p.r.v.from combi boiler

[desrob]

can the pipe work from the boiler go immediatly vertical

 

[Billy Bob Bob]

no not under any circumstances it must always fall away from the boiler

 

[desrob]

common sense tells you it should fall away,but expanded water still will discharge

 

[Billy Bob Bob]

yes but in theory it could take the heat exchanger with it

 

[desrob]

came across it today,pointed it out as incorrect,and was told to show were in m.i it says it can not be done

 

[Billy Bob Bob]

on the performa mi it says must have a continuous fall from boiler,i have come across a few that go trough the flue hole but as a general rule they must be lower than the prv

 

[plumbster3456]

why can a prv not go straight down gas man? of course it can it may not be the right way but I would not say it cant be done.

 

[Billy Bob Bob]

strait down is a continuous fall ,thought we were talking about it riseing

 

[desrob]

i think you got mixed up plumbster,he,s not saying that

 

[tamz]

Seen lots that rise and go through beside the flue and a couple that rise and run across lofts. Tbh it wouldn't bother me too much.
Some MI don't say anything to contradict this method and some say it must fall.
Vaillant used to agree this could be done if a drain valve was fitted to the low point.

 

[buryboy]

Not clear on this, is the situation. In this instance does that p.r.v. copper discharge pipe after leaving the boiler go vertically up or vertically down?

Can't think of any M.I. that recomend going upwards at all. I would think there should be little or no resistance in that pipe to getting any hot discharge water out of and away from the boiler quickly.

Also quite a few p.r.v.'s discharge pipes drip/leak a little and if the pipe was vertically up then as this slowly filled up it could act as a plug should a hot discharge occur at any time leading to what consequence?

 

[gasmarc]

going down is the correct way with no trap being possible , i did get pulled up on a job before for having it rise up about 6 inches, if a boiler is in a basement this can be a problem i have just run the prv under the floor other wise it would have been major agg or a sump pump which is an expensive way of doing things

 

[plumbster3456]

ahh I see gas man I totally agree with you now. I would never do a blow off that rises up wow this is crazy cowboy stuff.
and tamz have you actually seen one go out beside a flue lol there is no hope for the guy who done that he should be on rogue traders
I have seen some crazy stuff myself before such as no prv even connected to pipework but never before a prv / blow off that rises wow.

 

[tamz]

I've seen loads going out through the same hole as the flue, usually in tenement buildings where the walls are 30+" thick and i've come across a couple that went up and over the loft where the boiler was fitted in the middle of the house with a vertical flue.
As i said it doesn't bother me too much if i see it. It may not be correct but it will still work even if it was sitting full of water. Just like a P trap on a sink works, with no pressure to push it. There is the argument that it could block but that could be overcome by upsizing the pipe.
Vaillant used to agree it could be done but recommended a drain valve be fitted to the lowest point.

When sealed systems were first being fitted in the 80's i was working doing contract installs for BG. Their recommended way of terminating at the time was drop it to the floor and if you ever are in a plant room anywhere you will find 95% of them like that.

 

[plumbster3456]

yes seen many of them in plant rooms for new build schools / hospitals they just terminate on the floor of the room but this is ok as there is always a gully to take the water away.
the difference is the prv is coming off 42mm or 54mm pipe so a lot bigger prv used.
Glad I have never had to take one through the flue hole its just as easy to buy a long drill bit as you can use it for all sorts such as outside taps , holes for prv blah blah blah

 

[shelley.sidney]

Depends on type u have.
mine has 2 taps/levers on pipes just below.
i have to open both till pressure builds up then close them!!!.

 

[plumbster3456]

Depends on type u have.
mine has 2 taps/levers on pipes just below.
i have to open both till pressure builds up then close them!!!.

that is a filling loop best you stick to cleaning up the house

 

[gasmarc]

i didnt get that at first ,nice one lol

 

[Bernie2]

Hmm!

What if the water freezes in the prv overflow and the boiler prv tries to blow off? Big bang!

 

[gasmarc]

yes I remember someone saying they were on a job before where the expansion vessel blew up embedding it self into a wall

 

[plumber0808]

can go up by using a prv kit,
tee it into the heating then fit another prv terminating at a higher level allowing it to fall, manufacturer can supply the kit along with installation instructions