Confused about my system - check valves needed on bath supply?

[realnovice43]

I wonder if you knowledgeable people could help me out please?



House built in 1995 with gravity fed hot water and I was told at the time by the site manager that the bathroom cold water comes direct off the mains - saw no reason to query this. Updating the bath taps in ensuite and main bathroom with deck mixers with shower attachment to wash hair (for low pressure) prior to sale I thought this must be an unbalanced supply. I read the info about the need to install check valves despite the fact that none are in place 9and I found a leaflet in the loft dating back to 95 which mentions them for certain applications) - so I bought all the parts.



Then I looked in the loft to check about shutting off the supply and found 3 tanks fed from a 15 mm cold feed – one of which is obviously the header for the CH. The middle tank has feeds off it to the shower in main bathroom plus feeds for the hot - and to my surprise the cold - supplies in the baths in each bathroom. So my thought is that this is actually a balanced system – at least for the baths if not the basins- and so no check valves needed on the baths. I believe that in this case the air gap at the tank would prevent any backflow problems even thought water mixes in the spout of the mixer.


Am I correct in my understanding of my system or if not which supplies need check valves and what sort (single/double)? I am competent at basic plumbiing stuff but I don't want to start attacking the pipework with my pipe slice unless I really need to!!

 

[WHPES]

If everything is fed from the cisterns (proper name for your tanks) then you are correct that you don't need check valves. In fact fitting them would probably prevent your system from working properly.

The baths are fed from the cisterns as they were fitted with shower mixers. Recommend leave as they are but make sure you use low pressure suitable fittings.

Your house is quite an old fashioned set-up. Nowadays your house would have been fitted with an unvented cylinder for the hot, with the cold fed from the mains.

Where people get problems is where they put gravity to one side of a shower or mixer tap and mains to the other. The usual result is that it doesnt work.

 

[jase158]

Try turning mains off and open kitchen tap, when this runs dry, try each tap in house and see if water comes out or not, if no water then it is mains fed, if water comes out then mains fed.

However, your taps have a air gap, which acts as a backflow prevention, so no need for non return valves,

however if they are mixing taps, then not sure if needed or not.

 

[realnovice43]

Thanks very much for the info -there's so much about this on the internet but it can be contradictory. I didn't really want to start cutting the bath feeds as the original plumbers installed the traps sitting into a hole in the the boarded floor and there's plenty of opportunity for the water to run into the void and down the wall below as I found out when I had to dismantle the leaking popup waste they hadn't fitted properly (it was a Friday afternoon job judging by the silicone liberally applied everywhere including the tap connections to the tails).

Appreciate this is an antiquated design!! Does this mean that the cold supplies to the basins are also fed from the cisterns - teed off the bath feeds somewhere or separate pipe runs? In which case here again no check valves needed for a low pressure mixer?

 

[tamz]

Do as Jase said and shut the main stopcock. Anything else still running is tank fed.

 

[AWheating]

mixer taps only require check vavles if the tap mixes the hot and cold in the tap or spout. If the tap has two seperate spouts then no check valves are required normally. If the feeds are from tanks then non are required as the cold main is protected by the air gap in the tank.

Realnovice i can not believe its took you 15plus years to go up into your loft ?

 

[realnovice43]

Haha:smug2: I did venture up but deliberately avoided going near the tanks - it's dark down there - never know what you might find!

One of the mixer taps I'm replacing had separate flow for hot and cold but the other (one of those goldy victoriana type things that builders liked putting in way back then) does mix in the spout with no check valves. When I read the installation instructions for the new one I started thinking about how the supplies were set up and the issue of backflow which frankly had never occurred to me. Combined with the duff info i got from the site guy is why I got concerned about the check valves and ventured up to suss it out.

The bath feeds definitely come from the tank - seen them and followed them. So I understand from what you guys say even though these new mixers combine hot and cold in the spout I don't have to fit check valves to the baths.

Been out today and going to have a look at tracing the cold feed to the basins when I have time tomorrow - guess if I can't it wouldn't hurt to put a single check valve on the basin cold feed if mixer that mixes in the spout has to go in there even if it is tank fed? The flow is pretty strong.

Thanks for all the help

 

[fuzzy]

mixer taps only require check vavles if the tap mixes the hot and cold in the tap or spout. If the tap has two seperate spouts then no check valves are required normally. If the feeds are from tanks then non are required as the cold main is protected by the air gap in the tank.

Realnovice i can not believe its took you 15plus years to go up into your loft ?

sometimes they come with them but possibly not.

buy two check valves if off the mains, if unba;anced supply it wont be suitable for a mix inbody type