Part Twenty Eight – 90% Finished, So Only Around 90% Left To Do…………

This twenty eighth entry was published originally by JSHarris on the 19th April 2014 and received 1,442 views on the closed forum

I know one shouldn’t ever start with an apology, really, but in this case it’s so long since my last update that I feel one is due. Several things conspired to delay this entry, ranging from getting pretty stressed out with the build a while ago, to smashing my camera on site and not being able to take photos. I’m pleased to say the stress levels have dropped, and as those who’ve popped in over the past few weeks will know, a fair bit of progress has been made.
I’ll start off with some photos to give an idea of the transformation that’s being going on. This is the view through the front door, with the hall decorated, the travertine flooring down, the oak doors and staircase in place, but without the glass balustrade panels fitted:

And this is the view looking the other way:

The underside of the staircase has a 6mm rebate routed in to the inner edges of the string, so that I can panel it with some 6mm oak veneered ply. The staircase manufacturer has thoughtfully provided some wedges, cut to the exact staircase angle, to glue and pin to the lower edge of the underside of the risers to support the centre of this panel

I spent a happy week fitting the kitchen units and plumbing in the integrated dishwasher, boiling water tap etc, plus doing the necessary wiring for the induction hob and cooker. We’re still waiting for the combination microwave to arrive, and the stone fitters have yet to fit the upstands and window cills, but this is how the kitchen looks at the moment:

Once we’d had most of the second fix electrics completed I arranged to get the PV system wired in and connected (on 20th March) so we just managed to get our system registered and beat the FIT tariff change at the beginning of April. As of yesterday afternoon when I left the site (just after 4 weeks after the system was commissioned) it had generated just over 620 kWh. It’s peaking at over 6 kW most days, and even on dull and cloudy days we seem to get around 1 kW or so from it much of the time. It looks as if our predicted generation for the year of around 7,000 kWh is about right. The inverter had to be mounted on the outside of the house, on the North wall, as it generates a fair bit of heat when working at full power, the last thing we want inside the house in mid-summer. Here’s a photo of the inverter, tucked out of the way around the back of the house:

I’ve also hooked up the ASHP, and fitted it under the inverter around the back of the house. It’s bolted down to some concrete blocks laid on their sides, which in turn are mortared to the retaining wall foundation slab:

The ASHP was dead easy to install, just a flow and return pipe (like a boiler) a power feed and a four way control cable. I’d already fitted ducts through the insulated wall for these connections, so ran the pipes/cables through then sealed up around them with squirty foam. The hardest part was fixing and insulating the large bore flexible flow and return pipes, as they are tucked away at the back of the unit and tricky to get at.

When I came to fit the buffer tank I discovered that it wasn’t a direct one as ordered, which caused a bit of head scratching at first. It seems that the manufacturer had accidentally fitted a 7kW coil in the buffer, making it an indirect one. After a bit of discussion with the tank supplier, and a few calculations, I decided that an indirect buffer was actually an advantage, as it allows me to have a very low volume primary circuit, which in turn means a massive saving in antifreeze cost (well over a £350 saving). In terms of extra complexity, it’s meant fitting an 8 litre pressure vessel and filling loop up in the services area, plus an extra bottle vent, but it does now mean that the main thermal store, buffer tank and UFH circuit can be filled with ordinary water plus inhibitor.

I’ve got all the buffer tank plumbing completed and have started plumbing in the thermal store (which should be dead easy, just a cold and hot water connection, plus the two 28mm thermo syphon pipes from the buffer and an overflow. I’ve run a length of 32mm waste pipe down from the first floor services area, behind the buffer tank and then along the wall to a trap, then the washing machine drain another trap and the connection to the main soil pipe stack. This waste pipe will take the overflow from the thermal store header tank and the two condensate drains from the MVHR unit, once I’ve figured out the easiest way to connect three 20mm pipes to a vertical length of 32mm pipe.

One small issue I’ve had is with sediment in the borehole. This was, to some extent, to be expected, as the upper layers the drillers went through were fine grained gault clay/mudstone, and they were wet drilling, so were pumping a lot of the black muck back down the hole to clear the debris out. The water runs crystal clear if left to run for a few hours, but when turned off and then on again it is sometimes a bit murky for a few minutes, before it runs clear again. I knew I’d need some sort of filtration system, but to work out which would be best I needed a water analysis. The local authority are obliged to offer a water analysis service for a fixed price of £25 (the rate’s set by central government), so I emailed them and rang them to find out how to get a sample to them for testing. This was the first time I’ve encountered the sort of bureaucracy that local government is infamous for. It turns out that they will test the water for £25, but won’t accept a sample that’s given to them, they insist on coming out and taking the sample themselves, for a fee of £100 on top of the analysis fee. The (rather unhelpful) chap in the Environmental Protection team told me that this was because the water analysis cost the council around £70, so if they didn’t charge the sampling fee they would lose money on every test. Clearly what they were doing was circumventing the governments intention to make safety testing private water supplies affordable, by setting the maximum fee at £25. In reality they were charging the £70 analysis cost, plus another £55 to call out and take a 2 1/2 litre sample of water. Not only that, but they insisted that they could only take a sample from either a kitchen tap or from a special sampling tap that was installed within a covered area. As I only have a standpipe in the garden this would have meant additional expense in sorting out something that met their requirements.

Luckily there’s a place just up the road from me that offers very sophisticated analysis capability if you ask the right person, so I took a sample, gave it to this “right person” and within 24 hours had all I needed to know to choose the right sort of filtration system. Our water is fairly alkaline (pH of 7.6) with a fairly high total hardness of around 260. It also has a fair bit of iron in it (0.22 ppm) and a tiny trace of hydrogen sulphide (0.2 ppm, which is way below the harmful threshold of around 5 to 10 ppm). The latter can be smelt when the water first runs from the tap, but isn’t at significant levels in terms of health risk. The iron level is on the high side, though, the recommendation is that iron in water shouldn’t really be above about 0.05 ppm and it would be a good idea (just for the sake of taste) to get the level of hydrogen sulphide below the human smell detection threshold of around 0.005 ppm.

Getting rid of this low level of iron and hydrogen sulphide is very easy, and can be combined with a filter to remove the fine sediment. Getting both the iron and hydrogen sulphide out relies on oxygenating the water, then passing it through a filter bed of manganese dioxide, with sand and gravel at the bottom. This works catalytically to remove both compounds, with the resulting sediment build up in the filter being removed by backwashing it to the drain every couple of days. All this happens automatically, with the filter media being held within a tall pressure vessel (rather like those water softeners use), fitted with an electronic control head and timer that periodically backwashes and regenerates the filter (by allowing the filter vessel to fill with air) at a set time (by default it does this at 3 am every other day). I’ve fitted this in the lean-to water treatment plant shed I built on to the back of the house, so we shouldn’t be aware of it flushing . Luckily we’d already run a length of perforated land drain pipe from the big soakaway under the drive along the back of the house (to take the run off that tended to collect on the retaining wall slab foundation) and the end of this was just below the water treatment shed. All I needed to do was push a long length of 25mm MDPE pipe down inside it and connect this up to the backwash drain outlet on the filter (the filter backwashes under pressure, so water flows out of this pipe under the pump pressure). I still have a bit more plumbing to do with the filter, but have got most of the connections made.

Getting water into the house will be a big step, as I can both start checking all my second fix plumbing for leaks and can get the downstairs WC working, which will save the cost of the portaloo hire. Once that’s gone (and the skip’s gone) I can take the Heras fencing down. By pure luck another self-builder a mile or so up the road wants to buy all my Heras fencing (as they are hiring at the moment, and realising how hire costs add up), so the timing couldn’t really be better. I’m looking forward to getting the fencing down and the skip and portaloo out of the way, as it makes the place look so untidy.

We’ve had a fair few visitors since the last entry I made here, including two visitors from the local authority, the Sustainable Energy Across the Common Space lady (see here: and the Energy Policy Officer for Wiltshire Council (who is also an enthusiastic AECB member). As a consequence our home is now part of an initiative to raise awareness of energy conservation measures in the home in this area, the South Wiltshire Green Doors programme. We’ll be open to show people around over the weekend of the 17th and 18th May, but visitors have to book through the Green Doors programme, here:

I’ll try and make updates to this blog a bit more regularly from now on…………………


ProDave 19 Apr 2014 08:22 PM:

I was wondering how the “black sludge” episode with the water was doing. Did fitting a timer work to purge the remaining sediment out and does it now run visibly clear?


 jsharris 19 Apr 2014 09:02 PM:

It’s a bit variable, Dave. Sometimes it runs clear within a minute or two of turning on, sometimes it takes two or three minutes or more before it runs clear. It pretty much always runs clear within 5 minutes, so I’m far from sure quite what’s going on.

I know that the borehole is down into a major aquifer, as even pumping at 1200 to 1500 litres per hour doesn’t drop the level at all. It may be that there is enough “cross flow” down in the bore to disturb the sediment, and may be this varies a bit from day to day. The general consensus from those I’ve spoken to is to just filter it out and backwash it to a drain every few days.

As I need to treat the iron in the water anyway, and as this treatment system needs backwashing every couple of days to regenerate the media, I’m just going to go with this as the main filter. I have plumbed in a Cintropur centrifugal filter, with a 25 micron screen before the main manganese dioxide/sand/gravel flter, as a way of collecting some of the sediment in a clear filter bowl to keep an eye out for any changes. This Cintropur filter has a drain port at the base and I’m thinking of fitting a solenoid valve to this, so that I can get it to blow out any muck for a couple of seconds whenever the pump turns on.

I have a feeling that I may have to just live with the water being a bit cloudy as it comes in, and let the filters sort it out. This is pretty much what the water companies do in many areas, anyway.


 Nickfromwales 20 Apr 2014 08:47 AM :

Hi Jeremy.

The house is looking great. The travertine is really nice, I’ve just done a hotel entrance lobby with the commercial grade honed and polished stuff with mosaic ‘doormats’ outside each door and by the entrance door. Looks stunning when the light hits it the right way. Don’t forget the impregnator sealer!

Is the inverter IP rated or is it going to be protected from the elements by a cover / other ?

The overflow pipe from the store goes to a trap, you say. Is it by luck or engineering that you have the two condensate overflows going into the same 32mm pipe? The reason I ask is I’ve seen plenty of overflow pipes which go to a trap before terminating to a soil / stench pipe. The problem is that there is no regular / occasional water flow through the pipes to replenish the body of water in the trap (which eventually evaporates and leaves the trap empty) so the stink from the soil pipe is free to come back through the empty trap and cause nuisance smells / draught etc.

Do the condensate outlets discharge water periodically throughout the year? I imagine you’ve engineered it but curiosity has the better of me!

Regards, nick.


 jsharris 20 Apr 2014 09:30 AM :

Thanks Nick. The travertine does look good, but I was a bit annoyed at the way the estimating guides for calculating the amount of adhesive, grout and sealer worked. We ended up with 7off 20kg bags of adhesive, 4 off 10kg bags of ivory grout and around 6 litres of (very expensive) Lithofin sealer left over. We sealed the travertine after fixing it down, but before grouting it, then sealed it again after grouting. I’ve got enough left over sealer to do the whole floor another couple of dozen times, I think!

The inverter is IP65 rated, so OK for outdoor mounting (it’s specified as an outdoor model). Another advantage of having it outdoors (apart from keeping it cool) is that it makes a definite buzzing noise when running near full power. Not enough to be a nuisance outside, but I think it would be audible inside the house and might be a nuisance.

It’s engineered to have two traps in series, Nick, as I strongly suspect that the tank overflow/MVHR condensate drain trap will be dry from time to time in the summer. The 32mm pipe runs down from the service area (where the three drain outlets need to be hooked up to it somehow) to the first trap, and then along the wall under the work surface in the utility room, where it connects to a 40mm waste and trap for the washing machine. This 40mm waste then runs across to the main soil stack in the downstairs WC. The idea was to avoid having holes through the external walls as far as possible.


 coopers 23 Apr 2014 08:04 AM :

Nearly there Jeremy. Any more pictures of inside and patio doors etc? Is the window colour silver or grey on the MJ chart?


 jsharris 23 Apr 2014 05:22 PM:

Hi Suzanne,

I’ve taken some more pictures for the next blog entry, but they are really showing some of the technical stuff. The windows and doors are dark grey, RAL 7015, outside, plain lacquered pine inside.

There’s still a great deal to do, and it’s all down to me, so is going slowly! I’m hoping to get the water supply in and working this week, and then get the downstairs WC in and working next week, along with commissioning the MVHR and perhaps the ASHP. After that I still have to fit out both bathrooms, lay all the bamboo flooring, fit all the oak skirting and architrave and fit out the utility room. I can spend a whole day working non-stop at the moment and nothing much looks any different afterwards!



 coopers 23 Apr 2014 07:59 PM:

It will be fabulous! What made you choose the bamboo flooring? We’ve no idea what we will have yet.


 jsharris 23 Apr 2014 09:06 PM:

I do hope it turns out OK………..

The choice of bamboo was primarily because it is very, very hard. This means it’s harder to dent or mark (although it can still be scratched) than wooden floors. It’s also fairly thermally conductive, and when glued down (rather than laid as a floating floor) it works well with UFH. Finally it’s relatively inexpensive (around £20/sq m) and has great eco credentials (as it’s grass, and grows very quickly, locking up a fair bit of CO2).


 couplands 28 Apr 2014 01:38 PM:

Hi Jeremy, I note you say glue the bamboo flooring down. Is that because there is little need for expansion in your house due to stable temps..?

I have generally laid floors loose/floating in the past. Not that I’ve laid a lot of floors..:-)


 jsharris 28 Apr 2014 03:10 PM:

Apparently gluing the floor down still allows expansion, as the adhesive is a modified silicone, so remains flexible. You still need to leave 10mm expansion gaps around the outside when using the adhesive, just as you do when laying a floating floor.

My reason for gluing it down (at least on the ground floor) is because it reduces the thermal resistance, so the the UFH should work a little better. It also makes the floor feel more solid, I’ve been told, and with plain T&G flooring it avoids the need to glue the tongues with a bit of PVA when laying. The downside is that the adhesive is expensive. I’ve gone for Sikabond T54, which is specifically designed to allow floor natural movement.


 ProDave 03 May 2014 06:37 PM:

I’m after more details of your ASHP. I’m leaning more towards that and abandoning my plan to use ground source.

 So yours is “monoblock” so it’s all in one. So it just sits outside, extracts heat from the air, and sends that to the house via flow and return hot water (circulating antifreeze) is that right?

 How noisy is it? If I choose that it would go under the car port the far side of the garage to keep it as far as possible away from the house as we don’t want to be able to hear it. Alternatively can it be wall hung on the garage gable end above the car port (if there’s any technical reason why it might not work well under the car port)

 This would mean fairly long flow and return pipes. I guess that just means a bit more antifreeze needed and not other issues as long as they are well lagged?


 jsharris 03 May 2014 07:42 PM:

Yes, a monoblock is pretty much the same as a boiler, just a water flow and return plus power and control wiring. The water needs antifreeze, solely for the case where the temperature drops below freezing and there’s a power cut, as when there’s power the unit has freeze protection (by just running for a short time at very low speed to keep itself warm).

In the end I bought a new Glowworm 7kW Envirosorb2, for £1700 inc VAT and delivery. It came with an internal programmer/control box, that’s connected by a four core low voltage cable. It’s a massive overkill for our needs, but there was nothing that came close for an equivalent price.

It’s very quiet, unless being asked to deliver high temperatures, when it does hum a bit. I accidentally set it to deliver 55 deg C flow temperature when the outside temperature was around 8 deg C, and it was noticeably noisy outside, but I couldn’t hear it at all inside, even right by the wall where it’s mounted. It’s about a metre from our back door and maybe 300mm from the rear wall, mounted on blocks mortared down to the retaining wall foundation. This meant very short connecting pipes, and as this is at the back of the house it’s well away from habitable rooms (the living room is the other end of the house at the front). There’s no need to run it at night, as the house will maintain night time temperatures from the residual heat in the slab and the heat in the buffer tank.

I’d not wall hang it, as I suspect it might transmit vibration into the structure. Better to bolt it down to solid concrete and isolate it with large bore flexible hoses. I very much doubt if you would be able to detect it running from inside the house, even if it was mounted just the other side of an external wall. If you really do need to position it so there are long pipe runs, then you could look at running them in very well insulated ducts under the slab, as that might reduce the losses in very cold weather. I’d also think twice about fitting it under a car port, as that might tend to amplify any noise. I’m sure ours sounds noisier than it really is because it’s in the deep corridor at the back of our house, between the house and the retaining wall. This means that the retaining wall tends to reflect any noise back to the house, yet still I can’t hear it inside when it’s running at 40 deg C flow temp.

 The secret to keeping the noise down seems to be the inverter technology. Ours will run with the fan barely ticking over, or even stopped, when only asked to deliver a few hundred watts. AFAICS, it’s a bit like a very wide range modulating boiler, and is capable of running from a few hundred watts output up to about 8kW output when the conditions are right. It heats a 70 litre buffer tank from cold to 40 deg C in around 20 minutes, and that’s then enough to heat our house to 20 deg C when it’s 10 deg C outside for a several hours. When working at this flow temperature the fan on the unit is barely spinning, and it seems that the fan is the major noise source.

If worried about noise then I’d be inclined to look at over-sizing the unit. You might lose out a little bit on efficiency, but gain by having the fan only run very slowly most of the time.


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