Backflow prevention

[d000hg]

We were blindsided by this issue - since our new building has commercial use our water board mentioned that any washing machine must utilise an air-gap to prevent contamination. So we've been looking into it.

WRAS have a helpful article here: https://www.wras.co.uk/news/wras_news/categories/installer_news/plumbing_in_appliances/

WRAS seems to say that for commercial buildings we need cat 4 (or better) BF protection for washing machines and dishwashers. It seems a suitable valve unit would cost £2-300. I'm not sure if we need one per unit or can take multiple feeds?

However our water supplier say we need a commercial washing machine with air-gap since we will be washing reusable nappies. Such a machine costs £thousands, and looking around online a proper external cat-5 break-tank is not only very expensive but pretty large.

And then there are cat 5 "water interruption" valves which are very cheap (£60) but specifically say they may not be used for washing machines - not sure about dishwashers.

The WRAS page doesn't make any special note of what washing machines will be used for so can any experts help me out here? Ideally people who are WRAS/WIAPS/WaterSafe qualified (I don't know the difference) - our local authority are fairly hopeless so I really want to be able to tell them "we plan to do this is that OK" rather than ask them "what do we need" as far as possible.
Is this an area where different authorities have different rules or is it a national standard?

Thanks, sorry for long post.

 

[d000hg]

I should say this is for a small building/business, like a 2-bed bungalow. So getting in a big commercial, certified plumber is not necessarily practical. We had expected to use a local firm and get the water authority to do an inspection.

 

[bernardgreen]

I would have thought that gravity feeding the appliances from a cold water storage tank ( cistern ) with a ball cock valve would ensure an air gap.

A ball cock valve with the outlet of the valve at least 5 inches above the surface of the water. In the event the valve fails to shut then the over flow would need to prevent the water level getting closer tha 5 inches from the valve.

EDIT just seen that there is a diagram of this in the WRAS article linked to.

 

[d000hg]

Cheers Bernard. The principle seems sound though it seems a bulky solution and of course you will lose any decent water pressure; I don't think washing machines can work from low-pressure supplies?

It seems anything you use has to be WRAS-approved so I am not sure if you can just build one, or must buy a special product like this (which also incorporates a pump to regain lost pressure): https://www.flowstarvalveshop.com/collections/all/products/cat-5-break-tank-pump
My initial research shows this will cost several grand, which is simply prohibitive.

 

[Madrab]

For your application then the Cat 5 classification will need an AA/AB air gap, only thing that will cover your requirement and the only way it would be achieved is to have an open topped cistern with either an un-restricted overflow or a slotted weir overflow. Ultimately the water cannot be allowed to get anywhere near the feed.

Once that's set up then you could pump the supply to the appliances, or if it's high enough above the appliances you may get away with it. without pumping

 

[d000hg]

Cheers @Madrab - though it's not what we really wanted to hear Can you explain why you think we need Cat 5? From what I've seen, even commercial laundry premises only require Cat 4 (though they would probably use commercial machines with it built in). I thought Cat 5 was restricted for hospitals and the like.

Does an open-topped cistern mean it has to be literally open to the air, I can understand the need for an unrestricted overflow but what is this about? Is it so that in case of a blocked overflow the tank will literally overflow on the floor before it can reach the feed?

Any idea if you can install this using simple components - I've seen prices up to £10k! It seems in principle all we really need is a toilet cistern (toilets also have backflow restrictions) with a pumped outlet?!

 

[Madrab]

Sorry, I was taking from your information, in the main, that you were looking at CAT5 BF equipment. Even then CAT4 is up there along the same line as far as Backflow is concerned. That being said all it does is reduce the requirement from a free flow overspill to have an AA/AB air gap and you can drop it to an AF which would allow a standard cold water cistern with a protected 40mm overflow.

Is it so that in case of a blocked overflow the tank will literally overflow on the floor before it can reach the feed?

It's not a blocked overflow though, they don't have overflows, the spillover/weir channel is the overflow. It's all about removing any chance that the water in the cistern can reach the mains feed. Usually AA/AB cisterns sit in a catch tank that has a channel/overflow running externally

It seems in principle all we really need is a toilet cistern

yes, if it is fed by another interposed cistern that has an AG air gap, it cannot be fed by the mains. A toilet differs in that it has it's primary CAT5 air gap from the flush valve to the cistern be it through a flush tube or a closed coupled connection. Using this method though it can only be gravity fed.

 

[d000hg]

The big difference for Cat 4 seems to be you can get away with an RPZ valve which appears much cheaper and simpler from the little I've read.

Like: https://www.flowstarvalveshop.com/c...l-ba295s-class-4-backflow-preventer-rpz-valve

I don't know what all those bits do but it sounds perfect from the description.

 

[CBW]

Your water undertaker is responsible for enforcing the regulations, so if they want cat 5 backflow protection then that’s what you need to adhere to. Wras are an advisory scheme to advise, however like I said the water undertaker (waterboard as your calling them) determine what protection they want. Fluid category 5 exists in domestic premises - such as foul waste, and requirement is that a domestic shower hose can’t come into contact with the wc pan (fluid category 5) and other preventions.

 

[Madrab]

A reduced pressure zone valve (RPZ) allows for any water that may backflow, due to a drop in the supply pressure, to be emptied out of the valve and down into the waste/drain. It does need approval and BC sign off, it also need a suitably qualified/experienced installer (Water Regs) to fit it.

That being said then it can be a much easier solution if all you require is a streamlined inline option. Cheaper .... not necessarily, RPZ valves are not cheap, nor is the installation/notification/sign off.

 

[muggles]

Your water supplier is the ultimate arbiter, and if they say Cat 5 is needed then Cat 5 is needed. There are some commercial washing machines which fulfill the requirement on their own, without additional kit.

RPZ valves only protect to Cat 4 as you know, and they aren't the simple solution they may seem. They require annual maintenance and recalibration by a qualified person, which on its own can be quite expensive and over time would cost more than a commercial machine

 

[d000hg]

Your water supplier is the ultimate arbiter, and if they say Cat 5 is needed then Cat 5 is needed. There are some commercial washing machines which fulfill the requirement on their own, without additional kit.

RPZ valves only protect to Cat 4 as you know, and they aren't the simple solution they may seem. They require annual maintenance and recalibration by a qualified person, which on its own can be quite expensive and over time would cost more than a commercial machine

So the water supplier isn't accountable to any national standards they just decide what they want and that's that!?

A commercial washer is multiple thousands and while long term that might work out cheaper, the initial outlay is huge for a tiny business. It all seems a bit onerous, we might have to rethink having one at all.

We've asked the water guys to come out and visit and tell us exactly what they require so we'll see. At a very minimum it appears cat 4 is a requirement for any commercial building use no matter what else, but we don't have space for large tanks for instance for a dishwasher to have a break tank.

I wonder how commercial machines meet these standards, do they have internal break tanks?

 

[muggles]

Setting up a business is expensive. I know, I've been there...

The Electrolux WE170P complies, and can be had for about £1200. There's even a reconditioned one on eBay for £450.

They have internal Type AB air gaps and unrestricted weir overflows in order to comply. You can't use detergents with a greater fluid cat risk than 3, as the detergent is introduced before the air gap. This is common across most commercial machines

 

[d000hg]

Cheers @muggles that is actually a LOT less than I was led to believe - that's high-end domestic pricing where I'd been advised we were talking multiple thousands.
If this is an indicative price for a decent product (?) then I would tend to agree that by the time you've bought even a cat-4 RMZ for £200 and had it installed on your regular washer, you're only saving maybe £500 up-front (rather than a couple of grand as I had thought). And that's assuming you were buying quite a cheap domestic unit.
Do these machines just plug in like normal and all the magic is inside or is there any special plumbing to do?

The other thing we're looking at is dishwashers. I'm finding it hard to even tell what rating these have - I think they are typically assumed cat-3 but none of my googling has found anything helpful. I doubt we'd get away with this although it wasn't mentioned when we spoke to the water company, perhaps they might be persuaded since rinsing a few plates that were just used is very different from washing sh***y clothes

 

[muggles]

Reading the instructions online, it would seem that they are just plug and play. You need both hot and cold supplies.

I suspect the Cat5 requirement for you is because you've been classed as a "healthcare establishment". This is a fairly broad term which encompasses day care and residential care centres. Catering establishments get away with Cat4, healthcare is Cat 5, and yes your dishwasher needs to be Cat 5 too.