Pressurising ground loops

[pudding]

Hi,

 

I've had my GSHP for  4.5 years now. All running well, only niggle is i've had to have the pressure topped up twice in the ground loops outside in the field. We've got about 550m straight pipe outside so a fair amount. The first time the pressure was topped up was after less than 1 year. The last time it was topped up was nearly 2 years ago, and the pressure is very slowly falling, so the time between refills is getting longer and I'm hoping it was entrenched air in the pipes and a little expansion which is now coming to an end, only time will tell.

 

In the meantime, i'm reluctant to spend over £200 again for less than a half hr job, esp if the pressure needs topping up again, so would like to do this myself and with winter approaching i thought now is a good time to think about it before the system cuts out due low pressure in the middle of winter. Here's a couple of pics of the manifold chamber outside:

 

 

Any tips on the best way to re-pressurise the system. The installers used this - https://www.gogeothermal.co.uk/category/27/Filling-and-Flushing-Station which i think would be overkill for my situation and even doubt they would sell to me as a private individual.

 

I've seen this pump https://www.screwfix.com/p/rothenberger-rp30-pressure-testing-pump/83797 or even this https://www.amazon.co.uk/318927-Installation-Heating-Leakage-Pressure/dp/B00KBQPMII/ref=sr_1_6?ie=UTF8&qid=1536048793&sr=8-6&keywords=rothenberger+rp30 which look like they could do the job given the appropriate fittings/couplings?

 

I'm assuming this is fairly similar to pressurising an UFH system and doesn't need anything too fancy like the installers used? Will be looking at getting about 2bar, and the the pressure is measured on the GSHP unit itself so the accuracy of any pump i buy isn't essential.

 

Thanks.

 

 

[Jeremy Harris]

I reckon you could adapt a garden sprayer, as I did to fill and pressurise our UFH system and as is sold by one or two companies for filling and pressurising solar thermal systems.  All I did was buy a Screwfix garden sprayer (this one https://www.screwfix.com/p/sx-cs5-white-black-pressure-sprayer-5ltr/7490x I think), remove the outlet pipe and replace it with a bit of 8mm LDPE pipe, that I connected to a non-return valve and a fill loop flexi pipe, that screwed on to the filling point.

 

@jack took some photos of the fittings I used when I lent it to him:

 

 

 

 

 

The 8mm LDPE pipe fits the compression type fitting on the sprayer where the spray pipe normally goes perfectly, as that's also 8mm.  IIRC these things will pump to around 3 to 4 bar, which was fine for filling our UFH to 1.5 bar, as your system needs a higher pressure then such a bit of kit may or may not do the job, but I think it would be worth a go for the relatively low cost.  You do need to be careful when using it to not pump air in, although in my case there is an air bleed close to the fill point so any air could be bled out easily.

 

If you don't want to make one, some of the solar thermal system suppliers sell them.  At least one solar thermal supplier just modifies a hand sprayer as I did and sells it as a sort of kit of parts to fill up a system.

 

[Jeremy Harris]

Just found a better photo of the whole unit - looks like I used a 7 litre pressure sprayer rather than the one linked to earlier, although I doubt it makes any difference in practice:

 

 

The standard flexible fill loop hose just screws directly on to the non-return valve.

[pudding]

Execllent, thanks for the idea. Already got that exact green sprayer here, so will look into the parts needed to adapt it.

[Jeremy Harris]

The LDPE hose I used is like this stuff https://www.ebay.co.uk/itm/LDPE-plastic-hose-tube-x-30m-6mm-ID-8mm-OD-pipe-irrigation-pipe-tubing/112949756566?hash=item1a4c548296:g:jGYAAOSwYtla2KcE - I had some lying around from another job (probably still have a few metres of it somewhere if you get stuck and need some - I could easily drop a short length in the post).  The fill loop with non-return valve is one of these: https://www.screwfix.com/p/combi-straight-filling-loop/46605  fitted with one of these 8mm reducing sets: https://www.bes.co.uk/15-mm-x-8-mm-reducing-set that fits directly into the inlet side of the non-return valve.  I slipped a bit of thin wall 6mm brass tube inside the end of the LDPE pipe to prevent the olive from crushing it (B&Q sell 6mm thin wall brass tubing).  I permanently fitted the valve on the fill loop to our UFH filling point, but you could just discard it.  You may need an adapter to fit your fill valves - they look as if they may have threads that are larger than the 1/2" BSP thread that the fill loop connector has.

[pudding]

Perfect, shopping list formed methinks! Will hopefully get it put together next week and give it a crack.

[pudding]

So, picked up most plumbing bits from screwfix, and the rest of the bits arrived today (brass tube and pvc tube). So it's all a bit heath robinson and now looks like this:-

 

 

 

It now consists of 1" - 22mm adapter, 22-15mm internal reducer, non-return valve from the fill loop flexi-pipe, shut off valve, flexi pipe to pvc tube. Most important thing is it works! Had a bit of the glycol solution left over, diluted it a little, and have added 2 litres or so to the loops. Pressure gone from 0.7bar to 1.2bar. Result!!  Saved me over £200 on a callout.