water supply fixture unit for unique plumbing fixtures 2

Dear all,
i'm trying to find the water supply fixture unit (wsfu) for some laboratory equipment like (sterilizer, rack washer ,... etc) which is not listed in any plumbing code

i know that to determine the water supply pipe size for group of fixtures i need to add the wsfu values the convert to equivalent flow rate. the water consumption for each individual equipment is known from the manufacturer sheet. please advice.

 

[PEDARRIN2]

Please place future plumbing related posts in the Plumbing Engineering Forum.

A general rule of thumb is to equate 1 gpm with 2 fixture units. This is based on sanitary sizing, but the philosophy is what comes out of a water supply generally goes out the drain.

If the equipment is used on a fairly consistent basis, I have also calculated the fixture units for the other fixtures, calculated a gpm and then added the published flow from the equipment. That is a bit conservative, but it works.

 

[bimr]

Contact the manufacturers of this equipment.

 

[Mr.zoro]

Thank you guys for your help . I really appreciate that

i'd also be grateful for more ideas about that

the problem is not to size the branch for one equipment individually but it is how to determine the pipe size for group of such different unique equipment that needs water supply.i can't use the water consumption rate mentioned in the product catalog because the water supply usage is intermittent so i need to get wsfu value to add to get the total then determine the flow rate.

 

[PEDARRIN2]

Remember, fixture units are only statistical use numbers to help in sizing.

Talk to the users of the equipment and see how often (and which equipment) could be used simultaneously.

Also, if you can, see how many people could be working in the area at the same time. If there are only two people, then you can size the piping for the two largest users and that would be realistic. Be conservative, but not overly so. The difference might be a single pipe size and even if you are smaller, it will likely not matter much since the equipment is used intermittently.

 

[Mr.zoro]

I tried to get data about the people but it is not available
beside i can't assume by myself.
the only method mentioned in most codes is to add all water supply fixture unit values to get the demand and we only add only the gpm with the continuous flow.

another issue i want to ask about if we get the total wsfu for water riser, can i multiply the demand with diversity factor on the grounds that not all fixtures will be used at the same time.

 

[PEDARRIN2]

Since most lab equipment, i.e. sterilizers, rack washers, and the like are basically "fill up the tank" type of equipment, you can size the pipe to the equipment using the volume of the tank and size the pipe so that volume is filled in 1-2 minutes without exceeding 5 ft/s velocity on the pipe. Upstream pipe would be sized based on the gpm from fixture units from other items added to the gpm determined previously. If you go far enough upstream, the probability and the fixture units will overshadow any actual flow (within reason) and you can use the 1 gpm/fixture unit conversion.

With fixture units, I use Hunter's curve to arrive at a flow and then multiply by 0.7 to account for low flow fixtures. You will have to determine what is a good diversity factor for your facility.

 

[Mr.zoro]

thank you PEDARRIN2 for your help

 

[Mr.zoro]

ARE THERE ANY OTHER SOLUTIONS FOR THIS ISSUE ?

 

[dbill74]

Because they vary so much, there is no definitive guide for designing plumbing systems for labs.

Pedarrin2 has the right approach and is basically what I do.
Sterilizers and rack washers act more like dish washers and clothes machines than anything if you 'must' assign WSFU. Realistically though, get a flow rate from a cut sheet and add that to your gpm determined from WSFU tables for sizing your builgin main.

For piping in the lab, learn all you can about the equipment and how it is used. Then using the largest equipment connection size as a minimum, start increasing pipe size from there based on flow and a diversity factor. The diversity factor is something you will have to come up with on your own based on discussions with the client and operation of the equipment.

Depending on the client, make a record of your assumptions.