Then the pit was refilled with mains water, plus a few buckets of stream water, cos I like the idea that the stream water brings something different to the party.
The Torbeck valve works well and if I dip a couple of buckets out, the valve dutifully tops the heatstore up.
( I was worried that the Torbek float had to fully drop to trigger a top up )
Not much chance of the header tank stealing much heat, as the feed pipe is a foot long piece of 15mm speedfit and any flow from the heatstore to the header tank due to expansion of the stored water as it heats up, will be pretty limited. The overflow level is set 50mm above the top up level, so hopefully, with max expansion raising the water level in the store by 35mm, we will not overflow unless there is a problem with the heat exchangers or the torbeck valve.
Before winter I will apply expanding foam to encapsulate the header tank as much as possible and will probably stuff some rockwool up the overflow pipe to stop cold air getting into the header tank from outside.
Then on to the next challenge -
The lid of the store consists of a slab of 4" thick PU foam sculpted to fit the opening and shaped 'spillback' areas that cover the pipework.
Now this lid had become so heavy, it was sagging under its own weight !
Yup, it was fully saturated with water.
I thought that standing it on its end and leaving it to bask in warm sunshine for a few days would drain it dry but amazingly, it fully retains all its water and pressing a thumb into an undisturbed bit of silver covering, produces drops of water.
This means that any cellotex that gets wet, WILL STAY WET !!!! They don't tell you that do they.
Leak in the UFH ? yeah no worries mate ...........
Roof leak into that super insulated ceiling ? no worries, the insulation should stop the water getting into the room below for longer than you think .......
Sooooo ...
I made another lid.
Much measuring and walking between pit and workshop to cut some more and eventually the lid sat as it should.
Now to make up any gap between the underside of the lid and the ledge it sits on, I had already developed a trick with expanding foam laid onto a thin layer of plastic sheeting lid on top then weigh it down while it expands and sets.
Trouble is, expanding foam doesn't care how much weight you put on the lid, as it either lifts it as it expands, or it continues to expand once the lid is removed and the plastic sheet removed from the foam, allowing a bit more air and moisture to encourage further expansion and setting. Doh !
So I used the belt sander to work it back, using the general shape of the foam as a clue, with several more wanders between workshop and pit to check the fit.
Got a good fit and in order to stop the new lid from turning into a water filled monster , I decided to give it a coat of vinylester resin as that helpful techie made sure I bought 'enough' resin to do the job.
So why did the vinylester resin dissolve the expanding (PU) foam a bit but not the cellotex (PU) foam
And why did the whole lid curve upwards by a couple of inches leaving only the four corners touching
Bl00dy Chemists, they should stay out of plumbing I reckon
So I belt sanded the roughcast finish and re coated it, chainsawed slots from the top nearly full depth, fitted the lid to the pit, weighted it down, and foam filled the slots. Next day I trimmed the foam and vinylester resin coated the top.
Its not as good a fit as it was before I resin coated it though, so I stuffed a strip of expansion joint foam around the edge
