a leak before replacing parts.

Yes but I have 100 meters of pipe buried 2 meter under ground in my garden, how would I possibly find a slow leak (probably no more than a drip) in that??

You may want to first try "Geo-Loop Conditioner" which can seal slow leaks in HDPE.

-Adam

Adam - Thanks, I was not aware such a product existed. I'll give that a go 1st. I still believe my manifold are a problem giving that there is some evident rusting on the valves due to it being submerged in water sometimes. I have found a supplier selling a thermoplastic manifold and he guaruntees it will work under water and even covered in ice. Thanks for the help everyone.

Can you hold off until drier weather allows more careful inspection of the manifold and leaks to be more evident?

I'd be a bit concerned that any additive promising to stop leaks might also coat heat exchange surfaces or foul pumps

Engineer - I actually did that exercise last summer (this leak has been going on a long time!) but I just could not make out anything. Surely this leak fix liquid would be harmless to pumps if it is specifically specified for geothermal systems?

Most pump companies do not recommend loop conditioner. Most hdpe pipe and fitting manufacturers say that that stuff is doesn't make any bond to the HDPE. I would definitely try and fix the leak.

I'm concerned that it would foul the rifling and convolutions within the heat exchanger.

Not much sticks to PE plastics - that's a good point as well

I was searching sites in the UK and Europe and no one has this fixaleak or Geo Loop Conditioner over here at all. Seems to be only in the US. Maybe I will go ahead and replace the manifolds 1st and see how that works out.

Is there a harmless dye (like food coloring) you can put in your system to determine if the manifolds are leaking? Seems like it would show up even if they are under water.