Passive house plumbing first fix - any tips

[markharro]

Just about to engage a plumber for this. He is going to use Hep2o which seems well regarded but other than that are there any pointers eg recommended bore of pipe? Do you routinely insulate hot and cold feeds? I think there is also a choice between radial and standard but I don't really understand the tech pros and cons?

 

Thanks

[PNAmble]

We are a few months from this stage but had all the M&E plans done.  We are going for a few radiators not UFH
 

you need to insulate cold otherwise you’ll get condensation on the pipes and you need to insulate hot plus heating otherwise you’ll get unwanted heating eg you don’t want extra heating in summer just because you are having a shower.  

[JohnMo]

I put in manifolds for hot and cold, lets you isolate a single room, without isolating everything. Good at the end of the build for doing rooms and bringing them online with others isolated. You can also run 15mm from manifold to the room. Insulation, I did insulate or run within insulation for the most part.

 

Do you have long runs? if so consider hot water circulation, if you go this route, hot water pipes all need good insulation.

[Iceverge]

Here's what I did.

 

25mm MDPE to the stopcock

22mm Hep to the control block and teed out to a cold water manifold. Hep push fit manifold. 

 

15mm for all cold requirements in a radial fashion. Pipe is cheap, joints are dear. 

 

22mm to a shutoff valve (to isolate the cold side if needed) and then 22mm UVC and then a very short run of 22mm to a hot water manifold that is vertically above the UVC allowing it to preheat via convention. 

 

10mm Hep to the basins and the kitchen tap as it's too far away. 

 

15mm to everything else. 

 

No joints in the pipes other than at the start and the end. 

 

I wish we had put a wetroom style floor drain in every room with a pipe joint in it. It would have ment that had we any serious leak the house wouldn't flood. 

 

 

 

[nod]

I’ve never seen internal pipes insulated on a new build home 

But there’s nothing to stop you 

 

[Huckleberrys]

1 hour ago, nod said:

I’ve never seen internal pipes insulated on a new build home 

But there’s nothing to stop you 

 

You can't have worked with many decent plumbers then! I always insulate the lot, no point wasting energy putting heat where it shouldn't be!

[nod]

2 hours ago, Huckleberrys said:

You can't have worked with many decent plumbers then! I always insulate the lot, no point wasting energy putting heat where it shouldn't be!

Probably more than you e had hot dinners 

[Gone West]

14 hours ago, nod said:

I’ve never seen internal pipes insulated on a new build home 

How many Passivhaus have you worked on? In the PHPP it requires the insulation levels for hot water pipes. The last thing you want in a PH is heat being introduced into areas where it's not wanted especially in the summer.

[ADLIan]

Insulation of pipe work is in building regs too, for the same reason

[markharro]

On 03/08/2023 at 22:22, JohnMo said:

I put in manifolds for hot and cold, lets you isolate a single room, without isolating everything. Good at the end of the build for doing rooms and bringing them online with others isolated. You can also run 15mm from manifold to the room. Insulation, I did insulate or run within insulation for the most part.

 

Do you have long runs? if so consider hot water circulation, if you go this route, hot water pipes all need good insulation.

Thanks @JohnMo I have had a couple of quotes from plumbers so far but no detail at all on how they propose to run the circuits. With you manifold solution does this add any complexity/cost other than than cost of the manifolds which I assume is not much? We have 2 showerrooms and a bathroom and planning only to fit out 1 of the showerrooms initially so this might be a good solution to that.

What is the relevance of running 15mm pipes?

 

Long runs - our utility room where the water comes into the house is pretty central - that said its about 12m as the crow files to our kitchen sink/dishwater - and quite a bit longer with all the pipe turns etc.

There are no other really long runs however. Can you explain what "hot water circulation" is?

 

On 03/08/2023 at 22:42, Iceverge said:

25mm MDPE to the stopcock

22mm Hep to the control block and teed out to a cold water manifold. Hep push fit manifold. 

 

15mm for all cold requirements in a radial fashion. Pipe is cheap, joints are dear. 

 

22mm to a shutoff valve (to isolate the cold side if needed) and then 22mm UVC and then a very short run of 22mm to a hot water manifold that is vertically above the UVC allowing it to preheat via convention. 

 

10mm Hep to the basins and the kitchen tap as it's too far away. 

 

15mm to everything else. 

 thanks @Iceverge can you help me deconstruct this....

 

the MDPE brings the water into the house to the main stopcock?

whats a "control block"?

"radial" - does that mean separate pipes to each location needing a cold supply? How does a "standard" circuit compare - does that have one main pipe in a circuit with Ts off to each room?

"UVC" - is that the hot water tank?

 

So 10mm pipe only for hot water supplied to far off locations - is the logic that this gets the water there fast and minimises wasted heat loss from a smaller volume in the pipe? 

 

So 15mm would be the norm for shorter hot water feeds? Is that enough throughput for showers?

 

thanks 

 

[JohnMo]

10 minutes ago, markharro said:

With you manifold solution does this add any complexity/cost other than than cost of the manifolds which I assume is not much?

It all becomes very simple, no hidden joints, single run between manifold and each location. Once in the room I split down with tees to bath, shower, sink and toilet.

 

12 minutes ago, markharro said:

What is the relevance of running 15mm pipes?

Smaller than 22mm which the plumber may use as a header, big enough to supply the bath with good etc.

 

13 minutes ago, markharro said:

explain what "hot water circulation" is?

Basically a  secondary pipe in the hot water system. A pump, timer and thermostat, takes hot water from cylinder and pushes it around the domestic hot water system, so the pipe and water is hot prior to the water coming out of the tap. Our furthest tap is 18m from the cylinder, we have the pump on in the morning and evening, within a second or so, warm water comes out of the tap. Costs almost nothing to run so long as it's only running when you need it on.

[Iceverge]

33 minutes ago, markharro said:

MDPE brings the water into the house to the main stopcock?

 

Yes. 

33 minutes ago, markharro said:

whats a "control block"?

Maybe the right name is something else. 

 

33 minutes ago, markharro said:

radial" - does that mean separate pipes to each location needing a cold supply?

 

Yes like a spider with a pipe for each outlet. 

 

33 minutes ago, markharro said:

How does a "standard" circuit compare - does that have one main pipe in a circuit with Ts off to each room?

 

It's like the branches of a tree where a big pipe splits off into smaller ones to feed outlets. You end up with lots of joints but less pipes. Unfortunately this means you have lots of joints hidden and inaccessible. You also have large deadlegs and can have flow rate issues as lots of outlets are fed from the same pipe. 

33 minutes ago, markharro said:

UVC

UnVented Cylinder. 

 

33 minutes ago, markharro said:

So 10mm pipe only for hot water supplied to far off locations - is the logic that this gets the water there fast and minimises wasted heat loss from a smaller volume in the pipe? 

 

All basins. I did it for the kitchen tap too as it was a 13m run. It did limit the hot water to 6l/min though rather than 10l/min with a 15mm to have a quicker delivery of hot water. 

33 minutes ago, markharro said:

So 15mm would be the norm for shorter hot water feeds? Is that enough throughput for showers

 

Loads yes. 

[Iceverge]

19 minutes ago, JohnMo said:

It all becomes very simple, no hidden joints, single run between manifold and each location. Once in the room I split down with tees to bath, shower, sink and toilet.

 

 

If I was to do it again I would have a rule that no joint should be inaccessible and should any joint fail it could safely drain into a floor drain. In this case Tees in a bathroom with a wetroom floor for instance would be fine. 

 

20 minutes ago, JohnMo said:

Our furthest tap is 18m from the cylinder, we have the pump on in the morning and evening, within a second or so, warm water comes out of the tap. Costs almost nothing to run so long as it's only running when you need it on.

 

Had we been a bit more savvy with the UVC location we could have had a 4m run to the kitchen tap and less than 6m to the basins. No circulation loop needed or long runs. Hot dead legs to the showers and baths make no difference with such large flow rates and longer run times. 

[joe90]

10mm for basins is more than adequate and less dead leg and time and water wasted waiting for hot water.

[markharro]

1 hour ago, JohnMo said:

It all becomes very simple, no hidden joints, single run between manifold and each location. Once in the room I split down with tees to bath, shower, sink and toilet.

So for the typical bath/showerroom with hot water needed for both basin and shower/bath how would you run 10mm to basin on this radial solution? 15mm to the room then split with 10mm to basin and 15mm to shower/bath? Or do you have 2 radial feeds to the single room - 1 at 10mm for the basin and the other 15mm for shower/bath?

[JohnMo]

56 minutes ago, markharro said:

shower/bath how would you run 10mm to basin on this radial solution? 15mm to the room then split with 10mm to basin and 15mm to shower/bath? Or do you have 2 radial feeds to the single room - 1 at 10mm for the basin and the other 15mm for shower/bath?

I kept it simple just 15mm everywhere.

 

Image of shower room, no bath in this room.

 

Hot water pipes come from cieling cold out of floor.

 

Two curved vertical pipes are to shower.

[JohnMo]

Manifold looks like this, main stop cock at lower right corner, to the left is the pipe and isolator outside tap, bigger white pipe takes water up to plant room

[Iceverge]

 

 

Here's a diagram of mine..

 

 

And a Pic. 

 

 

Things I would change.....

On @Nickfromwales advice avoid compression fixings of Hep2o pipes although I've had no issues yet. 

 

The Multiblock heats via convention from the thermostatic control valve (screwed directly onto the top of the tank) as it is higher than the top of the tank. 

 

This should be lower. 

 

Note the hot manifold and the 10mm pipes with the first draw off. It is preheated via convection and there's super speedy hot water to the basin taps. 

 

I only insulated the hot manifold as the Hep pipes contain almost no water and it cools instantly once switched off in any case with or without insulation. 

 

I should have tanked the floor and put in a floor drain too. 

 

I could have ran 10mm cold to the W/C cisterns and the basin taps too but fittings and manifolds were cheaper for the 15mm. 

 

 

 

[Thorfun]

here's mine

 

 

quite a lot of useful information in the thread about hep2o plumbing and manifolds as well as other examples of manifold systems too. plus lots of other aspects of plumbing. I've a feeling I'll be adding to it soon with more question too!

 

I didn't insulate any pipework after my manifolds. I don't know if that's a good or bad thing and the house isn't finished yet so I probably won't know for quite a while yet.

[markharro]

Thanks for the various answers so far....this has helped a lot to focus my plans. 

 

So from what everyone has said so far I am convinced by the radial system. There are some finer tuning points I don't quite have my head around yet though.

 

1 In the kitchen we will have a sink and dishwasher. If we wanted to feed the DW with hot water from the hot water cylinder does that mean we need a separate pipe to it? If so would a 10mm do?

2 Back to the shower-room. My better half has her heart set on what will be a shower capable of a very high flow rate. More than I think 15mm will service. If she persists with this would this need its own radial supply or higher bore than 15mm with another 10mm for the basin?

3 In our utility room we will have a sink and washing machine. First of all are WMs connected to a hot feed? If so, will one pipe with a T serve sink and WM? Will 10mm suffice?

 

thanks

[DamonHD]

Do any of the dishwashers that you would consider actually have hot fill?  In most cases new models don't in part because heating directly at the point of use is better in several regards.

 

Rgds

 

Damon

Edited August 5, 2023 by DamonHD

[markharro]

Hi @DamonHD yes apparently Miele ones do or at least some of them - their website states it can save up to 50% in energy costs....as we are installing PV and an ASHP it seems a good option albeit I expect its not going to be £££ savings.

[JohnMo]

Our dishwasher takes hot water, but it only really works if the dishwasher goes on as soon as you have finished using the hot tap. Otherwise the water draw is too small to get hot water in to the dishwasher.

 

12 minutes ago, markharro said:

their website states it can save up to 50% in energy costs

50% compared to what and when

[Nickfromwales]

18 minutes ago, DamonHD said:

Do any of the dishwashers that you would consider actually have hot fill?  In most cases new models don't in part because heating directly at the point of use is better in several regards.

 

Rgds

 

Damon

All except when the hot water is FOC from solar?

[Iceverge]

30 minutes ago, markharro said:

In the kitchen we will have a sink and dishwasher. If we wanted to feed the DW with hot water from the hot water cylinder does that mean we need a separate pipe to it? If so would a 10mm do

 

If it was me and I had a floor drain under the cupboards in the kitchen I would use be happy to Tee off the 15mm to the hot tap. 

 

33 minutes ago, markharro said:

Back to the shower-room. My better half has her heart set on what will be a shower capable of a very high flow rate. More than I think 15mm will service. If she persists with this would this need its own radial supply or higher bore than 15mm with another 10mm for the basin

 

Get her to define this please in litres per minute. If needed take a measuring jug and a stopwatch to the bathroom. Infact this is a really good exercise with all your current taps whereever you're living now. Time to hot and litres per minute. It'll let you make some informed decisions.

Our shower at 10l/min is more than adequate for Mrs and she has very thick hair. 15mm for the shower. 

 

I would keep all basin hots as dedicated 10mm runs. They only flow at about 4l/min so a 10m run of 15mm pipe would take 20 seconds to hot while a 10mm would take about 7seconds to hot. 

 

39 minutes ago, markharro said:

In our utility room we will have a sink and washing machine. First of all are WMs connected to a hot feed? If so, will one pipe with a T serve sink and WM? Will 10mm suffice?

 

I would run 15mm to the utility tap and T 15mm to the WM. Only some WM have a hot feed but it's worth it if you can. 

 

Similarly with a dishwasher which only use about 6l of water. (Much less than hand washing) Even with a large deadleg of 2l you're still saving, presuming you heat your hot water via an ASHP or solar. 

 

Don't worry if you buy a dishwasher without this though. You can just run it when PV output is high or on a cheap time of use tarrif.